QGIS 用户指南


QGIS User Guide Release 2.6 QGIS Project January 27, 2015 Contents 1 Preamble 3 2 Conventions 5 2.1 GUI Conventions...........................................5 2.2 Text or Keyboard Conventions....................................5 2.3 Platform-specific instructions....................................6 3 Foreword 7 4 Features 9 4.1 View data...............................................9 4.2 Explore data and compose maps...................................9 4.3 Create, edit, manage and export data................................. 10 4.4 Analyse data............................................. 10 4.5 Publish maps on the Internet..................................... 10 4.6 Extend QGIS functionality through plugins............................. 10 4.7 Python Console............................................ 11 4.8 Known Issues............................................. 11 5 What’s new in QGIS 2.6 13 5.1 Application and Project Options................................... 13 5.2 Data Providers............................................ 13 5.3 Map Composer............................................ 13 5.4 QGIS Server............................................. 14 5.5 Symbology.............................................. 14 5.6 User Interface............................................ 14 6 Getting Started 15 6.1 Installation.............................................. 15 6.2 Sample Data............................................. 15 6.3 Sample Session............................................ 16 6.4 Starting and Stopping QGIS..................................... 17 6.5 Command Line Options....................................... 17 6.6 Projects................................................ 19 6.7 Output................................................ 19 7 QGIS GUI 21 7.1 Menu Bar............................................... 22 7.2 Toolbar................................................ 27 7.3 Map Legend............................................. 27 7.4 Map View.............................................. 30 7.5 Status Bar............................................... 30 i 8 General Tools 31 8.1 Keyboard shortcuts.......................................... 31 8.2 Context help............................................. 31 8.3 Rendering.............................................. 31 8.4 Measuring.............................................. 33 8.5 Identify features........................................... 35 8.6 Decorations.............................................. 36 8.7 Annotation Tools........................................... 38 8.8 Spatial Bookmarks.......................................... 39 8.9 Nesting Projects........................................... 41 9 QGIS Configuration 43 9.1 Panels and Toolbars......................................... 43 9.2 Project Properties........................................... 44 9.3 Options................................................ 44 9.4 Customization............................................ 52 10 Working with Projections 55 10.1 Overview of Projection Support................................... 55 10.2 Global Projection Specification................................... 55 10.3 Define On The Fly (OTF) Reprojection............................... 57 10.4 Custom Coordinate Reference System................................ 58 10.5 Default datum transformations.................................... 59 11 QGIS Browser 61 12 Working with Vector Data 63 12.1 Supported Data Formats....................................... 63 12.2 The Symbol Library......................................... 75 12.3 The Vector Properties Dialog.................................... 79 12.4 Expressions.............................................. 105 12.5 Editing................................................ 112 12.6 Query Builder............................................ 129 12.7 Field Calculator........................................... 130 13 Working with Raster Data 133 13.1 Working with Raster Data...................................... 133 13.2 Raster Properties Dialog....................................... 134 13.3 Raster Calculator........................................... 142 14 Working with OGC Data 145 14.1 QGIS as OGC Data Client...................................... 145 14.2 QGIS as OGC Data Server...................................... 154 15 Working with GPS Data 159 15.1 GPS Plugin.............................................. 159 15.2 Live GPS tracking.......................................... 163 16 GRASS GIS Integration 169 16.1 Starting the GRASS plugin..................................... 169 16.2 Loading GRASS raster and vector layers.............................. 170 16.3 GRASS LOCATION and MAPSET................................. 170 16.4 Importing data into a GRASS LOCATION............................. 172 16.5 The GRASS vector data model................................... 173 16.6 Creating a new GRASS vector layer................................. 174 16.7 Digitizing and editing a GRASS vector layer............................ 174 16.8 The GRASS region tool....................................... 177 16.9 The GRASS Toolbox......................................... 177 ii 17 QGIS processing framework 187 17.1 Introduction............................................. 187 17.2 The toolbox.............................................. 188 17.3 The graphical modeler........................................ 197 17.4 The batch processing interface.................................... 203 17.5 Using processing algorithms from the console........................... 205 17.6 The history manager......................................... 210 17.7 Writing new Processing algorithms as python scripts........................ 211 17.8 Handing data produced by the algorithm.............................. 213 17.9 Communicating with the user.................................... 213 17.10 Documenting your scripts...................................... 213 17.11 Example scripts........................................... 214 17.12 Best practices for writing script algorithms............................. 214 17.13 Pre- and post-execution script hooks................................. 214 17.14 Configuring external applications.................................. 214 17.15 The QGIS Commander........................................ 221 18 Processing providers and algorithms 223 18.1 GDAL algorithm provider...................................... 223 18.2 LAStools............................................... 256 18.3 Modeler Tools............................................ 281 18.4 OrfeoToolbox algorithm provider.................................. 283 18.5 QGIS algorithm provider....................................... 358 18.6 R algorithm provider......................................... 412 18.7 SAGA algorithm provider...................................... 422 18.8 TauDEM algorithm provider..................................... 593 19 Print Composer 625 19.1 First steps............................................... 626 19.2 Rendering mode........................................... 630 19.3 Composer Items........................................... 631 19.4 Manage items............................................. 653 19.5 Revert and Restore tools....................................... 654 19.6 Atlas generation........................................... 656 19.7 Creating Output........................................... 658 19.8 Manage the Composer........................................ 659 20 Plugins 661 20.1 QGIS Plugins............................................. 661 20.2 Using QGIS Core Plugins...................................... 665 20.3 Coordinate Capture Plugin...................................... 665 20.4 DB Manager Plugin......................................... 666 20.5 Dxf2Shp Converter Plugin...................................... 667 20.6 eVis Plugin.............................................. 668 20.7 fTools Plugin............................................. 678 20.8 GDAL Tools Plugin......................................... 681 20.9 Georeferencer Plugin......................................... 684 20.10 Interpolation Plugin......................................... 688 20.11 Offline Editing Plugin........................................ 689 20.12 Oracle Spatial GeoRaster Plugin................................... 690 20.13 Raster Terrain Analysis Plugin.................................... 692 20.14 Heatmap Plugin........................................... 693 20.15 MetaSearch Catalogue Client.................................... 696 20.16 Road Graph Plugin.......................................... 700 20.17 Spatial Query Plugin......................................... 701 20.18 SPIT Plugin............................................. 702 20.19 SQL Anywhere Plugin........................................ 703 20.20 Topology Checker Plugin...................................... 703 20.21 Zonal Statistics Plugin........................................ 707 iii 21 Help and Support 709 21.1 Mailing lists............................................. 709 21.2 IRC.................................................. 710 21.3 BugTracker.............................................. 710 21.4 Blog................................................. 711 21.5 Plugins................................................ 711 21.6 Wiki................................................. 711 22 Appendix 713 22.1 GNU General Public License.................................... 713 22.2 GNU Free Documentation License................................. 716 23 Literature and Web References 723 Index 725 iv QGIS User Guide, Release 2.6 . . Contents 1 QGIS User Guide, Release 2.6 2 Contents CHAPTER 1 Preamble This document is the original user guide of the described software QGIS. The software and hardware described in this document are in most cases registered trademarks and are therefore subject to legal requirements. QGIS is subject to the GNU General Public License. Find more information on the QGIS homepage, http://www.qgis.org. The details, data, and results in this document have been written and verified to the best of the knowledge and responsibility of the authors and editors. Nevertheless, mistakes concerning the content are possible. Therefore, data are not liable to any duties or guarantees. The authors, editors and publishers do not take any responsibility or liability for failures and their consequences. You are always welcome to report possible mistakes. This document has been typeset with reStructuredText. It is available as reST source code via github and online as HTML and PDF via http://www.qgis.org/en/docs/. Translated versions of this document can be downloaded in several formats via the documentation area of the QGIS project as well. For more information about contributing to this document and about translating it, please visit http://www.qgis.org/wiki/. Links in this Document This document contains internal and external links. Clicking on an internal link moves within the document, while clicking on an external link opens an internet address. In PDF form, internal and external links are shown in blue and are handled by the system browser. In HTML form, the browser displays and handles both identically. User, Installation and Coding Guide Authors and Editors: Tara Athan Radim Blazek Godofredo Contreras Otto Dassau Martin Dobias Peter Ersts Anne Ghisla Stephan Holl N. Horning Magnus Homann Werner Macho Carson J.Q. Farmer Tyler Mitchell K. Koy Lars Luthman Claudia A. Engel Brendan Morely David Willis Jürgen E. Fischer Marco Hugentobler Larissa Junek Diethard Jansen Paolo Corti Gavin Macaulay Gary E. Sherman Tim Sutton Alex Bruy Raymond Nijssen Richard Duivenvoorde Andreas Neumann Astrid Emde Yves Jacolin Alexandre Neto Andy Schmid Hien Tran-Quang Copyright (c) 2004 - 2014 QGIS Development Team Internet: http://www.qgis.org License of this document Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Docu- mentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in Appendix GNU Free Documentation License. . 3 QGIS User Guide, Release 2.6 4 Chapter 1. Preamble CHAPTER 2 Conventions This section describes the uniform styles that will be used throughout this manual. 2.1 GUI Conventions The GUI convention styles are intended to mimic the appearance of the GUI. In general, a style will reflect the non-hover appearance, so a user can visually scan the GUI to find something that looks like the instruction in the manual. • Menu Options: Layer → Add a Raster Layer or Settings → Toolbars → Digitizing • Tool: Add a Raster Layer • Button : [Save as Default] • Dialog Box Title: Layer Properties • Tab: General • Checkbox: Render • Radio Button: Postgis SRID EPSG ID • Select a number: • Select a string: • Browse for a file: • Select a color: • Slider: • Input Text: A shadow indicates a clickable GUI component. 2.2 Text or Keyboard Conventions This manual also includes styles related to text, keyboard commands and coding to indicate different entities, such as classes or methods. These styles do not correspond to the actual appearance of any text or coding within QGIS. • Hyperlinks: http://qgis.org • Keystroke Combinations: Press Ctrl+B, meaning press and hold the Ctrl key and then press the B key. • Name of a File: lakes.shp 5 QGIS User Guide, Release 2.6 • Name of a Class: NewLayer • Method: classFactory • Server: myhost.de • User Text: qgis --help Lines of code are indicated by a fixed-width font: PROJCS["NAD_1927_Albers", GEOGCS["GCS_North_American_1927", 2.3 Platform-specific instructions GUI sequences and small amounts of text may be formatted inline: Click File QGIS → Quit to close QGIS. This indicates that on Linux, Unix and Windows platforms, you should click the File menu first, then Quit, while on Macintosh OS X platforms, you should click the QGIS menu first, then Quit. Larger amounts of text may be formatted as a list: • Do this • Do that • Do something else or as paragraphs: Do this and this and this. Then do this and this and this, and this and this and this, and this and this and this. Do that. Then do that and that and that, and that and that and that, and that and that and that, and that and that and that, and that and that and that. Screenshots that appear throughout the user guide have been created on different platforms; the platform is indi- cated by the platform-specific icon at the end of the figure caption. . 6 Chapter 2. Conventions CHAPTER 3 Foreword Welcome to the wonderful world of Geographical Information Systems (GIS)! QGIS is an Open Source Geographic Information System. The project was born in May of 2002 and was estab- lished as a project on SourceForge in June of the same year. We’ve worked hard to make GIS software (which is traditionally expensive proprietary software) a viable prospect for anyone with basic access to a personal com- puter. QGIS currently runs on most Unix platforms, Windows, and OS X. QGIS is developed using the Qt toolkit (http://qt.digia.com) and C++. This means that QGIS feels snappy and has a pleasing, easy-to-use graphical user interface (GUI). QGIS aims to be a user-friendly GIS, providing common functions and features. The initial goal of the project was to provide a GIS data viewer. QGIS has reached the point in its evolution where it is being used by many for their daily GIS data-viewing needs. QGIS supports a number of raster and vector data formats, with new format support easily added using the plugin architecture. QGIS is released under the GNU General Public License (GPL). Developing QGIS under this license means that you can inspect and modify the source code, and guarantees that you, our happy user, will always have access to a GIS program that is free of cost and can be freely modified. You should have received a full copy of the license with your copy of QGIS, and you also can find it in Appendix GNU General Public License. Tip: Up-to-date Documentation The latest version of this document can always be found in the documentation area of the QGIS website at http://www.qgis.org/en/docs/. . 7 QGIS User Guide, Release 2.6 8 Chapter 3. Foreword CHAPTER 4 Features QGIS offers many common GIS functionalities provided by core features and plugins. A short summary of six general categories of features and plugins is presented below, followed by first insights into the integrated Python console. 4.1 View data You can view and overlay vector and raster data in different formats and projections without conversion to an internal or common format. Supported formats include: • Spatially-enabled tables and views using PostGIS, SpatiaLite and MS SQL Spatial, Oracle Spatial, vector formats supported by the installed OGR library, including ESRI shapefiles, MapInfo, SDTS, GML and many more. See section Working with Vector Data. • Raster and imagery formats supported by the installed GDAL (Geospatial Data Abstraction Library) library, such as GeoTIFF, ERDAS IMG, ArcInfo ASCII GRID, JPEG, PNG and many more. See section Working with Raster Data. • GRASS raster and vector data from GRASS databases (location/mapset). See section GRASS GIS Integra- tion. • Online spatial data served as OGC Web Services, including WMS, WMTS, WCS, WFS, and WFS-T. See section Working with OGC Data. 4.2 Explore data and compose maps You can compose maps and interactively explore spatial data with a friendly GUI. The many helpful tools available in the GUI include: • QGIS browser • On-the-fly reprojection • DB Manager • Map composer • Overview panel • Spatial bookmarks • Annotation tools • Identify/select features • Edit/view/search attributes • Data-defined feature labeling 9 QGIS User Guide, Release 2.6 • Data-defined vector and raster symbology tools • Atlas map composition with graticule layers • North arrow scale bar and copyright label for maps • Support for saving and restoring projects 4.3 Create, edit, manage and export data You can create, edit, manage and export vector and raster layers in several formats. QGIS offers the following: • Digitizing tools for OGR-supported formats and GRASS vector layers • Ability to create and edit shapefiles and GRASS vector layers • Georeferencer plugin to geocode images • GPS tools to import and export GPX format, and convert other GPS formats to GPX or down/upload directly to a GPS unit (On Linux, usb: has been added to list of GPS devices.) • Support for visualizing and editing OpenStreetMap data • Ability to create spatial database tables from shapefiles with DB Manager plugin • Improved handling of spatial database tables • Tools for managing vector attribute tables • Option to save screenshots as georeferenced images 4.4 Analyse data You can perform spatial data analysis on spatial databases and other OGR- supported formats. QGIS currently offers vector analysis, sampling, geoprocessing, geometry and database management tools. You can also use the integrated GRASS tools, which include the complete GRASS functionality of more than 400 modules. (See sec- tion GRASS GIS Integration.) Or, you can work with the Processing Plugin, which provides a powerful geospatial analysis framework to call native and third-party algorithms from QGIS, such as GDAL, SAGA, GRASS, fTools and more. (See section Introduction.) 4.5 Publish maps on the Internet QGIS can be used as a WMS, WMTS, WMS-C or WFS and WFS-T client, and as a WMS, WCS or WFS server. (See section Working with OGC Data.) Additionally, you can publish your data on the Internet using a webserver with UMN MapServer or GeoServer installed. 4.6 Extend QGIS functionality through plugins QGIS can be adapted to your special needs with the extensible plugin architecture and libraries that can be used to create plugins. You can even create new applications with C++ or Python! 4.6.1 Core Plugins Core plugins include: 1. Coordinate Capture (Capture mouse coordinates in different CRSs) 2. DB Manager (Exchange, edit and view layers and tables; execute SQL queries) 10 Chapter 4. Features QGIS User Guide, Release 2.6 3. Diagram Overlay (Place diagrams on vector layers) 4. Dxf2Shp Converter (Convert DXF files to shapefiles) 5. eVIS (Visualize events) 6. fTools (Analyze and manage vector data) 7. GDALTools (Integrate GDAL Tools into QGIS) 8. Georeferencer GDAL (Add projection information to rasters using GDAL) 9. GPS Tools (Load and import GPS data) 10. GRASS (Integrate GRASS GIS) 11. Heatmap (Generate raster heatmaps from point data) 12. Interpolation Plugin (Interpolate based on vertices of a vector layer) 13. Offline Editing (Allow offline editing and synchronizing with databases) 14. Oracle Spatial GeoRaster 15. Processing (formerly SEXTANTE) 16. Raster Terrain Analysis (Analyze raster-based terrain) 17. Road Graph Plugin (Analyze a shortest-path network) 18. Spatial Query Plugin 19. SPIT (Import shapefiles to PostgreSQL/PostGIS) 20. SQL Anywhere Plugin (Store vector layers within a SQL Anywhere database) 21. Topology Checker (Find topological errors in vector layers) 22. Zonal Statistics Plugin (Calculate count, sum, and mean of a raster for each polygon of a vector layer) 4.6.2 External Python Plugins QGIS offers a growing number of external Python plugins that are provided by the community. These plugins reside in the official Plugins Repository and can be easily installed using the Python Plugin Installer. See Section The Plugins Dialog. 4.7 Python Console For scripting, it is possible to take advantage of an integrated Python console, which can be opened from menu: Plugins → Python Console. The console opens as a non-modal utility window. For interaction with the QGIS en- vironment, there is the qgis.utils.iface variable, which is an instance of QgsInterface. This interface allows access to the map canvas, menus, toolbars and other parts of the QGIS application. For further information about working with the Python console and programming QGIS plugins and applications, please refer to http://www.qgis.org/html/en/docs/pyqgis_developer_cookbook/index.html. 4.8 Known Issues 4.8.1 Number of open files limitation If you are opening a large QGIS project and you are sure that all layers are valid, but some layers are flagged as bad, you are probably faced with this issue. Linux (and other OSs, likewise) has a limit of opened files by process. Resource limits are per-process and inherited. The ulimit command, which is a shell built-in, changes the limits only for the current shell process; the new limit will be inherited by any child processes. 4.7. Python Console 11 QGIS User Guide, Release 2.6 You can see all current ulimit info by typing user@host:~$ ulimit -aS You can see the current allowed number of opened files per proccess with the following command on a console user@host:~$ ulimit -Sn To change the limits for an existing session, you may be able to use something like user@host:~$ ulimit -Sn #number_of_allowed_open_files user@host:~$ ulimit -Sn user@host:~$ qgis To fix it forever On most Linux systems, resource limits are set on login by the pam_limits module according to the settings contained in /etc/security/limits.conf or /etc/security/limits.d/*.conf. You should be able to edit those files if you have root privilege (also via sudo), but you will need to log in again before any changes take effect. More info: http://www.cyberciti.biz/faq/linux-increase-the-maximum-number-of-open-files/ http://linuxaria.com/article/open- files-in-linux?lang=en . 12 Chapter 4. Features CHAPTER 5 What’s new in QGIS 2.6 This release contains new features and extends the programmatic interface over previous versions. We recommend that you use this version over previous releases. This release includes hundreds of bug fixes and many new features and enhancements that will be described in this manual. You may also review the visual changelog at http://changelog.linfiniti.com/qgis/version/2.6.0/. 5.1 Application and Project Options • Project filename in properties: You can now see the full path for the QGIS project file in the project properties dialog. 5.2 Data Providers • DXF Export tool improvements: – Tree view and attribute selection for layer assigment in dialog – support fill polygons/HATCH – represent texts as MTEXT instead of TEXT (including font, slant and weight) – support for RGB colors when there’s no exact color match – use AutoCAD 2000 DXF (R15) instead of R12 5.3 Map Composer • Update map canvas extent from map composer extent: On the Item properties of a Map element there are now two extra buttons which allow you to (1) set the Map canvas extent according with the extent of your Map element and (2) view in Map canvas the extent currently set on your Map element. • Multiple grid support: It is now possible to have more than one grid in your Map element. Each grid is fully customizable and can be assigned to a different CRS. This means, for example, you can now have a map layout with both geographic and projected grids. • Selective export: To every item of your map composer layout, under Rendering options, you may exclude that object from map exports. 13 QGIS User Guide, Release 2.6 5.4 QGIS Server 5.5 Symbology 5.6 User Interface . 14 Chapter 5. What’s new in QGIS 2.6 CHAPTER 6 Getting Started This chapter gives a quick overview of installing QGIS, some sample data from the QGIS web page, and running a first and simple session visualizing raster and vector layers. 6.1 Installation Installation of QGIS is very simple. Standard installer packages are available for MS Windows and Mac OS X. For many flavors of GNU/Linux, binary packages (rpm and deb) or software repositories are provided to add to your in- stallation manager. Get the latest information on binary packages at the QGIS website at http://download.qgis.org. 6.1.1 Installation from source If you need to build QGIS from source, please refer to the installation instructions. They are dis- tributed with the QGIS source code in a file called INSTALL. You can also find them online at http://htmlpreview.github.io/?https://raw.github.com/qgis/QGIS/master/doc/INSTALL.html 6.1.2 Installation on external media QGIS allows you to define a --configpath option that overrides the default path for user configuration (e.g., ~/.qgis2 under Linux) and forces QSettings to use this directory, too. This allows you to, for instance, carry a QGIS installation on a flash drive together with all plugins and settings. See section System Menu for additional information. 6.2 Sample Data The user guide contains examples based on the QGIS sample dataset. The Windows installer has an option to download the QGIS sample dataset. If checked, the data will be down- loaded to your My Documents folder and placed in a folder called GIS Database. You may use Windows Explorer to move this folder to any convenient location. If you did not select the checkbox to install the sample dataset during the initial QGIS installation, you may do one of the following: • Use GIS data that you already have • Download sample data from http://download.osgeo.org/qgis/data/qgis_sample_data.zip • Uninstall QGIS and reinstall with the data download option checked (only recommended if the above solu- tions are unsuccessful) For GNU/Linux and Mac OS X, there are not yet dataset installation packages available as rpm, deb or dmg. To use the sample dataset, download the file qgis_sample_data as a ZIP archive from http://download.osgeo.org/qgis/data/qgis_sample_data.zip and unzip the archive on your system. 15 QGIS User Guide, Release 2.6 The Alaska dataset includes all GIS data that are used for examples and screenshots in the user guide; it also includes a small GRASS database. The projection for the QGIS sample dataset is Alaska Albers Equal Area with units feet. The EPSG code is 2964. PROJCS["Albers Equal Area", GEOGCS["NAD27", DATUM["North_American_Datum_1927", SPHEROID["Clarke 1866",6378206.4,294.978698213898, AUTHORITY["EPSG","7008"]], TOWGS84[-3,142,183,0,0,0,0], AUTHORITY["EPSG","6267"]], PRIMEM["Greenwich",0, AUTHORITY["EPSG","8901"]], UNIT["degree",0.0174532925199433, AUTHORITY["EPSG","9108"]], AUTHORITY["EPSG","4267"]], PROJECTION["Albers_Conic_Equal_Area"], PARAMETER["standard_parallel_1",55], PARAMETER["standard_parallel_2",65], PARAMETER["latitude_of_center",50], PARAMETER["longitude_of_center",-154], PARAMETER["false_easting",0], PARAMETER["false_northing",0], UNIT["us_survey_feet",0.3048006096012192]] If you intend to use QGIS as a graphical front end for GRASS, you can find a selection of sample locations (e.g., Spearfish or South Dakota) at the official GRASS GIS website, http://grass.osgeo.org/download/sample-data/. 6.3 Sample Session Now that you have QGIS installed and a sample dataset available, we would like to demonstrate a short and simple QGIS sample session. We will visualize a raster and a vector layer. We will use the landcover raster layer, qgis_sample_data/raster/landcover.img, and the lakes vector layer, qgis_sample_data/gml/lakes.gml. 6.3.1 Start QGIS • Start QGIS by typing “QGIS” at a command prompt, or if using a precompiled binary, by using the Applications menu. • Start QGIS using the Start menu or desktop shortcut, or double click on a QGIS project file. • Double click the icon in your Applications folder. 6.3.2 Load raster and vector layers from the sample dataset 1. Click on the Load Raster icon. 2. Browse to the folder qgis_sample_data/raster/, select the ERDAS IMG file landcover.img and click [Open]. 3. If the file is not listed, check if the Files of type combo box at the bottom of the dialog is set on the right type, in this case “Erdas Imagine Images (*.img, *.IMG)”. 4. Now click on the Load Vector icon. 5. File should be selected as Source Type in the new Add vector layer dialog. Now click [Browse] to select the vector layer. 16 Chapter 6. Getting Started QGIS User Guide, Release 2.6 6. Browse to the folder qgis_sample_data/gml/, select ‘Geography Markup Language [GML] [OGR] (.gml,.GML)’ from the Files of type combo box, then select the GML file lakes.gml and click [Open]. In the Add vector layer dialog, click [OK]. The Coordinate Reference System Selector dialog opens with NAD27 / Alaska Alberts selected, click [OK]. 7. Zoom in a bit to your favorite area with some lakes. 8. Double click the lakes layer in the map legend to open the Properties dialog. 9. Click on the Style tab and select a blue as fill color. 10. Click on the Labels tab and check the Label this layer with checkbox to enable labeling. Choose the “NAMES” field as the field containing labels. 11. To improve readability of labels, you can add a white buffer around them by clicking “Buffer” in the list on the left, checking Draw text buffer and choosing 3 as buffer size. 12. Click [Apply]. Check if the result looks good, and finally click [OK]. You can see how easy it is to visualize raster and vector layers in QGIS. Let’s move on to the sections that follow to learn more about the available functionality, features and settings, and how to use them. 6.4 Starting and Stopping QGIS In section Sample Session you already learned how to start QGIS. We will repeat this here, and you will see that QGIS also provides further command line options. • Assuming that QGIS is installed in the PATH, you can start QGIS by typing qgis at a command prompt or by double clicking on the QGIS application link (or shortcut) on the desktop or in the Applications menu. • Start QGIS using the Start menu or desktop shortcut, or double click on a QGIS project file. • Double click the icon in your Applications folder. If you need to start QGIS in a shell, run /path-to-installation-executable/Contents/MacOS/Qgis. To stop QGIS, click the menu option File QGIS → Quit, or use the shortcut Ctrl+Q. 6.5 Command Line Options QGIS supports a number of options when started from the command line. To get a list of the options, enter qgis --help on the command line. The usage statement for QGIS is: qgis --help QGIS - 2.6.0-Brighton ’Brighton’ (exported) QGIS is a user friendly Open Source Geographic Information System. Usage: /usr/bin/qgis.bin [OPTION] [FILE] OPTION: [--snapshot filename] emit snapshot of loaded datasets to given file [--width width] width of snapshot to emit [--height height] height of snapshot to emit [--lang language] use language for interface text [--project projectfile] load the given QGIS project [--extent xmin,ymin,xmax,ymax] set initial map extent [--nologo] hide splash screen [--noplugins] don’t restore plugins on startup [--nocustomization] don’t apply GUI customization [--customizationfile] use the given ini file as GUI customization [--optionspath path] use the given QSettings path [--configpath path] use the given path for all user configuration [--code path] run the given python file on load 6.4. Starting and Stopping QGIS 17 QGIS User Guide, Release 2.6 [--defaultui] start by resetting user ui settings to default [--help] this text FILE: Files specified on the command line can include rasters, vectors, and QGIS project files (.qgs): 1. Rasters - supported formats include GeoTiff, DEM and others supported by GDAL 2. Vectors - supported formats include ESRI Shapefiles and others supported by OGR and PostgreSQL layers using the PostGIS extension Tip: Example Using command line arguments You can start QGIS by specifying one or more data files on the command line. For example, assuming you are in the qgis_sample_data directory, you could start QGIS with a vector layer and a raster file set to load on startup using the following command: qgis ./raster/landcover.img ./gml/lakes.gml Command line option --snapshot This option allows you to create a snapshot in PNG format from the current view. This comes in handy when you have a lot of projects and want to generate snapshots from your data. Currently, it generates a PNG file with 800x600 pixels. This can be adjusted using the --width and --height command line arguments. A filename can be added after --snapshot. Command line option --lang Based on your locale, QGIS selects the correct localization. If you would like to change your language, you can specify a language code. For example, --lang=it starts QGIS in italian localization. A list of currently supported languages with language code and status is provided at http://hub.qgis.org/wiki/quantum- gis/GUI_Translation_Progress. Command line option --project Starting QGIS with an existing project file is also possible. Just add the command line option --project followed by your project name and QGIS will open with all layers in the given file loaded. Command line option --extent To start with a specific map extent use this option. You need to add the bounding box of your extent in the following order separated by a comma: --extent xmin,ymin,xmax,ymax Command line option --nologo This command line argument hides the splash screen when you start QGIS. Command line option --noplugins If you have trouble at start-up with plugins, you can avoid loading them at start-up with this option. They will still be available from the Plugins Manager afterwards. Command line option --customizationfile Using this command line argument, you can define a GUI customization file, that will be used at startup. Command line option --nocustomization Using this command line argument, existing GUI customization will not be applied at startup. Command line option --optionspath You can have multiple configurations and decide which one to use when starting QGIS with this option. See Options to confirm where the operating system saves the settings files. Presently, there is no way to specify a file to write settings to; therefore, you can create a copy of the original settings file and rename it. The option specifies path to directory with settings. For example, to use /path/to/config/QGIS/QGIS2.ini settings file, use option: 18 Chapter 6. Getting Started QGIS User Guide, Release 2.6 --optionspath /path/to/config/ Command line option --configpath This option is similar to the one above, but furthermore overrides the default path for user configuration (~/.qgis2) and forces QSettings to use this directory, too. This allows users to, for instance, carry a QGIS installation on a flash drive together with all plugins and settings. Command line option --code This option can be used to run a given python file directly after QGIS has started. For example, when you have a python file named load_alaska.py with following content: from qgis.utils import iface raster_file="/home/gisadmin/Documents/qgis_sample_data/raster/landcover.img" layer_name="Alaska" iface.addRasterLayer(raster_file, layer_name) Assuming you are in the directory where the file load_alaska.py is located, you can start QGIS, load the raster file landcover.img and give the layer the name ‘Alaska’ using the following command: qgis --code load_alaska.py 6.6 Projects The state of your QGIS session is considered a project. QGIS works on one project at a time. Settings are considered as being either per-project or as a default for new projects (see section Options). QGIS can save the state of your workspace into a project file using the menu options Project → Save or Project → Save As.... Load saved projects into a QGIS session using Project → Open..., Project → New from template or Project → Open Recent →. If you wish to clear your session and start fresh, choose Project → New. Either of these menu options will prompt you to save the existing project if changes have been made since it was opened or last saved. The kinds of information saved in a project file include: • Layers added • Layer properties, including symbolization • Projection for the map view • Last viewed extent The project file is saved in XML format, so it is possible to edit the file outside QGIS if you know what you are doing. The file format has been updated several times compared with earlier QGIS versions. Project files from older QGIS versions may not work properly anymore. To be made aware of this, in the General tab under Settings → Options you can select: • Prompt to save project and data source changes when required • Warn when opening a project file saved with an older version of QGIS Whenever you save a project in QGIS 2.2 now a backup of the project file is made. 6.7 Output There are several ways to generate output from your QGIS session. We have discussed one already in section Projects, saving as a project file. Here is a sampling of other ways to produce output files: 6.6. Projects 19 QGIS User Guide, Release 2.6 • Menu option Project → Save as Image opens a file dialog where you select the name, path and type of image (PNG or JPG format). A world file with extension PNGW or JPGW saved in the same folder georeferences the image. • Menu option Project → DXF Export ... opens a dialog where you can define the ‘Symbology mode’, the ‘Symbology scale’ and vector layers you want to export to DXF. • Menu option Project → New Print Composer opens a dialog where you can lay out and print the current map canvas (see section Print Composer). . 20 Chapter 6. Getting Started CHAPTER 7 QGIS GUI When QGIS starts, you are presented with the GUI as shown in the figure (the numbers 1 through 5 in yellow circles are discussed below). Figure 7.1: QGIS GUI with Alaska sample data Note: Your window decorations (title bar, etc.) may appear different depending on your operating system and window manager. The QGIS GUI is divided into five areas: 1. Menu Bar 2. Tool Bar 3. Map Legend 4. Map View 5. Status Bar These five components of the QGIS interface are described in more detail in the following sections. Two more sections present keyboard shortcuts and context help. 21 QGIS User Guide, Release 2.6 7.1 Menu Bar The menu bar provides access to various QGIS features using a standard hierarchical menu. The top-level menus and a summary of some of the menu options are listed below, together with the associated icons as they appear on the toolbar, and keyboard shortcuts. The shortcuts presented in this section are the defaults; however, keyboard shortcuts can also be configured manually using the Configure shortcuts dialog, opened from Settings → Configure Shortcuts.... Although most menu options have a corresponding tool and vice-versa, the menus are not organized exactly like the toolbars. The toolbar containing the tool is listed after each menu option as a checkbox entry. Some menu options only appear if the corresponding plugin is loaded. For more information about tools and toolbars, see section Toolbar. 7.1.1 Project Menu Option Shortcut Reference Toolbar New Ctrl+N see Projects Project Open Ctrl+O see Projects Project New from template → see Projects Project Open Recent → see Projects Save Ctrl+S see Projects Project Save As... Ctrl+Shift+S see Projects Project Save as Image... see Output DXF Export ... see Output New Print Composer Ctrl+P see Print Composer Project Composer manager ... see Print Composer Project Print Composers → see Print Composer Exit QGIS Ctrl+Q 22 Chapter 7. QGIS GUI QGIS User Guide, Release 2.6 7.1.2 Edit Menu Option Shortcut Reference Toolbar Undo Ctrl+Z see Advanced digitizing Advanced Digitizing Redo Ctrl+Shift+Z see Advanced digitizing Advanced Digitizing Cut Features Ctrl+X see Digitizing an existing layer Digitizing Copy Features Ctrl+C see Digitizing an existing layer Digitizing Paste Features Ctrl+V see Digitizing an existing layer Digitizing Paste features as → see Working with the Attribute Table Add Feature Ctrl+. see Digitizing an existing layer Digitizing Move Feature(s) see Digitizing an existing layer Digitizing Delete Selected see Digitizing an existing layer Digitizing Rotate Feature(s) see Advanced digitizing Advanced Digitizing Simplify Feature see Advanced digitizing Advanced Digitizing Add Ring see Advanced digitizing Advanced Digitizing Add Part see Advanced digitizing Advanced Digitizing Fill Ring see Advanced digitizing Advanced Digitizing Delete Ring see Advanced digitizing Advanced Digitizing Delete Part see Advanced digitizing Advanced Digitizing Reshape Features see Advanced digitizing Advanced Digitizing Offset Curves see Advanced digitizing Advanced Digitizing Split Features see Advanced digitizing Advanced Digitizing Split Parts see Advanced digitizing Advanced Digitizing Merge Selected Features see Advanced digitizing Advanced Digitizing Merge Attr. of Selected Features see Advanced digitizing Advanced Digitizing Node Tool see Digitizing an existing layer Digitizing Rotate Point Symbols see Advanced digitizing Advanced Digitizing After activating Toggle editing mode for a layer, you will find the Add Feature icon in the Edit menu depend- ing on the layer type (point, line or polygon). 7.1.3 Edit (extra) Menu Option Shortcut Reference Toolbar Add Feature see Digitizing an existing layer Digitizing Add Feature see Digitizing an existing layer Digitizing Add Feature see Digitizing an existing layer Digitizing 7.1. Menu Bar 23 QGIS User Guide, Release 2.6 7.1.4 View Menu Option Shortcut Reference Toolbar Pan Map Map Navigation Pan Map to Selection Map Navigation Zoom In Ctrl++ Map Navigation Zoom Out Ctrl+- Map Navigation Select → see Select and deselect features Attributes Identify Features Ctrl+Shift+I Attributes Measure → see Measuring Attributes Zoom Full Ctrl+Shift+F Map Navigation Zoom To Layer Map Navigation Zoom To Selection Ctrl+J Map Navigation Zoom Last Map Navigation Zoom Next Map Navigation Zoom Actual Size Map Navigation Decorations → see Decorations Map Tips Attributes New Bookmark Ctrl+B see Spatial Bookmarks Attributes Show Bookmarks Ctrl+Shift+B see Spatial Bookmarks Attributes Refresh Ctrl+R Map Navigation 7.1.5 Layer Menu Option Shortcut Reference Toolbar New → see Creating new Vector layers Manage Layers Embed Layers and Groups ... see Nesting Projects Add Vector Layer Ctrl+Shift+V see Working with Vector Data Manage Layers Add Raster Layer Ctrl+Shift+R see Loading raster data in QGIS Manage Layers Add PostGIS Layer Ctrl+Shift+D see PostGIS Layers Manage Layers Add SpatiaLite Layer Ctrl+Shift+L see SpatiaLite Layers Manage Layers Add MSSQL Spatial Layer Ctrl+Shift+M see MSSQL Spatial Layers Manage Layers Add Oracle GeoRaster Layer see Oracle Spatial GeoRaster Plugin Manage Layers Add SQL Anywhere Layer see SQL Anywhere Plugin Manage Layers Add WMS/WMTS Layer Ctrl+Shift+W see WMS/WMTS Client Manage Layers Add WCS Layer see WCS Client Manage Layers Add WFS Layer see WFS and WFS-T Client Manage Layers Add Delimited Text Layer see Delimited Text Files Manage Layers Copy style see Style Menu Paste style see Style Menu Continued on next page 24 Chapter 7. QGIS GUI QGIS User Guide, Release 2.6 Table 7.1 – continued from previous page Menu Option Shortcut Reference Toolbar Open Attribute Table see Working with the Attribute Table Attributes Toggle Editing see Digitizing an existing layer Digitizing Save Layer Edits see Digitizing an existing layer Digitizing Current Edits → see Digitizing an existing layer Digitizing Save as... Save selection as vector file... See Working with the Attribute Table Remove Layer(s) Ctrl+D Duplicate Layers (s) Set CRS of Layer(s) Ctrl+Shift+C Set project CRS from Layer Properties Query... Labeling Add to Overview Ctrl+Shift+O Manage Layers Add All To Overview Remove All From Overview Show All Layers Ctrl+Shift+U Manage Layers Hide All Layers Ctrl+Shift+H Manage Layers 7.1.6 Settings Menu Option Shortcut Reference Toolbar Panels → see Panels and Toolbars Toolbars → see Panels and Toolbars Toggle Full Screen Mode F 11 Project Properties ... Ctrl+Shift+P see Projects Custom CRS ... see Custom Coordinate Reference System Style Manager... see Presentation Configure shortcuts ... Customization ... see Customization Options ... see Options Snapping Options ... 7.1.7 Plugins Menu Option Shortcut Reference Toolbar Manage and Install Plugins see The Plugins Dialog Python Console When starting QGIS for the first time not all core plugins are loaded. 7.1. Menu Bar 25 QGIS User Guide, Release 2.6 7.1.8 Vector Menu Option Shortcut Reference Toolbar Open Street Map → see Loading OpenStreetMap Vectors Analysis Tools → see fTools Plugin Research Tools → see fTools Plugin Geoprocessing Tools → see fTools Plugin Geometry Tools → see fTools Plugin Data Management Tools → see fTools Plugin When starting QGIS for the first time not all core plugins are loaded. 7.1.9 Raster Menu Option Shortcut Reference Toolbar Raster calculator ... see Raster Calculator When starting QGIS for the first time not all core plugins are loaded. 7.1.10 Processing Menu Option Shortcut Reference Toolbar Toolbox see The toolbox Graphical Modeler see The graphical modeler History and log see The history manager Options and configuration see Configuring the processing framework Results viewer see Configuring external applications Commander Ctrl+Alt+M see The QGIS Commander When starting QGIS for the first time not all core plugins are loaded. 7.1.11 Help Menu Option Shortcut Reference Toolbar Help Contents F1 Help What’s This? Shift+F1 Help API Documentation Need commercial support? QGIS Home Page Ctrl+H Check QGIS Version About QGIS Sponsors Please note that for Linux , the menu bar items listed above are the default ones in the KDE window manager. In GNOME, the Settings menu has different content and its items have to be found here: 26 Chapter 7. QGIS GUI QGIS User Guide, Release 2.6 Project Properties Project Options Edit Configure Shortcuts Edit Style Manager Edit Custom CRS Edit Panels → View Toolbars → View Toggle Full Screen Mode View Tile scale slider View Live GPS tracking View 7.2 Toolbar The toolbar provides access to most of the same functions as the menus, plus additional tools for interacting with the map. Each toolbar item has pop-up help available. Hold your mouse over the item and a short description of the tool’s purpose will be displayed. Every menu bar can be moved around according to your needs. Additionally, every menu bar can be switched off using your right mouse button context menu, holding the mouse over the toolbars (read also Panels and Toolbars). Tip: Restoring toolbars If you have accidentally hidden all your toolbars, you can get them back by choosing menu option Settings → Toolbars →. If a toolbar disappears under Windows, which seems to be a problem in QGIS from time to time, you have to remove key \HKEY_CURRENT_USER\Software\QGIS\qgis\UI\state in the registry. When you restart QGIS, the key is written again with the default state, and all toolbars are visible again. 7.3 Map Legend The map legend area lists all the layers in the project. The checkbox in each legend entry can be used to show or hide the layer. The Legend toolbar in the map legend are list allow you to Add group, Manage Layer Visibility of all layers or manage preset layers combination, Filter Legend by Map Content, Expand All or Collapse All and Remove Layer or Group. The button allows you to add Presets views in the legend. It means that you can choose to display some layer with specific categorization and add this view to the Presets list. To add a preset view just click on , choose Add Preset... from the drop down menu and give a name to the preset. After that you will see a list with all the presets that you can recall pressing on the button. All the added presets are also present in the map composer in order to allow you to create a map layout based on your specific views (see Main properties). A layer can be selected and dragged up or down in the legend to change the Z-ordering. Z-ordering means that layers listed nearer the top of the legend are drawn over layers listed lower down in the legend. Note: This behaviour can be overridden by the ‘Layer order’ panel. Layers in the legend window can be organised into groups. There are two ways to do this: 1. Press the icon to add a new group. Type in a name for the group and press Enter. Now click on an existing layer and drag it onto the group. 2. Select some layers, right click in the legend window and choose Group Selected. The selected layers will automatically be placed in a new group. 7.2. Toolbar 27 QGIS User Guide, Release 2.6 To bring a layer out of a group, you can drag it out, or right click on it and choose Make to toplevel item. Groups can also be nested inside other groups. The checkbox for a group will show or hide all the layers in the group with one click. The content of the right mouse button context menu depends on whether the selected legend item is a raster or a vector layer. For GRASS vector layers, Toggle editing is not available. See section Digitizing and editing a GRASS vector layer for information on editing GRASS vector layers. Right mouse button menu for raster layers • Zoom to layer extent • Show in overview • Zoom to Best Scale (100%) • Stretch Using Current Extent • Remove • Duplicate • Set Layer Scale Visibility • Set Layer CRS • Set Project CRS from Layer • Save as ... • Save As Layer Definition Style • Properties • Rename • Copy Style Additionally, according to layer position and selection • Make to toplevel item • Group Selected Right mouse button menu for vector layers • Zoom to Layer Extent • Show in Overview • Remove • Duplicate • Set Layer Scale Visibility • Set Layer CRS • Set Project CRS from Layer • Open Attribute Table • Toggle Editing (not available for GRASS layers) • Save As ... • Save As Layer Definition Style • Filter • Show Feature Count • Properties • Rename 28 Chapter 7. QGIS GUI QGIS User Guide, Release 2.6 • Copy Style Additionally, according to layer position and selection • Make to toplevel item • Group Selected Right mouse button menu for layer groups • Zoom to Group • Remove • Set Group CRS • Rename • Add Group It is possible to select more than one layer or group at the same time by holding down the Ctrl key while selecting the layers with the left mouse button. You can then move all selected layers to a new group at the same time. You may also delete more than one layer or group at once by selecting several layers with the Ctrl key and pressing Ctrl+D afterwards. This way, all selected layers or groups will be removed from the layers list. 7.3.1 Working with the Legend independent layer order There is a panel that allows you to define an independent drawing order for the map legend. You can activate it in the menu Settings → Panels → Layer order. This feature allows you to, for instance, order your layers in order of importance, but still display them in the correct order (see figure_layer_order). Checking the Control rendering order box underneath the list of layers will cause a revert to default behavior. Figure 7.2: Define a legend independent layer order 7.3. Map Legend 29 QGIS User Guide, Release 2.6 7.4 Map View This is the “business end” of QGIS — maps are displayed in this area! The map displayed in this window will depend on the vector and raster layers you have chosen to load (see sections that follow for more information on how to load layers). The map view can be panned, shifting the focus of the map display to another region, and it can be zoomed in and out. Various other operations can be performed on the map as described in the toolbar description above. The map view and the legend are tightly bound to each other — the maps in view reflect changes you make in the legend area. Tip: Zooming the Map with the Mouse Wheel You can use the mouse wheel to zoom in and out on the map. Place the mouse cursor inside the map area and roll the wheel forward (away from you) to zoom in and backwards (towards you) to zoom out. The zoom is centered on the mouse cursor position. You can customize the behavior of the mouse wheel zoom using the Map tools tab under the Settings → Options menu. Tip: Panning the Map with the Arrow Keys and Space Bar You can use the arrow keys to pan the map. Place the mouse cursor inside the map area and click on the right arrow key to pan east, left arrow key to pan west, up arrow key to pan north and down arrow key to pan south. You can also pan the map using the space bar or the click on mouse wheel: just move the mouse while holding down space bar or click on mouse wheel. 7.5 Status Bar The status bar shows you your current position in map coordinates (e.g., meters or decimal degrees) as the mouse pointer is moved across the map view. To the left of the coordinate display in the status bar is a small button that will toggle between showing coordinate position or the view extents of the map view as you pan and zoom in and out. Next to the coordinate display you will find the scale display. It shows the scale of the map view. If you zoom in or out, QGIS shows you the current scale. There is a scale selector, which allows you to choose between predefined scales from 1:500 to 1:1000000. A progress bar in the status bar shows the progress of rendering as each layer is drawn to the map view. In some cases, such as the gathering of statistics in raster layers, the progress bar will be used to show the status of lengthy operations. If a new plugin or a plugin update is available, you will see a message at the far left of the status bar. On the right side of the status bar, there is a small checkbox which can be used to temporarily prevent layers being rendered to the map view (see section Rendering below). The icon immediately stops the current map rendering process. To the right of the render functions, you find the EPSG code of the current project CRS and a projector icon. Clicking on this opens the projection properties for the current project. Tip: Calculating the Correct Scale of Your Map Canvas When you start QGIS, the default units are degrees, and this means that QGIS will interpret any coordinate in your layer as specified in degrees. To get correct scale values, you can either change this setting to meters manually in the General tab under Settings → Project Properties, or you can select a project CRS clicking on the CRS status icon in the lower right-hand corner of the status bar. In the last case, the units are set to what the project projection specifies (e.g., ‘+units=m’). . 30 Chapter 7. QGIS GUI CHAPTER 8 General Tools 8.1 Keyboard shortcuts QGIS provides default keyboard shortcuts for many features. You can find them in section Menu Bar. Addition- ally, the menu option Settings → Configure Shortcuts.. allows you to change the default keyboard shortcuts and to add new keyboard shortcuts to QGIS features. Figure 8.1: Define shortcut options (Gnome) Configuration is very simple. Just select a feature from the list and click on [Change],[Set none] or [Set default]. Once you have finished your configuration, you can save it as an XML file and load it to another QGIS installation. 8.2 Context help When you need help on a specific topic, you can access context help via the [Help] button available in most dialogs — please note that third-party plugins can point to dedicated web pages. 8.3 Rendering By default, QGIS renders all visible layers whenever the map canvas is refreshed. The events that trigger a refresh of the map canvas include: • Adding a layer • Panning or zooming 31 QGIS User Guide, Release 2.6 • Resizing the QGIS window • Changing the visibility of a layer or layers QGIS allows you to control the rendering process in a number of ways. 8.3.1 Scale Dependent Rendering Scale-dependent rendering allows you to specify the minimum and maximum scales at which a layer will be visible. To set scale-dependent rendering, open the Properties dialog by double-clicking on the layer in the legend. On the General tab, click on the Scale dependent visibility checkbox to activate the feature, then set the minimum and maximum scale values. You can determine the scale values by first zooming to the level you want to use and noting the scale value in the QGIS status bar. 8.3.2 Controlling Map Rendering Map rendering can be controlled in the various ways, as described below. Suspending Rendering To suspend rendering, click the Render checkbox in the lower right corner of the status bar. When the Render checkbox is not checked, QGIS does not redraw the canvas in response to any of the events described in section Rendering. Examples of when you might want to suspend rendering include: • Adding many layers and symbolizing them prior to drawing • Adding one or more large layers and setting scale dependency before drawing • Adding one or more large layers and zooming to a specific view before drawing • Any combination of the above Checking the Render checkbox enables rendering and causes an immediate refresh of the map canvas. Setting Layer Add Option You can set an option to always load new layers without drawing them. This means the layer will be added to the map, but its visibility checkbox in the legend will be unchecked by default. To set this option, choose menu option Settings → Options and click on the Rendering tab. Uncheck the By default new layers added to the map should be displayed checkbox. Any layer subsequently added to the map will be off (invisible) by default. Stopping Rendering To stop the map drawing, press the ESC key. This will halt the refresh of the map canvas and leave the map partially drawn. It may take a bit of time between pressing ESC and the time the map drawing is halted. Note: It is currently not possible to stop rendering — this was disabled in the Qt4 port because of User Interface (UI) problems and crashes. 32 Chapter 8. General Tools QGIS User Guide, Release 2.6 Updating the Map Display During Rendering You can set an option to update the map display as features are drawn. By default, QGIS does not display any features for a layer until the entire layer has been rendered. To update the display as features are read from the datastore, choose menu option Settings → Options and click on the Rendering tab. Set the feature count to an appropriate value to update the display during rendering. Setting a value of 0 disables update during drawing (this is the default). Setting a value too low will result in poor performance, as the map canvas is continually updated during the reading of the features. A suggested value to start with is 500. Influence Rendering Quality To influence the rendering quality of the map, you have two options. Choose menu option Settings → Options, click on the Rendering tab and select or deselect following checkboxes: • Make lines appear less jagged at the expense of some drawing performance • Fix problems with incorrectly filled polygons Speed-up rendering There are two settings that allow you to improve rendering speed. Open the QGIS options dialog using Settings → Options, go to the Rendering tab and select or deselect the following checkboxes: • Enable back buffer. This provides better graphics performance at the cost of losing the possibility to cancel rendering and incrementally draw features. If it is unchecked, you can set the Number of features to draw before updating the display, otherwise this option is inactive. • Use render caching where possible to speed up redraws 8.4 Measuring Measuring works within projected coordinate systems (e.g., UTM) and unprojected data. If the loaded map is defined with a geographic coordinate system (latitude/longitude), the results from line or area measurements will be incorrect. To fix this, you need to set an appropriate map coordinate system (see section Working with Projections). All measuring modules also use the snapping settings from the digitizing module. This is useful, if you want to measure along lines or areas in vector layers. To select a measuring tool, click on and select the tool you want to use. 8.4.1 Measure length, areas and angles Measure Line: QGIS is able to measure real distances between given points according to a defined ellipsoid. To configure this, choose menu option Settings → Options, click on the Map tools tab and select the appropriate ellipsoid. There, you can also define a rubberband color and your preferred measurement units (meters or feet) and angle units (degrees, radians and gon). The tool then allows you to click points on the map. Each segment length, as well as the total, shows up in the measure window. To stop measuring, click your right mouse button. Measure Area: Areas can also be measured. In the measure window, the accumulated area size appears. In addition, the measuring tool will snap to the currently selected layer, provided that layer has its snapping tolerance set (see section Setting the Snapping Tolerance and Search Radius). So, if you want to measure exactly along a line feature, or around a polygon feature, first set its snapping tolerance, then select the layer. Now, when using the measuring tools, each mouse click (within the tolerance setting) will snap to that layer. 8.4. Measuring 33 QGIS User Guide, Release 2.6 Figure 8.2: Measure Distance (Gnome) Figure 8.3: Measure Area (Gnome) Measure Angle: You can also measure angles. The cursor becomes cross-shaped. Click to draw the first segment of the angle you wish to measure, then move the cursor to draw the desired angle. The measure is displayed in a pop-up dialog. Figure 8.4: Measure Angle (Gnome) 8.4.2 Select and deselect features The QGIS toolbar provides several tools to select features in the map canvas. To select one or several features, just click on and select your tool: • Select Single Feature • Select Features by Rectangle • Select Features by Polygon • Select Features by Freehand • Select Features by Radius To deselect all selected features click on Deselect features from all layers. Select feature using an expression allow user to select feature using expression dialog. See Expressions chapter for some example. Users can save features selection into a New Memory Vector Layer or a New Vector Layer using Edit → Paste Feature as ... and choose the mode you want. 34 Chapter 8. General Tools QGIS User Guide, Release 2.6 8.5 Identify features The Identify tool allows you to interact with the map canvas and get information on features in a pop-up window. To identify features, use View → Identify features or press Ctrl + Shift + I, or click on the Identify features icon in the toolbar. If you click on several features, the Identify results dialog will list information about all the selected features. The first item is the number of the feature in the list of results, followed by the layer name. Then, its first child will be the name of a field with its value. Finally, all information about the feature is displayed. This window can be customized to display custom fields, but by default it will display three kinds of information: • Actions: Actions can be added to the identify feature windows. When clicking on the action label, action will be run. By default, only one action is added, to view feature form for editing. • Derived: This information is calculated or derived from other information. You can find clicked coordinate, X and Y coordinates, area in map units and perimeter in map units for polygons, length in map units for lines and feature ids. • Data attributes: This is the list of attribute fields from the data. Figure 8.5: Identify feaures dialog (Gnome) At the bottom of the window, you have five icons: • Expand tree • Collapse tree • Default behaviour • Copy attributes • Print selected HTML response Other functions can be found in the context menu of the identified item. For example, from the context menu you can: • View the feature form • Zoom to feature • Copy feature: Copy all feature geometry and attributes • Toggle feature selection: adds identified feature to selection • Copy attribute value: Copy only the value of the attribute that you click on 8.5. Identify features 35 QGIS User Guide, Release 2.6 • Copy feature attributes: Copy only attributes • Clear result: Remove results in the window • Clear highlights: Remove features highlighted on the map • Highlight all • Highlight layer • Activate layer: Choose a layer to be activated • Layer properties: Open layer properties window • Expand all • Collapse all 8.6 Decorations The Decorations of QGIS include the Grid, the Copyright Label, the North Arrow and the Scale Bar. They are used to ‘decorate’ the map by adding cartographic elements. 8.6.1 Grid Grid allows you to add a coordinate grid and coordinate annotations to the map canvas. Figure 8.6: The Grid Dialog 1. Select from menu View → Decorations → Grid. The dialog starts (see figure_decorations_1). 2. Activate the Enable grid checkbox and set grid definitions according to the layers loaded in the map canvas. 3. Activate the Draw annotations checkbox and set annotation definitions according to the layers loaded in the map canvas. 4. Click [Apply] to verify that it looks as expected. 5. Click [OK] to close the dialog. 36 Chapter 8. General Tools QGIS User Guide, Release 2.6 8.6.2 Copyright Label Copyright label adds a copyright label using the text you prefer to the map. Figure 8.7: The Copyright Dialog 1. Select from menu View → Decorations → Copyright Label. The dialog starts (see figure_decorations_2). 2. Enter the text you want to place on the map. You can use HTML as shown in the example. 3. Choose the placement of the label from the Placement combo box. 4. Make sure the Enable Copyright Label checkbox is checked. 5. Click [OK]. In the example above, which is the default, QGIS places a copyright symbol followed by the date in the lower right-hand corner of the map canvas. 8.6.3 North Arrow North Arrow places a simple north arrow on the map canvas. At present, there is only one style available. You can adjust the angle of the arrow or let QGIS set the direction automatically. If you choose to let QGIS determine the direction, it makes its best guess as to how the arrow should be oriented. For placement of the arrow, you have four options, corresponding to the four corners of the map canvas. Figure 8.8: The North Arrow Dialog 8.6. Decorations 37 QGIS User Guide, Release 2.6 8.6.4 Scale Bar Scale Bar adds a simple scale bar to the map canvas. You can control the style and placement, as well as the labeling of the bar. Figure 8.9: The Scale Bar Dialog QGIS only supports displaying the scale in the same units as your map frame. So if the units of your layers are in meters, you can’t create a scale bar in feet. Likewise, if you are using decimal degrees, you can’t create a scale bar to display distance in meters. To add a scale bar: 1. Select from menu View → Decorations → Scale Bar. The dialog starts (see figure_decorations_4). 2. Choose the placement from the Placement combo box. 3. Choose the style from the Scale bar style combo box. 4. Select the color for the bar Color of bar or use the default black color. 5. Set the size of the bar and its label Size of bar . 6. Make sure the Enable scale bar checkbox is checked. 7. Optionally, check Automatically snap to round number on resize. 8. Click [OK]. Tip: Settings of Decorations When you save a .qgs project, any changes you have made to Grid, North Arrow, Scale Bar and Copyright will be saved in the project and restored the next time you load the project. 8.7 Annotation Tools The Text Annotation tool in the attribute toolbar provides the possibility to place formatted text in a balloon on the QGIS map canvas. Use the Text Annotation tool and click into the map canvas. Double clicking on the item opens a dialog with various options. There is the text editor to enter the formatted text and other item settings. For instance, there is the choice of having the item placed on a map position (displayed by a marker symbol) or to have the item on a screen position (not related to the map). The item can be moved by map position (by dragging the map marker) or by moving only the balloon. The icons are part of the GIS theme, and they are used by default in the other themes, too. 38 Chapter 8. General Tools QGIS User Guide, Release 2.6 Figure 8.10: Annotation text dialog The Move Annotation tool allows you to move the annotation on the map canvas. 8.7.1 Html annotations The Html Annotation tools in the attribute toolbar provides the possibility to place the content of an html file in a balloon on the QGIS map canvas. Using the Html Annotation tool, click into the map canvas and add the path to the html file into the dialog. 8.7.2 SVG annotations The SVG Annotation tool in the attribute toolbar provides the possibility to place an SVG symbol in a balloon on the QGIS map canvas. Using the SVG Annotation tool, click into the map canvas and add the path to the SVG file into the dialog. 8.7.3 Form annotations Additionally, you can also create your own annotation forms. The Form Annotation tool is useful to display attributes of a vector layer in a customized Qt Designer form (see figure_custom_annotation). This is similar to the designer forms for the Identify features tool, but displayed in an annotation item. Also see this video https://www.youtube.com/watch?v=0pDBuSbQ02o from Tim Sutton for more information. Note: If you press Ctrl+T while an Annotation tool is active (move annotation, text annotation, form annota- tion), the visibility states of the items are inverted. 8.8 Spatial Bookmarks Spatial Bookmarks allow you to “bookmark” a geographic location and return to it later. 8.8. Spatial Bookmarks 39 QGIS User Guide, Release 2.6 Figure 8.11: Customized qt designer annotation form 8.8.1 Creating a Bookmark To create a bookmark: 1. Zoom or pan to the area of interest. 2. Select the menu option View → New Bookmark or press Ctrl-B. 3. Enter a descriptive name for the bookmark (up to 255 characters). 4. Press Enter to add the bookmark or [Delete] to remove the bookmark. Note that you can have multiple bookmarks with the same name. 8.8.2 Working with Bookmarks To use or manage bookmarks, select the menu option View → Show Bookmarks. The Geospatial Bookmarks dialog allows you to zoom to or delete a bookmark. You cannot edit the bookmark name or coordinates. 8.8.3 Zooming to a Bookmark From the Geospatial Bookmarks dialog, select the desired bookmark by clicking on it, then click [Zoom To]. You can also zoom to a bookmark by double-clicking on it. 8.8.4 Deleting a Bookmark To delete a bookmark from the Geospatial Bookmarks dialog, click on it, then click [Delete]. Confirm your choice by clicking [Yes], or cancel the delete by clicking [No]. 40 Chapter 8. General Tools QGIS User Guide, Release 2.6 8.9 Nesting Projects If you want to embed content from other project files into your project, you can choose Layer → Embed Layers and Groups. 8.9.1 Embedding layers The following dialog allows you to embed layers from other projects. Here is a small example: 1. Press to look for another project from the Alaska dataset. 2. Select the project file grassland. You can see the content of the project (see figure_embed_dialog). 3. Press Ctrl and click on the layers grassland and regions. Press [OK]. The selected layers are embedded in the map legend and the map view now. Figure 8.12: Select layers and groups to embed While the embedded layers are editable, you can’t change their properties like style and labeling. 8.9.2 Removing embedded layers Right-click on the embedded layer and choose Remove. . 8.9. Nesting Projects 41 QGIS User Guide, Release 2.6 42 Chapter 8. General Tools CHAPTER 9 QGIS Configuration QGIS is highly configurable through the Settings menu. Choose between Panels, Toolbars, Project Properties, Options and Customization. Note: QGIS follows desktop guidelines for the location of options and project properties item. Consequently related to the OS you are using, location of some of items described above could be located in the :menuselec- tion‘view‘ menu (Panels and Toolbars) or in Project for Options. 9.1 Panels and Toolbars In the Panels→ menu, you can switch on and off QGIS widgets. The Toolbars→ menu provides the possibility to switch on and off icon groups in the QGIS toolbar (see figure_panels_toolbars). Figure 9.1: The Panels and Toolbars menu Tip: Activating the QGIS Overview 43 QGIS User Guide, Release 2.6 In QGIS, you can use an overview panel that provides a full extent view of layers added to it. It can be selected under the menu Settings → Panels or View → Panels. Within the view is a rectangle showing the current map extent. This allows you to quickly determine which area of the map you are currently viewing. Note that labels are not rendered to the map overview even if the layers in the map overview have been set up for labeling. If you click and drag the red rectangle in the overview that shows your current extent, the main map view will update accordingly. Tip: Show Log Messages It’s possible to track the QGIS messages. You can activate Log Messages in the menu Settings → Panels or View → Panels and follow the messages that appear in the different tabs during loading and operation. 9.2 Project Properties In the properties window for the project under Settings → Project Properties (kde) or Project → Project Properties (Gnome), you can set project-specific options. These include: • In the General menu, the project title, selection and background color, layer units, precision, and the option to save relative paths to layers can be defined. If the CRS transformation is on, you can choose an ellipsoid for distance calculations. You can define the canvas units (only used when CRS transformation is disabled) and the precision of decimal places to use. You can also define a project scale list, which overrides the global predefined scales. • The CRS menu enables you to choose the Coordinate Reference System for this project, and to enable on-the-fly re-projection of raster and vector layers when displaying layers from a different CRS. • With the third Identify layers menu, you set (or disable) which layers will respond to the identify tool (see the “Map tools” paragraph from the Options section to enable identifying of multiple layers). • The Default Styles menu lets you control how new layers will be drawn when they do not have an existing .qml style defined. You can also set the default transparency level for new layers and whether symbols should have random colours assigned to them. There is also an additional section where you can define specific colors for the running project. You can find the added colors in the drop down menu of the color dialog window present in each renderer. • The tab OWS Server allows you to define information about the QGIS Server WMS and WFS capabilities, extent and CRS restrictions. • The Macros menu is used to edit Python macros for projects. Currently, only three macros are available: openProject(), saveProject() and closeProject(). • The Relations menu is used to define 1:n relations. The relations are defined in the project properties dialog. Once relations exist for a layer, a new user interface element in the form view (e.g. when identifying a feature and opening its form) will list the related entities. This provides a powerful way to express e.g. the inspection history on a length of pipeline or road segment. You can find out more about 1:n relations support in Section Creating one to many relations. 9.3 Options Some basic options for QGIS can be selected using the Options dialog. Select the menu option Settings → Options. The tabs where you can customize your options are described below. 9.3.1 General Menu Application 44 Chapter 9. QGIS Configuration QGIS User Guide, Release 2.6 Figure 9.2: Macro settings in QGIS • Select the Style (QGIS restart required) and choose between ‘Oxygen’,’Windows’,’Motif’,’CDE’, ‘Plastique’ and ‘Cleanlooks’ ( ). • Define the Icon theme . Currently only ‘default’ is possible. • Define the Icon size . • Define the Font. Choose between Qt default and a user-defined font. • Change the Timeout for timed messages or dialogs . • Hide splash screen at startup • Show tips at startup • Bold group box titles • QGIS-styled group boxes • Use live-updating color chooser dialog Project files • Open project on launch (choose between ‘New’, ‘Most recent’ and ‘Specific’). When choosing ‘Specific’ use the to define a project. • Create new project from default project. You have the possibility to press on Set current project as default or on Reset default. You can browse through your files and define a directory where you find your user-defined project templates. This will be added to Project → New From Template. If you first activate Create new project from default project and then save a project in the project templates folder. • Prompt to save project and data source changes when required • Warn when opening a project file saved with an older version of QGIS • Enable macros . This option was created to handle macros that are written to perform an action on project events. You can choose between ‘Never’, ‘Ask’, ‘For this session only’ and ‘Always (not recom- mended)’. 9.3. Options 45 QGIS User Guide, Release 2.6 9.3.2 System Menu Environment System environment variables can now be viewed, and many configured, in the Environment group (see fig- ure_environment_variables). This is useful for platforms, such as Mac, where a GUI application does not nec- essarily inherit the user’s shell environment. It’s also useful for setting and viewing environment variables for the external tool sets controlled by the Processing toolbox (e.g., SAGA, GRASS), and for turning on debugging output for specific sections of the source code. • Use custom variables (restart required - include separators). You can [Add] and [Remove] variables. Already-defined environment variables are displayed in Current environment variables, and it’s possible to filter them by activating Show only QGIS-specific variables. Figure 9.3: System environment variables in QGIS Plugin paths [Add] or [Remove] Path(s) to search for additional C++ plugin libraries 9.3.3 Data Sources Menu Feature attributes and table • Open attribute table in a dock window (QGIS restart required) • Copy geometry in WKT representation from attribute table. When using Copy selected rows to clipboard from the Attribute table dialog, this has the result that the coordinates of points or vertices are also copied to the clipboard. • Attribute table behaviour . There are three possibilities: ‘Show all features’, ‘Show selected features’ and ‘Show features visible on map’. 46 Chapter 9. QGIS Configuration QGIS User Guide, Release 2.6 • Attribute table row cache . This row cache makes it possible to save the last loaded N attribute rows so that working with the attribute table will be quicker. The cache will be deleted when closing the attribute table. • Representation for NULL values. Here, you can define a value for data fields containing a NULL value. Data source handling • Scan for valid items in the browser dock . You can choose between ‘Check extension’ and ‘Check file contents’. • Scan for contents of compressed files (.zip) in browser dock . ‘No’, ‘Basic scan’ and ‘Full scan’ are possible. • Prompt for raster sublayers when opening. Some rasters support sublayers — they are called subdatasets in GDAL. An example is netCDF files — if there are many netCDF variables, GDAL sees every variable as a subdataset. The option allows you to control how to deal with sublayers when a file with sublayers is opened. You have the following choices: –‘Always’: Always ask (if there are existing sublayers) –‘If needed’: Ask if layer has no bands, but has sublayers –‘Never’: Never prompt, will not load anything –‘Load all’: Never prompt, but load all sublayers • Ignore shapefile encoding declaration. If a shapefile has encoding information, this will be ignored by QGIS. • Add PostGIS layer with double click and select in extended mode • Add Oracle layers with double click and select in extended mode 9.3.4 Rendering Menu Rendering behaviour • By default new layers added to the map should be displayed • Use render caching where possible to speed up redraws • Render layers in parallel using many CPU cores • Max cores to use • Map update interval (default to 250 ms) • Enable feature simplication by default for newly added layers • Simplification threshold • Simplify on provider side if possible • Maximum scale at which the layer should be simplified Rendering quality • Make lines appear less jagged at the expense of some drawing performance Rasters • With RGB band selection, you can define the number for the Red, Green and Blue band. Contrast enhancement 9.3. Options 47 QGIS User Guide, Release 2.6 • Single band gray . A single band gray can have ‘No stretch’, ‘Stretch to MinMax’, ‘Stretch and Clip to MinMax’ and also ‘Clip to MinMax’. • Multi band color (byte/band) . Options are ‘No stretch’, ‘Stretch to MinMax’, ‘Stretch and Clip to MinMax’ and ‘Clip to MinMax’. • Multi band color (>byte/band) . Options are ‘No stretch’, ‘Stretch to MinMax’, ‘Stretch and Clip to MinMax’ and ‘Clip to MinMax’. • Limits (minimum/maximum) . Options are ‘Cumulative pixel count cut’, ‘Minimum/Maximum’, ‘Mean +/- standard deviation’. • Cumulative pixel count cut limits • Standard deviation multiplier Debugging • Map canvas refresh 9.3.5 Colors Menu This menu allows you to add some custom color that you can find in each color dialog window of the renderes. You will see a set of predefined colors in the tab: you can delete or edit all of them. Moreover you can add the color you want and perform some copy and paste operation. Finally you can export the color set as a gpl file or import them. 9.3.6 Canvas and Legend Menu Default map appearance (overridden by project properties) • Define a Selection color and a Background color. Layer legend • Double click action in legend . You can either ‘Open layer properties’ or ‘Open attribute table’ with the double click. • The following Legend item styles are possible: – Capitalise layer names – Bold layer names – Bold group names – Display classification attribute names – Create raster icons (may be slow) – Add new layers to selected or current group 9.3.7 Map tools Menu This menu offers some options regarding the behaviour of the Identify tool. • Search radius for identifying and displaying map tips is a tolerance factor expressed as a percentage of the map width. This means the identify tool will depict results as long as you click within this tolerance. • Highlight color allows you to choose with which color should features being identified are to be highlighted. 48 Chapter 9. QGIS Configuration QGIS User Guide, Release 2.6 • Buffer expressed as a percentage of the map width, determines a buffer distance to be rendered from the outline of the identify highlight. • Minimum width expressed as a percentage of the map width, determines how thick should the outline of a highlighted object be. Measure tool • Define Rubberband color for measure tools • Define Decimal places • Keep base unit • Preferred measurements units (‘Meters’, ‘Feet’, ‘Nautical Miles’ or ‘Degrees’)‘ • Preferred angle units (‘Degrees’, ‘Radians’ or ‘Gon’) Panning and zooming • Define Mouse wheel action (‘Zoom’, ‘Zoom and recenter’, ‘Zoom to mouse cursor’, ‘Nothing’) • Define Zoom factor for wheel mouse Predefined scales Here, you find a list of predefined scales. With the [+] and [-] buttons you can add or remove your individual scales. 9.3.8 Composer Menu Composition defaults You can define the Default font here. Grid appearance • Define the Grid style (‘Solid’, ‘Dots’, ‘Crosses’) • Define the Color... Grid defaults • Define the Spacing • Define the Grid offset for x and y • Define the Snap tolerance Guide defaults • Define the Snap tolerance 9.3.9 Digitizing Menu Feature creation • Suppress attributes pop-up windows after each created feature • Reuse last entered attribute values • Validate geometries. Editing complex lines and polygons with many nodes can result in very slow rendering. This is because the default validation procedures in QGIS can take a lot of time. To speed up rendering, it is possible to select GEOS geometry validation (starting from GEOS 3.3) or to switch it off. GEOS geometry validation is much faster, but the disadvantage is that only the first geometry problem will be reported. Rubberband 9.3. Options 49 QGIS User Guide, Release 2.6 • Define Rubberband Line width and Line color Snapping • Open snapping options in a dock window (QGIS restart required) • Define Default snap mode (‘To vertex’, ‘To segment’, ‘To vertex and segment’, ‘Off’) • Define Default snapping tolerance in map units or pixels • Define the Search radius for vertex edits in map units or pixels Vertex markers • Show markers only for selected features • Define vertex Marker style (‘Cross’ (default), ‘Semi transparent circle’ or ‘None’) • Define vertex Marker size Curve offset tool The next 3 options refer to the Offset Curve tool in Advanced digitizing. Through the various settings, it is possible to influence the shape of the line offset. These options are possible starting from GEOS 3.3. • Join style • Quadrant segments • Miter limit 9.3.10 GDAL Menu GDAL is a data exchange library for raster files. In this tab, you can Edit create options and Edit Pyramids Options of the raster formats. Define which GDAL driver is to be used for a raster format, as in some cases more than one GDAL driver is available. 9.3.11 CRS Menu Default CRS for new projects • Don’t enable ‘on the fly’ reprojection • Automatically enable ‘on the fly’ reprojection if layers have different CRS • Enable ‘on the fly’ reprojection by default • Select a CRS and Always start new projects with this CRS CRS for new layers This area allows you to define the action to take when a new layer is created, or when a layer without a CRS is loaded. • Prompt for CRS • Use project CRS • Use default CRS displayed below Default datum transformations • Ask for datum transformation when no default is defined • If you have worked with the ‘on-the-fly’ CRS transformation you can see the result of the transformation in the window below. You can find information about ‘Source CRS’ and ‘Destination CRS’ as well as ‘Source datum transform’ and ‘Destination datum transform’. 50 Chapter 9. QGIS Configuration QGIS User Guide, Release 2.6 9.3.12 Locale Menu • Overwrite system locale and Locale to use instead • Information about active system locale 9.3.13 Network Menu General • Define WMS search address, default is http://geopole.org/wms/search?search=\%1\&type=rss • Define Timeout for network requests (ms) - default is 60000 • Define Default expiration period for WMSC/WMTS tiles (hours) - default is 24 • Define Max retry in case of tile request errors • Define User-Agent Figure 9.4: Proxy-settings in QGIS Cache settings Define the Directory and a Size for the cache. 9.3. Options 51 QGIS User Guide, Release 2.6 • Use proxy for web access and define ‘Host’, ‘Port’, ‘User’, and ‘Password’. • Set the Proxy type according to your needs. – Default Proxy: Proxy is determined based on the application proxy set using – Socks5Proxy: Generic proxy for any kind of connection. Supports TCP, UDP, binding to a port (in- coming connections) and authentication. – HttpProxy: Implemented using the “CONNECT” command, supports only outgoing TCP connections; supports authentication. – HttpCachingProxy: Implemented using normal HTTP commands, it is useful only in the context of HTTP requests. – FtpCachingProxy: Implemented using an FTP proxy, it is useful only in the context of FTP requests. Excluding some URLs can be added to the text box below the proxy settings (see Figure_Network_Tab). If you need more detailed information about the different proxy settings, please refer to the manual of the under- lying QT library documentation at http://doc.trolltech.com/4.5/qnetworkproxy.html#ProxyType-enum. Tip: Using Proxies Using proxies can sometimes be tricky. It is useful to proceed by ‘trial and error’ with the above proxy types, to check to see if they succeed in your case. You can modify the options according to your needs. Some of the changes may require a restart of QGIS before they will be effective. • Settings are saved in a text file: $HOME/.config/QGIS/QGIS2.conf • You can find your settings in: $HOME/Library/Preferences/org.qgis.qgis.plist • Settings are stored in the registry under: HKEY\CURRENT_USER\Software\QGIS\qgis 9.4 Customization The customization tool lets you (de)activate almost every element in the QGIS user interface. This can be very useful if you have a lot of plugins installed that you never use and that are filling your screen. Figure 9.5: The Customization dialog QGIS Customization is divided into five groups. In Menus, you can hide entries in the Menu bar. In Panel, you find the panel windows. Panel windows are applications that can be started and used as a floating, top-level window or embedded to the QGIS main window as a docked widget (see also Panels and Toolbars). In the 52 Chapter 9. QGIS Configuration QGIS User Guide, Release 2.6 Status Bar, features like the coordinate information can be deactivated. In Toolbars, you can (de)activate the toolbar icons of QGIS, and in Widgets, you can (de)activate dialogs as well as their buttons. With Switch to catching widgets in main application, you can click on elements in QGIS that you want to be hidden and find the corresponding entry in Customization (see figure_customization). You can also save your various setups for different use cases as well. Before your changes are applied, you need to restart QGIS. . 9.4. Customization 53 QGIS User Guide, Release 2.6 54 Chapter 9. QGIS Configuration CHAPTER 10 Working with Projections QGIS allows users to define a global and project-wide CRS (coordinate reference system) for layers without a pre-defined CRS. It also allows the user to define custom coordinate reference systems and supports on-the-fly (OTF) projection of vector and raster layers. All of these features allow the user to display layers with different CRSs and have them overlay properly. 10.1 Overview of Projection Support QGIS has support for approximately 2,700 known CRSs. Definitions for each CRS are stored in a SQLite database that is installed with QGIS. Normally, you do not need to manipulate the database directly. In fact, doing so may cause projection support to fail. Custom CRSs are stored in a user database. See section Custom Coordinate Reference System for information on managing your custom coordinate reference systems. The CRSs available in QGIS are based on those defined by the European Petroleum Search Group (EPSG) and the Institut Geographique National de France (IGNF) and are largely abstracted from the spatial reference tables used in GDAL. EPSG identifiers are present in the database and can be used to specify a CRS in QGIS. In order to use OTF projection, either your data must contain information about its coordinate reference system or you will need to define a global, layer or project-wide CRS. For PostGIS layers, QGIS uses the spatial reference identifier that was specified when the layer was created. For data supported by OGR, QGIS relies on the presence of a recognized means of specifying the CRS. In the case of shapefiles, this means a file containing the well-known text (WKT) specification of the CRS. This projection file has the same base name as the shapefile and a .prj extension. For example, a shapefile named alaska.shp would have a corresponding projection file named alaska.prj. Whenever you select a new CRS, the layer units will automatically be changed in the General tab of the Project Properties dialog under the Project (Gnome, OS X) or Settings (KDE, Windows) menu. 10.2 Global Projection Specification QGIS starts each new project using the global default projection. The global default CRS is EPSG:4326 - WGS 84 (proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs), and it comes predefined in QGIS. This default can be changed via the [Select...] button in the first section, which is used to define the default coordinate reference system for new projects, as shown in figure_projection_1. This choice will be saved for use in subsequent QGIS sessions. When you use layers that do not have a CRS, you need to define how QGIS responds to these layers. This can be done globally or project-wide in the CRS tab under Settings → Options. The options shown in figure_projection_1 are: • Prompt for CRS • Use project CRS 55 QGIS User Guide, Release 2.6 Figure 10.1: CRS tab in the QGIS Options Dialog 56 Chapter 10. Working with Projections QGIS User Guide, Release 2.6 • Use default CRS displayed below If you want to define the coordinate reference system for a certain layer without CRS information, you can also do that in the General tab of the raster and vector properties dialog (see General Menu for rasters and General Menu for vectors). If your layer already has a CRS defined, it will be displayed as shown in Vector Layer Properties Dialog . Tip: CRS in the Map Legend Right-clicking on a layer in the Map Legend (section Map Legend) provides two CRS shortcuts. Set layer CRS takes you directly to the Coordinate Reference System Selector dialog (see figure_projection_2). Set project CRS from Layer redefines the project CRS using the layer’s CRS. 10.3 Define On The Fly (OTF) Reprojection QGIS supports OTF reprojection for both raster and vector data. However, OTF is not activated by default. To use OTF projection, you must activate the Enable on the fly CRS transformation checkbox in the CRS tab of the Project Properties dialog. There are three ways to do this: 1. Select Project Properties from the Project (Gnome, OSX) or Settings (KDE, Windows) menu. 2. Click on the CRS status icon in the lower right-hand corner of the status bar. 3. Turn OTF on by default in the CRS tab of the Options dialog by selecting Enable ‘on the fly’ reprojection by default or Automatically enable ‘on the fly’ reprojection if layers have different CRS. If you have already loaded a layer and you want to enable OTF projection, the best practice is to open the CRS tab of the Project Properties dialog, select a CRS, and activate the Enable ‘on the fly’ CRS transformation checkbox. The CRS status icon will no longer be greyed out, and all layers will be OTF projected to the CRS shown next to the icon. The CRS tab of the Project Properties dialog contains five important components, as shown in Figure_projection_2 and described below: 1. Enable ‘on the fly’ CRS transformation — This checkbox is used to enable or disable OTF projection. When off, each layer is drawn using the coordinates as read from the data source, and the components de- scribed below are inactive. When on, the coordinates in each layer are projected to the coordinate reference system defined for the map canvas. 2. Filter — If you know the EPSG code, the identifier, or the name for a coordinate reference system, you can use the search feature to find it. Enter the EPSG code, the identifier or the name. 3. Recently used coordinate reference systems — If you have certain CRSs that you frequently use in your everyday GIS work, these will be displayed in this list. Click on one of these items to select the associated CRS. 4. Coordinate reference systems of the world — This is a list of all CRSs supported by QGIS, including Geographic, Projected and Custom coordinate reference systems. To define a CRS, select it from the list by expanding the appropriate node and selecting the CRS. The active CRS is preselected. 5. PROJ.4 text — This is the CRS string used by the PROJ.4 projection engine. This text is read-only and provided for informational purposes. Tip: Project Properties Dialog If you open the Project Properties dialog from the Project menu, you must click on the CRS tab to view the CRS settings. 10.3. Define On The Fly (OTF) Reprojection 57 QGIS User Guide, Release 2.6 Figure 10.2: Project Properties Dialog Opening the dialog from the CRS status icon will automatically bring the CRS tab to the front. 10.4 Custom Coordinate Reference System If QGIS does not provide the coordinate reference system you need, you can define a custom CRS. To define a CRS, select Custom CRS... from the Settings menu. Custom CRSs are stored in your QGIS user database. In addition to your custom CRSs, this database also contains your spatial bookmarks and other custom data. Defining a custom CRS in QGIS requires a good understanding of the PROJ.4 projection library. To begin, refer to “Cartographic Projection Procedures for the UNIX Environment - A User’s Manual” by Gerald I. Evenden, U.S. Geological Survey Open-File Report 90-284, 1990 (available at ftp://ftp.remotesensing.org/proj/OF90-284.pdf). This manual describes the use of the proj.4 and related command line utilities. The cartographic parameters used with proj.4 are described in the user manual and are the same as those used by QGIS. The Custom Coordinate Reference System Definition dialog requires only two parameters to define a user CRS: 1. A descriptive name 2. The cartographic parameters in PROJ.4 format To create a new CRS, click the Add new CRS button and enter a descriptive name and the CRS parameters. Note that the Parameters must begin with a +proj= block, to represent the new coordinate reference system. You can test your CRS parameters to see if they give sane results. To do this, enter known WGS 84 latitude and longitude values in North and East fields, respectively. Click on [Calculate], and compare the results with the known values in your coordinate reference system. 58 Chapter 10. Working with Projections QGIS User Guide, Release 2.6 Figure 10.3: Custom CRS Dialog 10.5 Default datum transformations OTF depends on being able to transform data into a ‘default CRS’, and QGIS uses WGS84. For some CRS there are a number of transforms available. QGIS allows you to define the transformation used otherwise QGIS uses a default transformation. In the CRS tab under Settings → Options you can: • set QGIS to ask you when it needs define a transformation using Ask for datum transformation when no default is defined • edit a list of user defaults for transformations. QGIS asks which transformation to use by opening a dialogue box displaying PROJ.4 text describing the source and destination transforms. Further information may be found by hovering over a transform. User defaults can be saved by selecting Remember selection. . 10.5. Default datum transformations 59 QGIS User Guide, Release 2.6 60 Chapter 10. Working with Projections CHAPTER 11 QGIS Browser The QGIS Browser is a panel in QGIS that lets you easily navigate in your filesystem and manage geodata. You can have access to common vector files (e.g., ESRI shapefiles or MapInfo files), databases (e.g., PostGIS, Oracle, SpatiaLite or MS SQL Spatial) and WMS/WFS connections. You can also view your GRASS data (to get the data into QGIS, see GRASS GIS Integration). Figure 11.1: QGIS browser as a stand alone application Use the QGIS Browser to preview your data. The drag-and-drop function makes it easy to get your data into the map view and the map legend. 1. Activate the QGIS Browser: Right-click on the toolbar and check Browser or select it from Settings → Panels. 2. Drag the panel into the legend window and release it. 3. Click on the Browser tab. 4. Browse in your filesystem and choose the shapefile folder from qgis_sample_data directory. 5. Press the Shift key and select the airports.shp and alaska.shp files. 6. Press the left mouse button, then drag and drop the files into the map canvas. 61 QGIS User Guide, Release 2.6 7. Right-click on a layer and choose Set project CRS from layer. For more information see Working with Projections. 8. Click on Zoom Full to make the layers visible. There is a second browser available under Settings → Panels. This is handy when you need to move files or layers between locations. 1. Activate a second QGIS Browser: Right-click on the toolbar and check Browser (2), or select it from Settings → Panels. 2. Drag the panel into the legend window. 3. Navigate to the Browser (2) tab and browse for a shapefile in your file system. 4. Select a file with the left mouse button. Now you can use the Add Selected Layers icon to add it into the current project. QGIS automatically looks for the coordinate reference system (CRS) and zooms to the layer extent if you work in a blank QGIS project. If there are already files in your project, the file will just be added, and in the case that it has the same extent and CRS, it will be visualized. If the file has another CRS and layer extent, you must first right-click on the layer and choose Set Project CRS from Layer. Then choose Zoom to Layer Extent. The Filter files function works on a directory level. Browse to the folder where you want to filter files and enter a search word or wildcard. The Browser will show only matching filenames – other data won’t be displayed. It’s also possible to run the QGIS Browser as a stand-alone application. Start the QGIS browser • Type in “qbrowser” at a command prompt. • Start the QGIS Browser using the Start menu or desktop shortcut. • The QGIS Browser is available from your Applications folder. In figure_browser_standalone_metadata, you can see the enhanced functionality of the stand-alone QGIS Browser. The Param tab provides the details of your connection-based datasets, like PostGIS or MSSQL Spatial. The Metadata tab contains general information about the file (see Metadata Menu). With the Preview tab, you can have a look at your files without importing them into your QGIS project. It’s also possible to preview the attributes of your files in the Attributes tab. . 62 Chapter 11. QGIS Browser CHAPTER 12 Working with Vector Data . 12.1 Supported Data Formats QGIS uses the OGR library to read and write vector data formats, including ESRI shapefiles, MapInfo and Micro- Station file formats, AutoCAD DXF, PostGIS, SpatiaLite, Oracle Spatial and MSSQL Spatial databases, and many more. GRASS vector and PostgreSQL support is supplied by native QGIS data provider plugins. Vector data can also be loaded in read mode from zip and gzip archives into QGIS. As of the date of this document, 69 vector formats are supported by the OGR library (see OGR-SOFTWARE-SUITE in Literature and Web References). The complete list is available at http://www.gdal.org/ogr/ogr_formats.html. Note: Not all of the listed formats may work in QGIS for various reasons. For example, some require external commercial libraries, or the GDAL/OGR installation of your OS may not have been built to support the format you want to use. Only those formats that have been well tested will appear in the list of file types when loading a vector into QGIS. Other untested formats can be loaded by selecting *.*. Working with GRASS vector data is described in Section GRASS GIS Integration. This section describes how to work with several common formats: ESRI shapefiles, PostGIS layers, SpatiaLite layers, OpenStreetMap vectors, and Comma Separated data (CSV). Many of the features available in QGIS work the same, regardless of the vector data source. This is by design, and it includes the identify, select, labeling and attributes functions. 12.1.1 ESRI Shapefiles The standard vector file format used in QGIS is the ESRI shapefile. Support is provided by the OGR Simple Feature Library (http://www.gdal.org/ogr/). A shapefile actually consists of several files. The following three are required: 1. .shp file containing the feature geometries 2. .dbf file containing the attributes in dBase format 3. .shx index file Shapefiles also can include a file with a .prj suffix, which contains the projection information. While it is very useful to have a projection file, it is not mandatory. A shapefile dataset can contain additional files. For further details, see the ESRI technical specification at http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf. 63 QGIS User Guide, Release 2.6 Loading a Shapefile To load a shapefile, start QGIS and click on the Add Vector Layer toolbar button, or simply press Ctrl+Shift+V. This will bring up a new window (see figure_vector_1). Figure 12.1: Add Vector Layer Dialog From the available options check File. Click on [Browse]. That will bring up a standard open file dialog (see figure_vector_2), which allows you to navigate the file system and load a shapefile or other supported data source. The selection box Filter allows you to preselect some OGR-supported file formats. You can also select the encoding for the shapefile if desired. Figure 12.2: Open an OGR Supported Vector Layer Dialog Selecting a shapefile from the list and clicking [Open] loads it into QGIS. Figure_vector_3 shows QGIS after loading the alaska.shp file. Tip: Layer Colors When you add a layer to the map, it is assigned a random color. When adding more than one layer at a time, different colors are assigned to each layer. Once a shapefile is loaded, you can zoom around it using the map navigation tools. To change the style of a layer, open the Layer Properties dialog by double clicking on the layer name or by right-clicking on the name in the 64 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.3: QGIS with Shapefile of Alaska loaded legend and choosing Properties from the context menu. See section Style Menu for more information on setting symbology of vector layers. Tip: Load layer and project from mounted external drives on OS X On OS X, portable drives that are mounted beside the primary hard drive do not show up as expected under File → Open Project. We are working on a more OSX-native open/save dialog to fix this. As a workaround, you can type /Volumes in the File name box and press Enter. Then you can navigate to external drives and network mounts. Improving Performance for Shapefiles To improve the performance of drawing a shapefile, you can create a spatial index. A spatial index will improve the speed of both zooming and panning. Spatial indexes used by QGIS have a .qix extension. Use these steps to create the index: • Load a shapefile by clicking on the Add Vector Layer toolbar button or pressing Ctrl+Shift+V. • Open the Layer Properties dialog by double-clicking on the shapefile name in the legend or by right-clicking and choosing Properties from the context menu. • In the General tab, click the [Create Spatial Index] button. Problem loading a shape .prj file If you load a shapefile with a .prj file and QGIS is not able to read the coordinate reference system from that file, you will need to define the proper projection manually within the General tab of the Layer Properties dialog 12.1. Supported Data Formats 65 QGIS User Guide, Release 2.6 of the layer by clicking the [Specify...] button. This is due to the fact that .prj files often do not provide the complete projection parameters as used in QGIS and listed in the CRS dialog. For the same reason, if you create a new shapefile with QGIS, two different projection files are created: a .prj file with limited projection parameters, compatible with ESRI software, and a .qpj file, providing the complete parameters of the used CRS. Whenever QGIS finds a .qpj file, it will be used instead of the .prj. 12.1.2 Loading a MapInfo Layer To load a MapInfo layer, click on the Add Vector Layer toolbar button; or type Ctrl+Shift+V, change the file type filter Files of type : to ‘Mapinfo File [OGR] (*.mif *.tab *.MIF *.TAB)’ and select the MapInfo layer you want to load. 12.1.3 Loading an ArcInfo Binary Coverage To load an ArcInfo Binary Coverage, click on the Add Vector Layer toolbar button or press Ctrl+Shift+V to open the Add Vector Layer dialog. Select Directory as Source type. Change the file type filter Files of type to ‘Arc/Info Binary Coverage’. Navigate to the directory that contains the coverage file, and select it. Similarly, you can load directory-based vector files in the UK National Transfer Format, as well as the raw TIGER Format of the US Census Bureau. 12.1.4 Delimited Text Files Tabular data is a very common and widely used format because of its simplicity and readability – data can be viewed and edited even in a plain text editor. A delimited text file is an attribute table with each column separated by a defined character and each row separated by a line break. The first row usually contains the column names. A common type of delimited text file is a CSV (Comma Separated Values), with each column separated by a comma. Such data files can also contain positional information in two main forms: • As point coordinates in separate columns • As well-known text (WKT) representation of geometry QGIS allows you to load a delimited text file as a layer or ordinal table. But first check that the file meets the following requirements: 1. The file must have a delimited header row of field names. This must be the first line in the text file. 2. The header row must contain field(s) with geometry definition. These field(s) can have any name. 3. The X and Y coordinates (if geometry is defined by coordinates) must be specified as numbers. The coor- dinate system is not important. As an example of a valid text file, we import the elevation point data file elevp.csv that comes with the QGIS sample dataset (see section Sample Data): X;Y;ELEV -300120;7689960;13 -654360;7562040;52 1640;7512840;3 [...] Some items to note about the text file: 1. The example text file uses ;(semicolon) as delimiter. Any character can be used to delimit the fields. 2. The first row is the header row. It contains the fields X,Y and ELEV. 3. No quotes (") are used to delimit text fields. 66 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 4. The X coordinates are contained in the X field. 5. The Y coordinates are contained in the Y field. Loading a delimited text file Click the toolbar icon Add Delimited Text Layer in the Manage layers toolbar to open the Create a Layer from a Delimited Text File dialog, as shown in figure_delimited_text_1. Figure 12.4: Delimited Text Dialog First, select the file to import (e.g., qgis_sample_data/csv/elevp.csv) by clicking on the [Browse] button. Once the file is selected, QGIS attempts to parse the file with the most recently used delimiter. To enable QGIS to properly parse the file, it is important to select the correct delimiter. You can specify a delimiter by activating Custom delimiters, or by activating Regular expression delimiter and entering text into the Expression field. For example, to change the delimiter to tab, use \t (this is a regular expression for the tab character). Once the file is parsed, set Geometry definition to Point coordinates and choose the X and Y fields from the dropdown lists. If the coordinates are defined as degrees/minutes/seconds, activate the DMS coordinates checkbox. Finally, enter a layer name (e.g., elevp), as shown in figure_delimited_text_1. To add the layer to the map, click [OK]. The delimited text file now behaves as any other map layer in QGIS. There is also a helper option that allows you to trim leading and trailing spaces from fields — Trim fields. Also, it is possible to Discard empty fields. If necessary, you can force a comma to be the decimal separator by activating Decimal separator is comma. If spatial information is represented by WKT, activate the Well Known Text option and select the field with the WKT definition for point, line or polygon objects. If the file contains non-spatial data, activate No geometry (attribute only table) and it will be loaded as an ordinal table. Additionaly, you can enable: • Use spatial index to improve the performance of displaying and spatially selecting features. 12.1. Supported Data Formats 67 QGIS User Guide, Release 2.6 • Use subset index. • Watch file to watch for changes to the file by other applications while QGIS is running. 12.1.5 OpenStreetMap data In recent years, the OpenStreetMap project has gained popularity because in many countries no free geodata such as digital road maps are available. The objective of the OSM project is to create a free editable map of the world from GPS data, aerial photography or local knowledge. To support this objective, QGIS provides suppport for OSM data. Loading OpenStreetMap Vectors QGIS integrates OpenStreetMap import as a core functionality. • To connect to the OSM server and download data, open the menu Vector → Openstreetmap → Load data. You can skip this step if you already obtained an .osm XML file using JOSM, Overpass API or any other source. • The menu Vector → Openstreetmap → Import topology from an XML file will convert your .osm file into a SpatiaLite database and create a corresponding database connection. • The menu Vector → Openstreetmap → Export topology to SpatiaLite then allows you to open the database connection, select the type of data you want (points, lines, or polygons) and choose tags to import. This creates a SpatiaLite geometry layer that you can add to your project by clicking on the Add SpatiaLite Layer toolbar button or by selecting the Add SpatiaLite Layer... option from the Layer menu (see section SpatiaLite Layers). 12.1.6 PostGIS Layers PostGIS layers are stored in a PostgreSQL database. The advantages of PostGIS are the spatial indexing, filter- ing and query capabilities it provides. Using PostGIS, vector functions such as select and identify work more accurately than they do with OGR layers in QGIS. Creating a stored Connection The first time you use a PostGIS data source, you must create a connection to the PostgreSQL database that contains the data. Begin by clicking on the Add PostGIS Layer toolbar button, selecting the Add PostGIS Layer... option from the Layer menu, or typing Ctrl+Shift+D. You can also open the Add Vector Layer dialog and select Database. The Add PostGIS Table(s) dialog will be displayed. To access the connection manager, click on the [New] button to display the Create a New PostGIS Connection dialog. The parameters required for a connection are: • Name: A name for this connection. It can be the same as Database. • Service: Service parameter to be used alternatively to hostname/port (and potentially database). This can be defined in pg_service.conf. • Host: Name of the database host. This must be a resolvable host name such as would be used to open a telnet connection or ping the host. If the database is on the same computer as QGIS, simply enter ‘localhost’ here. • Port: Port number the PostgreSQL database server listens on. The default port is 5432. • Database: Name of the database. 68 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 • SSL mode: How the SSL connection will be negotiated with the server. Note that massive speedups in PostGIS layer rendering can be achieved by disabling SSL in the connection editor. The following options are available: – Disable: Only try an unencrypted SSL connection. – Allow: Try a non-SSL connection. If that fails, try an SSL connection. – Prefer (the default): Try an SSL connection. If that fails, try a non-SSL connection. – Require: Only try an SSL connection. • Username: User name used to log in to the database. • Password: Password used with Username to connect to the database. Optionally, you can activate the following checkboxes: • Save Username • Save Password • Only look in the geometry_columns table • Don’t resolve type of unrestricted columns (GEOMETRY) • Only look in the ‘public’ schema • Also list tables with no geometry • Use estimated table metadata Once all parameters and options are set, you can test the connection by clicking on the [Test Connect] button. Loading a PostGIS Layer Once you have one or more connections defined, you can load layers from the PostgreSQL database. Of course, this requires having data in PostgreSQL. See section Importing Data into PostgreSQL for a discussion on importing data into the database. To load a layer from PostGIS, perform the following steps: • If the Add PostGIS layers dialog is not already open, selecting the Add PostGIS Layer... option from the Layer menu or typing Ctrl+Shift+D opens the dialog. • Choose the connection from the drop-down list and click [Connect]. • Select or unselect Also list tables with no geometry. • Optionally, use some Search Options to define which features to load from the layer, or use the [Build query] button to start the Query builder dialog. • Find the layer(s) you wish to add in the list of available layers. • Select it by clicking on it. You can select multiple layers by holding down the Shift key while clicking. See section Query Builder for information on using the PostgreSQL Query Builder to further define the layer. • Click on the [Add] button to add the layer to the map. Tip: PostGIS Layers Normally, a PostGIS layer is defined by an entry in the geometry_columns table. From version 0.9.0 on, QGIS can load layers that do not have an entry in the geometry_columns table. This includes both tables and views. Defining a spatial view provides a powerful means to visualize your data. Refer to your PostgreSQL manual for information on creating views. 12.1. Supported Data Formats 69 QGIS User Guide, Release 2.6 Some details about PostgreSQL layers This section contains some details on how QGIS accesses PostgreSQL layers. Most of the time, QGIS should simply provide you with a list of database tables that can be loaded, and it will load them on request. However, if you have trouble loading a PostgreSQL table into QGIS, the information below may help you understand any QGIS messages and give you direction on changing the PostgreSQL table or view definition to allow QGIS to load it. QGIS requires that PostgreSQL layers contain a column that can be used as a unique key for the layer. For tables, this usually means that the table needs a primary key, or a column with a unique constraint on it. In QGIS, this column needs to be of type int4 (an integer of size 4 bytes). Alternatively, the ctid column can be used as primary key. If a table lacks these items, the oid column will be used instead. Performance will be improved if the column is indexed (note that primary keys are automatically indexed in PostgreSQL). If the PostgreSQL layer is a view, the same requirement exists, but views do not have primary keys or columns with unique constraints on them. You have to define a primary key field (has to be integer) in the QGIS dialog before you can load the view. If a suitable column does not exist in the view, QGIS will not load the layer. If this occurs, the solution is to alter the view so that it does include a suitable column (a type of integer and either a primary key or with a unique constraint, preferably indexed). QGIS offers a checkbox Select at id that is activated by default. This option gets the ids without the attributes which is faster in most cases. It can make sense to disable this option when you use expensive views. 12.1.7 Importing Data into PostgreSQL Data can be imported into PostgreSQL/PostGIS using several tools, including the SPIT plugin and the command line tools shp2pgsql and ogr2ogr. DB Manager QGIS comes with a core plugin named DB Manager. It can be used to load shapefiles and other data formats, and it includes support for schemas. See section DB Manager Plugin for more information. shp2pgsql PostGIS includes an utility called shp2pgsql that can be used to import shapefiles into a PostGIS-enabled database. For example, to import a shapefile named lakes.shp into a PostgreSQL database named gis_data, use the following command: shp2pgsql -s 2964 lakes.shp lakes_new | psql gis_data This creates a new layer named lakes_new in the gis_data database. The new layer will have a spatial ref- erence identifier (SRID) of 2964. See section Working with Projections for more information on spatial reference systems and projections. Tip: Exporting datasets from PostGIS Like the import tool shp2pgsql, there is also a tool to export PostGIS datasets as shapefiles: pgsql2shp. This is shipped within your PostGIS distribution. ogr2ogr Besides shp2pgsql and DB Manager, there is another tool for feeding geodata in PostGIS: ogr2ogr. This is part of your GDAL installation. 70 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 To import a shapefile into PostGIS, do the following: ogr2ogr -f "PostgreSQL" PG:"dbname=postgis host=myhost.de user=postgres password=topsecret" alaska.shp This will import the shapefile alaska.shp into the PostGIS database postgis using the user postgres with the password topsecret on host server myhost.de. Note that OGR must be built with PostgreSQL to support PostGIS. You can verify this by typing (in ) ogrinfo --formats | grep -i post If you prefer to use PostgreSQL’s COPY command instead of the default INSERT INTO method, you can export the following environment variable (at least available on and ): export PG_USE_COPY=YES ogr2ogr does not create spatial indexes like shp2pgsl does. You need to create them manually, using the nor- mal SQL command CREATE INDEX afterwards as an extra step (as described in the next section Improving Performance). Improving Performance Retrieving features from a PostgreSQL database can be time-consuming, especially over a network. You can improve the drawing performance of PostgreSQL layers by ensuring that a PostGIS spatial index exists on each layer in the database. PostGIS supports creation of a GiST (Generalized Search Tree) index to speed up spatial searches of the data (GiST index information is taken from the PostGIS documentation available at http://postgis.refractions.net). The syntax for creating a GiST index is: CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometryfield] GIST_GEOMETRY_OPS ); Note that for large tables, creating the index can take a long time. Once the index is created, you should perform a VACUUM ANALYZE. See the PostGIS documentation (POSTGIS-PROJECT Literature and Web References) for more information. The following is an example of creating a GiST index: gsherman@madison:~/current$ psql gis_data Welcome to psql 8.3.0, the PostgreSQL interactive terminal. Type: \copyright for distribution terms \h for help with SQL commands \? for help with psql commands \g or terminate with semicolon to execute query \q to quit gis_data=# CREATE INDEX sidx_alaska_lakes ON alaska_lakes gis_data-# USING GIST (the_geom GIST_GEOMETRY_OPS); CREATE INDEX gis_data=# VACUUM ANALYZE alaska_lakes; VACUUM gis_data=# \q gsherman@madison:~/current$ 12.1.8 Vector layers crossing 180° longitude Many GIS packages don’t wrap vector maps with a geographic reference system (lat/lon) crossing the 180 degrees longitude line (http://postgis.refractions.net/documentation/manual-2.0/ST_Shift_Longitude.html). As result, if 12.1. Supported Data Formats 71 QGIS User Guide, Release 2.6 we open such a map in QGIS, we will see two far, distinct locations, that should appear near each other. In Figure_vector_4, the tiny point on the far left of the map canvas (Chatham Islands) should be within the grid, to the right of the New Zealand main islands. Figure 12.5: Map in lat/lon crossing the 180° longitude line A work-around is to transform the longitude values using PostGIS and the ST_Shift_Longitude function. This function reads every point/vertex in every component of every feature in a geometry, and if the longitude coordi- nate is < 0°, it adds 360° to it. The result is a 0° - 360° version of the data to be plotted in a 180°-centric map. Figure 12.6: Crossing 180° longitude applying the ST_Shift_Longitude function Usage • Import data into PostGIS (Importing Data into PostgreSQL) using, for example, the DB Manager plugin. • Use the PostGIS command line interface to issue the following command (in this example, “TABLE” is the actual name of your PostGIS table): gis_data=# update TABLE set the_geom=ST_Shift_Longitude(the_geom); • If everything went well, you should receive a confirmation about the number of features that were updated. Then you’ll be able to load the map and see the difference (Figure_vector_5). 12.1.9 SpatiaLite Layers The first time you load data from a SpatiaLite database, begin by clicking on the Add SpatiaLite Layer toolbar button, or by selecting the Add SpatiaLite Layer... option from the Layer menu, or by typing Ctrl+Shift+L. This will bring up a window that will allow you either to connect to a SpatiaLite database already known to QGIS, which you can choose from the drop-down menu, or to define a new connection to a new database. To define a new connection, click on [New] and use the file browser to point to your SpatiaLite database, which is a file with a .sqlite extension. 72 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 If you want to save a vector layer to SpatiaLite format, you can do this by right clicking the layer in the legend. Then, click on Save as.., define the name of the output file, and select ‘SpatiaLite’ as format and the CRS. Also, you can select ‘SQLite’ as format and then add SPATIALITE=YES in the OGR data source creation option field. This tells OGR to create a SpatiaLite database. See also http://www.gdal.org/ogr/drv_sqlite.html. QGIS also supports editable views in SpatiaLite. Creating a new SpatiaLite layer If you want to create a new SpatiaLite layer, please refer to section Creating a new SpatiaLite layer. Tip: SpatiaLite data management Plugins For SpatiaLite data management, you can also use several Python plugins: QSpatiaLite, SpatiaLite Manager or DB Manager (core plugin, recommended). If necessary, they can be downloaded and installed with the Plugin Installer. 12.1.10 MSSQL Spatial Layers QGIS also provides native MS SQL 2008 support. The first time you load MSSQL Spatial data, begin by clicking on the Add MSSQL Spatial Layer toolbar button or by selecting the Add MSSQL Spatial Layer... option from the Layer menu, or by typing Ctrl+Shift+M. 12.1.11 Oracle Spatial Layers The spatial features in Oracle Spatial aid users in managing geographic and location data in a native type within an Oracle database. QGIS now has support for such layers. Creating a stored Connection The first time you use an Oracle Spatial data source, you must create a connection to the database that contains the data. Begin by clicking on the Add Orcale Spatial Layer toolbar button, selecting the Add Orcale Spatial Layer... option from the Layer menu, or typing Ctrl+Shift+O. To access the connection manager, click on the [New] button to display the Create a New Oracle Spatial Connection dialog. The parameters required for a connection are: • Name: A name for this connection. It can be the same as Database • Database: SID or SERVICE_NAME of the Oracle instance. • Host: Name of the database host. This must be a resolvable host name such as would be used to open a telnet connection or ping the host. If the database is on the same computer as QGIS, simply enter ‘localhost’ here. • Port: Port number the PostgreSQL database server listens on. The default port is 1521. • Username: Username used to login to the database. • Password: Password used with Username to connect to the database. Optionally, you can activate following checkboxes: • Save Username Indicates whether to save the database username in the connection configuration. • Save Password Indicates whether to save the database password in the connection settings. 12.1. Supported Data Formats 73 QGIS User Guide, Release 2.6 • Only look in meta data table Restricts the displayed tables to those that are in the all_sdo_geom_metadata view. This can speed up the initial display of spatial tables. • Only look for user’s tables When searching for spatial tables, restrict the search to tables that are owned by the user. • Also list tables with no geometry Indicates that tables without geometry should also be listed by default. • Use estimated table statistics for the layer metadata When the layer is set up, various metadata are required for the Oracle table. This includes information such as the table row count, geometry type and spatial extents of the data in the geometry column. If the table contains a large number of rows, determining this metadata can be time-consuming. By activating this option, the following fast table metadata operations are done: Row count is determined from all_tables.num_rows. Table extents are always determined with the SDO_TUNE.EXTENTS_OF function, even if a layer filter is applied. Table geometry is determined from the first 100 non-null geometry rows in the table. • Only existing geometry types Only list the existing geometry types and don’t offer to add others. Once all parameters and options are set, you can test the connection by clicking on the [Test Connect] button. Tip: QGIS User Settings and Security Depending on your computing environment, storing passwords in your QGIS settings may be a security risk. Passwords are saved in clear text in the system configuration and in the project files! Your customized settings for QGIS are stored based on the operating system: • The settings are stored in your home directory in ~/.qgis2. • The settings are stored in the registry. Loading an Oracle Spatial Layer Once you have one or more connections defined, you can load layers from the Oracle database. Of course, this requires having data in Oracle. To load a layer from Oracle Spatial, perform the following steps: • If the Add Oracle Spatial layers dialog is not already open, click on the Add Oracle Spatial Layer toolbar button. • Choose the connection from the drop-down list and click [Connect]. • Select or unselect Also list tables with no geometry. • Optionally, use some Search Options to define which features to load from the layer or use the [Build query] button to start the Query builder dialog. • Find the layer(s) you wish to add in the list of available layers. • Select it by clicking on it. You can select multiple layers by holding down the Shift key while clicking. See section Query Builder for information on using the Oracle Query Builder to further define the layer. • Click on the [Add] button to add the layer to the map. Tip: Oracle Spatial Layers Normally, an Oracle Spatial layer is defined by an entry in the USER_SDO_METADATA table. . 74 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 12.2 The Symbol Library 12.2.1 Presentation The Symbol Library is the place where users can create generic symbols to be used in several QGIS projects. It allows users to export and import symbols, groups symbols and add, edit and remove symbols. You can open it with the Settings → Style Library or from the Style tab in the vector layer’s Properties. Share and import symbols Users can export and import symbols in two main formats: qml (QGIS format) and SLD (OGC standard). Note that SLD format is not fully supported by QGIS. share item displays a drop down list to let the user import or export symbols. Groups and smart groups Groups are categories of Symbols and smart groups are dynamic groups. To create a group, right-click on an existing group or on the main Groups directory in the left of the library. You can also select a group and click on the add item button. To add a symbol into a group, you can either right click on a symbol then choose Apply group and then the group name added before. There is a second way to add several symbols into group: just select a group and click and choose Group Symbols. All symbols display a checkbox that allow you to add the symbol into the selected groups. When finished, you can click on the same button, and choose Finish Grouping. Create Smart Symbols is similar to creating group, but instead select Smart Groups. The dialog box allow user to choose the expression to select symbols in order to appear in the smart group (contains some tags, member of a group, have a string in its name, etc.) Add, edit, remove symbol With the Style manager from the [Symbol] menu you can manage your symbols. You can add item, edit item, remove item and share item. ‘Marker’ symbols, ‘Line’ symbols, ‘Fill’ patterns and ‘colour ramps’ can be used to create the symbols. The symbols are then assigned to ‘All Symbols’, ‘Groups’ or ‘Smart groups’. For each kind of symbols, you will find always the same dialog structure: • at the top left side a symbol representation • under the symbol representation the symbol tree show the symbol layers • at the right you can setup some parameter (unit,transparency, color, size and rotation) • under these parameteres you find some symbol from the symbol library The symbol tree allow adding, removing or protect new simple symbol. You can move up or down the symbol layer. More detailed settings can be made when clicking on the second level in the Symbol layers dialog. You can define Symbol layers that are combined afterwards. A symbol can consist of several Symbol layers. Settings will be shown later in this chapter. Tip: Note that once you have set the size in the lower levels of the Symbol layers dialog, the size of the whole symbol can be changed with the Size menu in the first level again. The size of the lower levels changes accordingly, while the size ratio is maintained. 12.2. The Symbol Library 75 QGIS User Guide, Release 2.6 12.2.2 Marker Symbols Marker symbols have several symbol layer types: • Ellipse marker • Font marker • Simple marker (default) • SVG marker • Vector Field marker The following settings are possible: • Symbol layer type: You have the option to use Ellipse markers, Font markers, Simple markers, SVG markers and Vector Field markers. • colors • Size • Outline style • Outline width • Angle • Offset X,Y: You can shift the symbol in the x- or y-direction. • Anchor point • Data defined properties ... 12.2.3 Line Symbols Line marker symbols have only two symbol layer types: • Marker line • Simple line (default) The default symbol layer type draws a simple line whereas the other display a marker point regularly on the line. You can choose different location vertex, interval or central point. Marker line can have offset along the line or offset line. Finally, rotation allows you to change the orientation of the symbol. The following settings are possible: • colour • Pen width • Offset • Pen style • Join style • Cap style • Use custom dash pattern • Dash pattern unit • Data defined properties ... 76 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 12.2.4 Polygon Symbols Polygon marker symbols have also several symbol layer types: • Centroid fill • Gradient fill • Line pattern fill • Point pattern fill • SVG fill • Shapeburst fille • Simple fill (default) • Outline: Marker line (same as line marker) • Outline: simple line (same as line marker) The following settings are possible: • Colors for the border and the fill. • Fill style • Border style • Border width • Offset X,Y • Data defined properties ... Using the color combo box, you can drag and drop color for one color button to another button, copy-paste color, pick color from somewhere, choose a color from the palette or from recent or standard color. The combo box allow you to fill in the feature with transparency. You can also just clic on the button to open the palettte dialog. Note that you can import color from some external software like GIMP. ‘Gradient Fill’ Symbol layer type allows you to select between a Two color and Color ramp setting. You can use the Feature centroid as Referencepoint. All fills ‘Gradient Fill‘ Symbol layer type is also available through the Symbol menu of the Categorized and Graduated Renderer and through the Rule properties menu of the Rule-based renderer. Other possibility is to choose a ‘shapeburst fill’ which is a buffered gradient fill, where a gradient is drawn from the boundary of a polygon towards the polygon’s centre. Configurable parameters include distance from the boundary to shade, use of color ramps or simple two color gradients, optional blurring of the fill and offsets. It is possible to only draw polygon borders inside the polygon. Using ‘Outline: Simple line’ select Draw line only inside polygon. 12.2.5 Color ramp You can create a custom color ramp choosing New color ramp... from the color ramp drop-down menu. A dialog will prompt for the ramp type: Gradient, Random, colorBrewer, or cpt-city. The first three have options for number of steps and/or multiple stops in the color ramp. You can use the Invert option while classifying the data with a color ramp. See figure_symbology_3 for an example of custom color ramp and figure_symbology_3a for the cpt-city dialog. The cpt-city option opens a new dialog with hundreds of themes included ‘out of the box’. . 12.2. The Symbol Library 77 QGIS User Guide, Release 2.6 Figure 12.7: Example of custom gradient color ramp with multiple stops Figure 12.8: cpt-city dialog with hundreds of color ramps 78 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 12.3 The Vector Properties Dialog The Layer Properties dialog for a vector layer provides information about the layer, symbology settings and labeling options. If your vector layer has been loaded from a PostgreSQL/PostGIS datastore, you can also alter the underlying SQL for the layer by invoking the Query Builder dialog on the General tab. To access the Layer Properties dialog, double-click on a layer in the legend or right-click on the layer and select Properties from the pop-up menu. Figure 12.9: Vector Layer Properties Dialog 12.3.1 Style Menu The Style menu provides you with a comprehensive tool for rendering and symbolizing your vector data. You can use Layer rendering → tools that are common to all vector data, as well as special symbolizing tools that were designed for the different kinds of vector data. Renderers The renderer is responsible for drawing a feature together with the correct symbol. There are four types of renderers: single symbol, categorized, graduated and rule-based. There is no continuous color renderer, because it is in fact only a special case of the graduated renderer. The categorized and graduated renderers can be created by specifying a symbol and a color ramp - they will set the colors for symbols appropriately. For point layers, there is a point displacement renderer available. For each data type (points, lines and polygons), vector symbol layer types are available. Depending on the chosen renderer, the Style menu provides different additional sections. On the bottom right of the symbology dialog, there is a [Symbol] button, which gives access to the Style Manager (see Presentation). The Style Manager allows you to edit and remove existing symbols and add new ones. 12.3. The Vector Properties Dialog 79 QGIS User Guide, Release 2.6 After having made any needed changes, the symbol can be added to the list of current style symbols (using [Symbol] Save in symbol library), and then it can easily be used in the future. Furthermore, you can use the [Save Style] button to save the symbol as a QGIS layer style file (.qml) or SLD file (.sld). SLDs can be exported from any type of renderer – single symbol, categorized, graduated or rule-based – but when importing an SLD, either a single symbol or rule-based renderer is created. That means that categorized or graduated styles are converted to rule-based. If you want to preserve those renderers, you have to stick to the QML format. On the other hand, it can be very handy sometimes to have this easy way of converting styles to rule-based. If you change the renderer type when setting the style of a vector layer the settings you made for the symbol will be maintained. Be aware that this procedure only works for one change. If you repeat changing the renderer type the settings for the symbol will get lost. If the datasource of the layer is a database (PostGIS or Spatialite for example), you can save your layer style inside a table of the database. Just clic on :guilabel:‘ Save Style‘ comboxbox and choose Save in database item then fill in the dialog to define a style name, add a description, an ui file and if the style is a default style. When loading a layer from the database, if a style already exists for this layer, QGIS will load the layer and its style. You can add several style in the database. Only one will be the default style anyway. Figure 12.10: Save Style in database Dialog Tip: Select and change multiple symbols The Symbology allows you to select multiple symbols and right click to change color, transparency, size, or width of selected entries. Single Symbol Renderer The Single Symbol Renderer is used to render all features of the layer using a single user-defined symbol. The properties, which can be adjusted in the Style menu, depend partially on the type of layer, but all types share the following dialog structure. In the top-left part of the menu, there is a preview of the current symbol to be rendered. On the right part of the menu, there is a list of symbols already defined for the current style, prepared to be used by selecting them from the list. The current symbol can be modified using the menu on the right side. If you click on the first level in the Symbol layers dialog on the left side, it’s possible to define basic parameters like Size, Transparency, color and Rotation. Here, the layers are joined together. Categorized Renderer The Categorized Renderer is used to render all features from a layer, using a single user-defined symbol whose color reflects the value of a selected feature’s attribute. The Style menu allows you to select: • The attribute (using the Column listbox or the Set column expression function, see Expressions) • The symbol (using the Symbol dialog) • The colors (using the color Ramp listbox) Then click on Classify button to create classes from the distinct value of the attribute column. Each classes can be disabled unchecking the checkbox at the left of the class name. 80 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.11: Single symbol line properties You can change symbol, value and/or label of the clic, just double clicking on the item you want to change. Right-clic shows a contextual menu to Copy/Paste, Change color, Change transparency, Change output unit, Change symbol width. The [Advanced] button in the lower-right corner of the dialog allows you to set the fields containing rotation and size scale information. For convenience, the center of the menu lists the values of all currently selected attributes together, including the symbols that will be rendered. The example in figure_symbology_2 shows the category rendering dialog used for the rivers layer of the QGIS sample dataset. Graduated Renderer The Graduated Renderer is used to render all the features from a layer, using a single user-defined symbol whose color reflects the assignment of a selected feature’s attribute to a class. Like the Categorized Renderer, the Graduated Renderer allows you to define rotation and size scale from specified columns. Also, analogous to the Categorized Renderer, the Style tab allows you to select: • The attribute (using the Column listbox or the Set column expression function, see Expressions chapter) • The symbol (using the Symbol Properties button) • The colors (using the color Ramp list) Additionally, you can specify the number of classes and also the mode for classifying features within the classes (using the Mode list). The available modes are: • Equal Interval: each class has the same size (e.g. values from 0 to 16 and 4 classes, each class has a size of 4); • Quantile: each class will have the same number of element inside (the idea of a boxplot); • Natural Breaks (Jenks): the variance within each class is minimal while the variance between classes is maximal; • Standard Deviation: classes are built depending on the standard deviation of the values; 12.3. The Vector Properties Dialog 81 QGIS User Guide, Release 2.6 Figure 12.12: Categorized Symbolizing options Figure 12.13: Graduated Symbolizing options 82 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 • Pretty Breaks: the same of natural breaks but the extremes number of each class are integers. The listbox in the center part of the Style menu lists the classes together with their ranges, labels and symbols that will be rendered. Click on Classify button to create classes using the choosen mode. Each classes can be disabled unchecking the checkbox at the left of the class name. You can change symbol, value and/or label of the clic, just double clicking on the item you want to change. Right-clic shows a contextual menu to Copy/Paste, Change color, Change transparency, Change output unit, Change symbol width. The example in figure_symbology_4 shows the graduated rendering dialog for the rivers layer of the QGIS sample dataset. Tip: Thematic maps using an expression Categorized and graduated thematic maps can now be created using the result of an expression. In the properties dialog for vector layers, the attribute chooser has been augmented with a Set column expression function. So now you no longer need to write the classification attribute to a new column in your attribute table if you want the classification attribute to be a composite of multiple fields, or a formula of some sort. Rule-based rendering The Rule-based Renderer is used to render all the features from a layer, using rule based symbols whose color reflects the assignment of a selected feature’s attribute to a class. The rules are based on SQL statements. The dialog allows rule grouping by filter or scale, and you can decide if you want to enable symbol levels or use only the first-matched rule. The example in figure_symbology_5 shows the rule-based rendering dialog for the rivers layer of the QGIS sample dataset. To create a rule, activate an existing row by double-clicking on it, or click on ‘+’ and click on the new rule. In the Rule properties dialog, you can define a label for the rule. Press the button to open the expression string builder. In the Function List, click on Fields and Values to view all attributes of the attribute table to be searched. To add an attribute to the field calculator Expression field, double click its name in the Fields and Values list. Generally, you can use the various fields, values and functions to construct the calculation expression, or you can just type it into the box (see Expressions). You can create a new rule by copying and pasting an existing rule with the right mouse button. You can also use the ‘ELSE’ rule that will be run if none of the other rules on that level match. Since QGIS 2.6 the label for the rules appears in a pseudotree in the map legend. Just double-klick the rules in the map legend and the Style menu of the layer properties appears showing the rule that is the background for the symbol in the pseudotree. Point displacement The Point Displacement Renderer works to visualize all features of a point layer, even if they have the same location. To do this, the symbols of the points are placed on a displacement circle around a center symbol. Tip: Export vector symbology You have the option to export vector symbology from QGIS into Google *.kml, *.dxf and MapInfo *.tab files. Just open the right mouse menu of the layer and click on Save selection as → to specify the name of the output file and its format. In the dialog, use the Symbology export menu to save the symbology either as Feature symbology → or as Symbol layer symbology →. If you have used symbol layers, it is recommended to use the second setting. Inverted Polygon Inverted polygon renderer allows user to define a symbol to fill in outside of the layer’s polygons. As before you can select a subrenderers. These subrenderers are the same as for the main renderers. 12.3. The Vector Properties Dialog 83 QGIS User Guide, Release 2.6 Figure 12.14: Rule-based Symbolizing options Figure 12.15: Point displacement dialog 84 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.16: Inverted Polygon dialog Color Picker Regardless the type of style to be used, the select color dialog will show when you click to choose a color - either border or fill color. This dialog has four different tabs which allow you to select colors by color ramp, color wheel, color swatches or color picker. Whatever method you use, the selected color is always described through color sliders for HSV (Hue, Saturation, Value) and RGB (Red, Green, Blue) values. There is also an opacity slider to set transparency level. On the lower left part of the dialog you can see a comparison between the current and the new color you are presently selecting and on the lower right part you have the option to add the color you just tweaked into a color slot button. With color ramp or with color wheel, you can browse to all possible color combinations. There are other possibilities though. By using color swatches you can choose from a preselected list. This selected list is populated with one of three methods: Recent colors, Standard colors or Project colors Another option is to use the color picker which allows you to sample a color from under your mouse pointer at any part of QGIS or even from another application by pressing the space bar. Please note that the color picker is OS dependent and is currently not supported by OSX. Tip: quick color picker + copy/paste colors You can quickly choose from Recent colors, from Standard colors or simply copy or paste a color by clicking the drop-down arrow that follows a current color box. Layer rendering • Layer transparency : You can make the underlying layer in the map canvas visible with this tool. Use the slider to adapt the visibility of your vector layer to your needs. You can also make a 12.3. The Vector Properties Dialog 85 QGIS User Guide, Release 2.6 Figure 12.17: Color picker ramp tab Figure 12.18: Color picker swatcher tab Figure 12.19: Quick color picker menu 86 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 precise definition of the percentage of visibility in the the menu beside the slider. • Layer blending mode and Feature blending mode: You can achieve special rendering effects with these tools that you may previously only know from graphics programs. The pixels of your overlaying and underlaying layers are mixed through the settings described below. – Normal: This is the standard blend mode, which uses the alpha channel of the top pixel to blend with the pixel beneath it. The colors aren’t mixed. – Lighten: This selects the maximum of each component from the foreground and background pixels. Be aware that the results tend to be jagged and harsh. – Screen: Light pixels from the source are painted over the destination, while dark pixels are not. This mode is most useful for mixing the texture of one layer with another layer (e.g., you can use a hillshade to texture another layer). – Dodge: Dodge will brighten and saturate underlying pixels based on the lightness of the top pixel. So, brighter top pixels cause the saturation and brightness of the underlying pixels to increase. This works best if the top pixels aren’t too bright; otherwise the effect is too extreme. – Addition: This blend mode simply adds pixel values of one layer with the other. In case of values above one (in the case of RGB), white is displayed. This mode is suitable for highlighting features. – Darken: This creates a resultant pixel that retains the smallest components of the foreground and background pixels. Like lighten, the results tend to be jagged and harsh. – Multiply: Here, the numbers for each pixel of the top layer are multiplied with the corresponding pixels for the bottom layer. The results are darker pictures. – Burn: Darker colors in the top layer cause the underlying layers to darken. Burn can be used to tweak and colorise underlying layers. – Overlay: This mode combines the multiply and screen blending modes. In the resulting picture, light parts become lighter and dark parts become darker. – Soft light: This is very similar to overlay, but instead of using multiply/screen it uses color burn/dodge. This is supposed to emulate shining a soft light onto an image. – Hard light: Hard light is also very similar to the overlay mode. It’s supposed to emulate projecting a very intense light onto an image. – Difference: Difference subtracts the top pixel from the bottom pixel, or the other way around, to always get a positive value. Blending with black produces no change, as the difference with all colors is zero. – Subtract: This blend mode simply subtracts pixel values of one layer from the other. In case of negative values, black is displayed. 12.3.2 Labels Menu The Labels core application provides smart labeling for vector point, line and polygon layers, and it only requires a few parameters. This new application also supports on-the-fly transformed layers. The core functions of the application have been redesigned. In QGIS, there are a number of other features that improve the labeling. The following menus have been created for labeling the vector layers: • Text • Formatting • Buffer • Background • Shadow • Placement 12.3. The Vector Properties Dialog 87 QGIS User Guide, Release 2.6 • Rendering Let us see how the new menus can be used for various vector layers. Labeling point layers Start QGIS and load a vector point layer. Activate the layer in the legend and click on the Layer Labeling Options icon in the QGIS toolbar menu. The first step is to activate the Label this layer with checkbox and select an attribute column to use for labeling. Click if you want to define labels based on expressions - See labeling_with_expressions. The following steps describe a simple labeling without using the Data defined override functions, which are situated next to the drop-down menus. You can define the text style in the Text menu (see Figure_labels_1 ). Use the Type case option to influence the text rendering. You have the possibility to render the text ‘All uppercase’, ‘All lowercase’ or ‘Capitalize first letter’. Use the blend modes to create effects known from graphics programs (see blend_modes). In the Formatting menu, you can define a character for a line break in the labels with the ‘Wrap on character’ function. Use the Formatted numbers option to format the numbers in an attribute table. Here, decimal places may be inserted. If you enable this option, three decimal places are initially set by default. To create a buffer, just activate the Draw text buffer checkbox in the Buffer menu. The buffer color is variable. Here, you can also use blend modes (see blend_modes). If the color buffer’s fill checkbox is activated, it will interact with partially transparent text and give mixed color transparency results. Turning off the buffer fill fixes that issue (except where the interior aspect of the buffer’s stroke intersects with the text’s fill) and also allows you to make outlined text. In the Background menu, you can define with Size X and Size Y the shape of your background. Use Size type to insert an additional ‘Buffer’ into your background. The buffer size is set by default here. The background then consists of the buffer plus the background in Size X and Size Y. You can set a Rotation where you can choose between ‘Sync with label’, ‘Offset of label’ and ‘Fixed’. Using ‘Offset of label’ and ‘Fixed’, you can rotate the background. Define an Offset X,Y with X and Y values, and the background will be shifted. When applying Radius X,Y, the background gets rounded corners. Again, it is possible to mix the background with the underlying layers in the map canvas using the Blend mode (see blend_modes). Use the Shadow menu for a user-defined Drop shadow. The drawing of the background is very variable. Choose between ‘Lowest label component’, ‘Text’, ‘Buffer’ and ‘Background’. The Offset angle depends on the orienta- tion of the label. If you choose the Use global shadow checkbox, then the zero point of the angle is always oriented to the north and doesn’t depend on the orientation of the label. You can influence the appearance of the shadow with the Blur radius. The higher the number, the softer the shadows. The appearance of the drop shadow can also be altered by choosing a blend mode (see blend_modes). Choose the Placement menu for the label placement and the labeling priority. Using the Offset from point setting, you now have the option to use Quadrants to place your label. Additionally, you can alter the angle of the label placement with the Rotation setting. Thus, a placement in a certain quadrant with a certain rotation is possible. In the Rendering menu, you can define label and feature options. Under Label options, you find the scale-based visibility setting now. You can prevent QGIS from rendering only selected labels with the Show all labels for this layer (including colliding labels) checkbox. Under Feature options, you can define whether every part of a multipart feature is to be labeled. It’s possible to define whether the number of features to be labeled is limited and to Discourage labels from covering features. Labeling line layers The first step is to activate the Label this layer checkbox in the Label settings tab and select an attribute column to use for labeling. Click if you want to define labels based on expressions - See labeling_with_expressions. After that, you can define the text style in the Text menu. Here, you can use the same settings as for point layers. Also, in the Formatting menu, the same settings as for point layers are possible. 88 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.20: Smart labeling of vector point layers The Buffer menu has the same functions as described in section labeling_point_layers. The Background menu has the same entries as described in section labeling_point_layers. Also, the Shadow menu has the same entries as described in section labeling_point_layers. In the Placement menu, you find special settings for line layers. The label can be placed Parallel, Curved or Horizontal. With the Parallel and Curved option, you can define the position Above line, On line and Below line. It’s possible to select several options at once. In that case, QGIS will look for the optimal position of the label. Remember that here you can also use the line orientation for the position of the label. Additionally, you can define a Maximum angle between curved characters when selecting the Curved option (see Figure_labels_2). You can set up a minimum distance for repeating labels. Distance can be in mm or in map units. Some Placement setup will display more options, for example, Curved and Parallel Placements will allow the user to set up the position of the label (above, belw or on the line), distance from the line and for Curved, the user can also setup inside/outside max angle between curved label. The Rendering menu has nearly the same entries as for point layers. In the Feature options, you can now Suppress labeling of features smaller than. Labeling polygon layers The first step is to activate the Label this layer checkbox and select an attribute column to use for labeling. Click if you want to define labels based on expressions - See labeling_with_expressions. In the Text menu, define the text style. The entries are the same as for point and line layers. The Formatting menu allows you to format multiple lines, also similar to the cases of point and line layers. As with point and line layers, you can create a text buffer in the Buffer menu. 12.3. The Vector Properties Dialog 89 QGIS User Guide, Release 2.6 Figure 12.21: Smart labeling of vector line layers Use the Background menu to create a complex user-defined background for the polygon layer. You can use the menu also as with the point and line layers. The entries in the Shadow menu are the same as for point and line layers. In the Placement menu, you find special settings for polygon layers (see Figure_labels_3). Offset from centroid, Horizontal (slow), Around centroid, Free and Using perimeter are possible. In the Offset from centroid settings, you can specify if the centroid is of the visible polygon or whole polygon. That means that either the centroid is used for the polygon you can see on the map or the centroid is determined for the whole polygon, no matter if you can see the whole feature on the map. You can place your label with the quadrants here, and define offset and rotation. The Around centroid setting makes it possible to place the label around the centroid with a certain distance. Again, you can define visible polygon or whole polygon for the centroid. With the Using perimeter settings, you can define a position and a distance for the label. For the position, Above line, On line, Below line and Line orientation dependent position are possible. Related to the choose of Label Placement, several options will appear. As for Point Placement you can choose the distance for the polygon outline, repeat the label around the polygon perimeter. The entries in the Rendering menu are the same as for line layers. You can also use Suppress labeling of features smaller than in the Feature options. Define labels based on expressions QGIS allows to use expressions to label features. Just click the icon in the Labels menu of the properties dialog. In figure_labels_4 you see a sample expression to label the alaska regions with name and area size, based on the field ‘NAME_2’, some descriptive text and the function ‘$area()’ in combination with ‘format_number()’ to make it look nicer. Expression based labeling is easy to work with. All you have to take care of is, that you need to combine all elements (strings, fields and functions) with a string concatenation sign ‘||’ and that fields a written in “double quotes” and strings in ‘single quotes’. Let’s have a look at some examples: # label based on two fields ’name’ and ’place’ with a comma as separater "name" || ’, ’ || "place" 90 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.22: Smart labeling of vector polygon layers Figure 12.23: Using expressions for labeling 12.3. The Vector Properties Dialog 91 QGIS User Guide, Release 2.6 -> John Smith, Paris # label based on two fields ’name’ and ’place’ separated by comma ’My name is ’ || "name" || ’and I live in ’ || "place" -> My name is John Smith and I live in Paris # label based on two fields ’name’ and ’place’ with a descriptive text # and a line break (\n) ’My name is ’ || "name" || ’\nI live in ’ || "place" -> My name is John Smith I live in Paris # create a multi-line label based on a field and the $area function # to show the place name and its area size based on unit meter. ’The area of ’ || "place" || ’has a size of ’ || $area || ’m²’ -> The area of Paris has a size of 105000000 m² # create a CASE ELSE condition. If the population value in field # population is <= 50000 it is a town, otherwise a city. ’This place is a ’ || CASE WHEN "population <= 50000" THEN ’town’ ELSE ’city’ END -> This place is a town As you can see in the expression builder, you have hundreds if functions available to create simple and very complex expressions to label your data in QGIS. See Expressions chapter for more information and example on expressions. Using data-defined override for labeling With the data-defined override functions, the settings for the labeling are overridden by entries in the attribute table. You can activate and deactivate the function with the right-mouse button. Hover over the symbol and you see the information about the data-defined override, including the current definition field. We now describe an example using the data-defined override function for the Move label function (see figure_labels_5). 1. Import lakes.shp from the QGIS sample dataset. 2. Double-click the layer to open the Layer Properties. Click on Labels and Placement. Select Offset from centroid. 3. Look for the Data defined entries. Click the icon to define the field type for the Coordinate. Choose ‘xlabel’ for X and ‘ylabel’ for Y. The icons are now highlighted in yellow. 4. Zoom into a lake. 5. Go to the Label toolbar and click the icon. Now you can shift the label manually to another position (see figure_labels_6 ). The new position of the label is saved in the ‘xlabel’ and ‘ylabel’ columns of the attribute table. 12.3.3 Fields Menu Within the Fields menu, the field attributes of the selected dataset can be manipulated. The buttons New Column and Delete Column can be used when the dataset is in Editing mode. Edit Widget Within the Fields menu, you also find an edit widget column. This column can be used to define values or a range of values that are allowed to be added to the specific attribute table column. If you click on the [edit widget] button, a dialog opens, where you can define different widgets. These widgets are: 92 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.24: Labeling of vector polygon layers with data-defined override Figure 12.25: Move labels 12.3. The Vector Properties Dialog 93 QGIS User Guide, Release 2.6 Figure 12.26: Dialog to select an edit widget for an attribute column 94 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 • Checkbox: Displays a checkbox, and you can define what attribute is added to the column when the check- box is activated or not. • Classification: Displays a combo box with the values used for classification, if you have chosen ‘unique value’ as legend type in the Style menu of the properties dialog. • Color: Displays a color button allowing user to choose a color from the color dialog window. • Date/Time: Displays a line fields which can opens a calendar widget to enter a date, a time or both. Column type must be text. You can select a custom format, pop-up a calendar, etc. • Enumeration: Opens a combo box with values that can be used within the columns type. This is currently only supported by the PostgreSQL provider. • File name: Simplifies the selection by adding a file chooser dialog. • Hidden: A hidden attribute column is invisible. The user is not able to see its contents. • Photo: Field contains a filename for a picture. The width and height of the field can be defined. • Range: Allows you to set numeric values from a specific range. The edit widget can be either a slider or a spin box. • Relation Reference: This widged lets you embed the feature form of the referenced layer on the feature form of the actual layer. See Creating one to many relations. • Text edit (default): This opens a text edit field that allows simple text or multiple lines to be used. If you choose multiple lines you can also choose html content. • Unique values: You can select one of the values already used in the attribute table. If ‘Editable’ is activated, a line edit is shown with autocompletion support, otherwise a combo box is used. • UUID Generator: Generates a read-only UUID (Universally Unique Identifiers) field, if empty. • Value map: A combo box with predefined items. The value is stored in the attribute, the description is shown in the combo box. You can define values manually or load them from a layer or a CSV file. • Value Relation: Offers values from a related table in a combobox. You can select layer, key column and value column. • Webview: Field contains a URL. The width and height of the field is variable. With the Attribute editor layout, you can now define built-in forms for data entry jobs (see figure_fields_2). Choose ‘Drag and drop designer’ and an attribute column. Use the icon to create a category that will then be shown during the digitizing session (see figure_fields_3). The next step will be to assign the relevant fields to the category with the icon. You can create more categories and use the same fields again. When creating a new category, QGIS will insert a new tab for the category in the built-in form. Other options in the dialog are ‘Autogenerate’ and ‘Provide ui-file’. ‘Autogenerate’ just creates editors for all fields and tabulates them. The ‘Provide ui-file’ option allows you to use complex dialogs made with the Qt- Designer. Using a UI-file allows a great deal of freedom in creating a dialog. For detailed information, see http://nathanw.net/2011/09/05/qgis-tips-custom-feature-forms-with-python-logic/. QGIS dialogs can have a Python function that is called when the dialog is opened. Use this function to add extra logic to your dialogs. An example is (in module MyForms.py): def open(dialog,layer,feature): geom = feature.geometry() control = dialog.findChild(QWidged,"My line edit") Reference in Python Init Function like so: MyForms.open MyForms.py must live on PYTHONPATH, in .qgis2/python, or inside the project folder. 12.3. The Vector Properties Dialog 95 QGIS User Guide, Release 2.6 Figure 12.27: Dialog to create categories with the Attribute editor layout Figure 12.28: Resulting built-in form in a data entry session 96 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 12.3.4 General Menu Use this menu to make general settings for the vector layer. There are several options available: Layer Info • Change the display name of the layer in displayed as • Define the Layer source of the vector layer • Define the Data source encoding to define provider-specific options and to be able to read the file Coordinate Reference System • Specify the coordinate reference system. Here, you can view or change the projection of the specific vector layer. • Create a Spatial Index (only for OGR-supported formats) • Update Extents information for a layer • View or change the projection of the specific vector layer, clicking on Specify ... Scale dependent visibility • You can set the Maximum (inclusive) and Minimum (exclusive) scale. The scale can also be set by the [Current] buttons. Feature subset • With the [Query Builder] button, you can create a subset of the features in the layer that will be visualized (also refer to section Query Builder). Figure 12.29: General menu in vector layers properties dialog 12.3. The Vector Properties Dialog 97 QGIS User Guide, Release 2.6 12.3.5 Rendering Menu QGIS 2.2 introduces support for on-the-fly feature generalisation. This can improve rendering times when drawing many complex features at small scales. This feature can be enabled or disabled in the layer settings using the Simplify geometry option. There is also a new global setting that enables generalisation by default for newly added layers (see section Options). Note: Feature generalisation may introduce artefacts into your rendered output in some cases. These may include slivers between polygons and inaccurate rendering when using offset-based symbol layers. 12.3.6 Display Menu This menu is specifically created for Map Tips. It includes a new feature: Map Tip display text in HTML. While you can still choose a Field to be displayed when hovering over a feature on the map, it is now possible to insert HTML code that creates a complex display when hovering over a feature. To activate Map Tips, select the menu option View → MapTips. Figure Display 1 shows an example of HTML code. Figure 12.30: HTML code for map tip 12.3.7 Actions Menu QGIS provides the ability to perform an action based on the attributes of a feature. This can be used to perform any number of actions, for example, running a program with arguments built from the attributes of a feature or passing parameters to a web reporting tool. Actions are useful when you frequently want to run an external application or view a web page based on one or more values in your vector layer. They are divided into six types and can be used like this: • Generic, Mac, Windows and Unix actions start an external process. • Python actions execute a Python expression. • Generic and Python actions are visible everywhere. • Mac, Windows and Unix actions are visible only on the respective platform (i.e., you can define three ‘Edit’ actions to open an editor and the users can only see and execute the one ‘Edit’ action for their platform to run the editor). 98 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.31: Map tip made with HTML code Figure 12.32: Overview action dialog with some sample actions 12.3. The Vector Properties Dialog 99 QGIS User Guide, Release 2.6 There are several examples included in the dialog. You can load them by clicking on [Add default actions]. One example is performing a search based on an attribute value. This concept is used in the following discussion. Defining Actions Attribute actions are defined from the vector Layer Properties dialog. To define an action, open the vector Layer Properties dialog and click on the Actions menu. Go to the Action properties. Select ‘Generic’ as type and provide a descriptive name for the action. The action itself must contain the name of the application that will be executed when the action is invoked. You can add one or more attribute field values as arguments to the application. When the action is invoked, any set of characters that start with a % followed by the name of a field will be replaced by the value of that field. The special characters %% will be replaced by the value of the field that was selected from the identify results or attribute table (see using_actions below). Double quote marks can be used to group text into a single argument to the program, script or command. Double quotes will be ignored if preceded by a backslash. If you have field names that are substrings of other field names (e.g., col1 and col10), you should indicate that by surrounding the field name (and the % character) with square brackets (e.g., [%col10]). This will prevent the %col10 field name from being mistaken for the %col1 field name with a 0 on the end. The brackets will be removed by QGIS when it substitutes in the value of the field. If you want the substituted field to be surrounded by square brackets, use a second set like this: [[%col10]]. Using the Identify Features tool, you can open the Identify Results dialog. It includes a (Derived) item that contains information relevant to the layer type. The values in this item can be accessed in a similar way to the other fields by preceeding the derived field name with (Derived).. For example, a point layer has an X and Y field, and the values of these fields can be used in the action with %(Derived).X and %(Derived).Y. The derived attributes are only available from the Identify Results dialog box, not the Attribute Table dialog box. Two example actions are shown below: • konqueror http://www.google.com/search?q=%nam • konqueror http://www.google.com/search?q=%% In the first example, the web browser konqueror is invoked and passed a URL to open. The URL performs a Google search on the value of the nam field from our vector layer. Note that the application or script called by the action must be in the path, or you must provide the full path. To be certain, we could rewrite the first example as: /opt/kde3/bin/konqueror http://www.google.com/search?q=%nam. This will ensure that the konqueror application will be executed when the action is invoked. The second example uses the %% notation, which does not rely on a particular field for its value. When the action is invoked, the %% will be replaced by the value of the selected field in the identify results or attribute table. Using Actions Actions can be invoked from either the Identify Results dialog, an Attribute Table dialog or from Run Fea- ture Action (recall that these dialogs can be opened by clicking Identify Features or Open Attribute Table or Run Feature Action). To invoke an action, right click on the record and choose the action from the pop-up menu. Ac- tions are listed in the popup menu by the name you assigned when defining the action. Click on the action you wish to invoke. If you are invoking an action that uses the %% notation, right-click on the field value in the Identify Results dialog or the Attribute Table dialog that you wish to pass to the application or script. Here is another example that pulls data out of a vector layer and inserts it into a file using bash and the echo com- mand (so it will only work on or perhaps ). The layer in question has fields for a species name taxon_name, latitude lat and longitude long. We would like to be able to make a spatial selection of localities and export these field values to a text file for the selected record (shown in yellow in the QGIS map area). Here is the action to achieve this: bash -c "echo \"%taxon_name %lat %long\" >> /tmp/species_localities.txt" After selecting a few localities and running the action on each one, opening the output file will show something like this: Acacia mearnsii -34.0800000000 150.0800000000 Acacia mearnsii -34.9000000000 150.1200000000 100 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Acacia mearnsii -35.2200000000 149.9300000000 Acacia mearnsii -32.2700000000 150.4100000000 As an exercise, we can create an action that does a Google search on the lakes layer. First, we need to determine the URL required to perform a search on a keyword. This is easily done by just going to Google and doing a simple search, then grabbing the URL from the address bar in your browser. From this little effort, we see that the format is http://google.com/search?q=qgis, where QGIS is the search term. Armed with this information, we can proceed: 1. Make sure the lakes layer is loaded. 2. Open the Layer Properties dialog by double-clicking on the layer in the legend, or right-click and choose Properties from the pop-up menu. 3. Click on the Actions menu. 4. Enter a name for the action, for example Google Search. 5. For the action, we need to provide the name of the external program to run. In this case, we can use Firefox. If the program is not in your path, you need to provide the full path. 6. Following the name of the external application, add the URL used for doing a Google search, up to but not including the search term: http://google.com/search?q= 7. The text in the Action field should now look like this: firefox http://google.com/search?q= 8. Click on the drop-down box containing the field names for the lakes layer. It’s located just to the left of the [Insert Field] button. 9. From the drop-down box, select ‘NAMES’ and click [Insert Field]. 10. Your action text now looks like this: firefox http://google.com/search?q=%NAMES 11. To finalize the action, click the [Add to action list] button. This completes the action, and it is ready to use. The final text of the action should look like this: firefox http://google.com/search?q=%NAMES We can now use the action. Close the Layer Properties dialog and zoom in to an area of interest. Make sure the lakes layer is active and identify a lake. In the result box you’ll now see that our action is visible: Figure 12.33: Select feature and choose action 12.3. The Vector Properties Dialog 101 QGIS User Guide, Release 2.6 When we click on the action, it brings up Firefox and navigates to the URL http://www.google.com/search?q=Tustumena. It is also possible to add further attribute fields to the ac- tion. Therefore, you can add a + to the end of the action text, select another field and click on [Insert Field]. In this example, there is just no other field available that would make sense to search for. You can define multiple actions for a layer, and each will show up in the Identify Results dialog. There are all kinds of uses for actions. For example, if you have a point layer containing locations of images or photos along with a file name, you could create an action to launch a viewer to display the image. You could also use actions to launch web-based reports for an attribute field or combination of fields, specifying them in the same way we did in our Google search example. We can also make more complex examples, for instance, using Python actions. Usually, when we create an action to open a file with an external application, we can use absolute paths, or eventually relative paths. In the second case, the path is relative to the location of the external program executable file. But what about if we need to use relative paths, relative to the selected layer (a file-based one, like a shapefile or SpatiaLite)? The following code will do the trick: command = "firefox"; imagerelpath = "images_test/test_image.jpg"; layer = qgis.utils.iface.activeLayer(); import os.path; layerpath = layer.source() if layer.providerType() == ’ogr’ else (qgis.core.QgsDataSourceURI(layer.source()).database() if layer.providerType() == ’spatialite’ else None); path = os.path.dirname(str(layerpath)); image = os.path.join(path,imagerelpath); import subprocess; subprocess.Popen( [command, image ] ); We just have to remember that the action is one of type Python and the command and imagerelpath variables must be changed to fit our needs. But what about if the relative path needs to be relative to the (saved) project file? The code of the Python action would be: command="firefox"; imagerelpath="images/test_image.jpg"; projectpath=qgis.core.QgsProject.instance().fileName(); import os.path; path=os.path.dirname(str(projectpath)) if projectpath !=’’ else None; image=os.path.join(path, imagerelpath); import subprocess; subprocess.Popen( [command, image ] ); Another Python action example is the one that allows us to add new layers to the project. For instance, the following examples will add to the project respectively a vector and a raster. The names of the files to be added to the project and the names to be given to the layers are data driven (filename and layername are column names of the table of attributes of the vector where the action was created): qgis.utils.iface.addVectorLayer(’/yourpath/[%"filename"%].shp’,’[%"layername"%]’, ’ogr’) To add a raster (a TIF image in this example), it becomes: qgis.utils.iface.addRasterLayer(’/yourpath/[% "filename" %].tif’,’[% "layername" %] ’) 12.3.8 Joins Menu The Joins menu allows you to join a loaded attribute table to a loaded vector layer. After clicking , the Add vector join dialog appears. As key columns, you have to define a join layer you want to connect with the 102 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 target vector layer. Then, you have to specify the join field that is common to both the join layer and the target layer. Now you can also specify a subset of fields from the joined layer based on the checkbox Choose which fields are joined. As a result of the join, all information from the join layer and the target layer are displayed in the attribute table of the target layer as joined information. If you specified a subset of fields only these fields are displayed in the attribute table of the target layer. QGIS currently has support for joining non-spatial table formats supported by OGR (e.g., CSV, DBF and Excel), delimited text and the PostgreSQL provider (see figure_joins_1). Figure 12.34: Join an attribute table to an existing vector layer Additionally, the add vector join dialog allows you to: • Cache join layer in virtual memory • Create attribute index on the join field 12.3.9 Diagrams Menu The Diagrams menu allows you to add a graphic overlay to a vector layer (see figure_diagrams_1). The current core implementation of diagrams provides support for pie charts, text diagrams and histograms. The menu is divided into four tabs: Appearance, Size, Postion and Options. In the cases of the text diagram and pie chart, text values of different data columns are displayed one below the other with a circle or a box and dividers. In the Size tab, diagram size is based on a fixed size or on linear scaling according to a classification attribute. The placement of the diagrams, which is done in the Position tab, interacts with the new labeling, so position conflicts between diagrams and labels are detected and solved. In addition, chart positions can be fixed manually. We will demonstrate an example and overlay on the Alaska boundary layer a text diagram showing temperature data from a climate vector layer. Both vector layers are part of the QGIS sample dataset (see section Sample Data). 12.3. The Vector Properties Dialog 103 QGIS User Guide, Release 2.6 Figure 12.35: Vector properties dialog with diagram menu 1. First, click on the Load Vector icon, browse to the QGIS sample dataset folder, and load the two vector shape layers alaska.shp and climate.shp. 2. Double click the climate layer in the map legend to open the Layer Properties dialog. 3. Click on the Diagrams menu, activate Display diagrams, and from the Diagram type combo box, select ‘Text diagram’. 4. In the Appearance tab, we choose a light blue as background color, and in the Size tab, we set a fixed size to 18 mm. 5. In the Position tab, placement could be set to ‘Around Point’. 6. In the diagram, we want to display the values of the three columns T_F_JAN, T_F_JUL and T_F_MEAN. First select T_F_JAN as Attributes and click the button, then T_F_JUL, and finally T_F_MEAN. 7. Now click [Apply] to display the diagram in the QGIS main window. 8. You can adapt the chart size in the Size tab. Deactivate the Fixed size and set the size of the diagrams on the basis of an attribute with the [Find maximum value] button and the Size menu. If the diagrams appear too small on the screen, you can activate the Increase size of small diagrams checkbox and define the minimum size of the diagrams. 9. Change the attribute colors by double clicking on the color values in the Assigned attributes field. Fig- ure_diagrams_2 gives an idea of the result. 10. Finally, click [Ok]. Remember that in the Position tab, a Data defined position of the diagrams is possible. Here, you can use attributes to define the position of the diagram. You can also set a scale-dependent visibility in the Appearance tab. 104 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.36: Diagram from temperature data overlayed on a map The size and the attributes can also be an expression. Use the button to add an expression. See Expressions chapter for more information and example. 12.3.10 Metadata Menu The Metadata menu consists of Description, Attribution, MetadataURL and Properties sections. In the Properties section, you get general information about the layer, including specifics about the type and location, number of features, feature type, and editing capabilities. The Extents table provides you with layer extent information and the Layer Spatial Reference System, which is information about the CRS of the layer. This is a quick way to get information about the layer. Additionally, you can add or edit a title and abstract for the layer in the Description section. It’s also possible to define a Keyword list here. These keyword lists can be used in a metadata catalogue. If you want to use a title from an XML metadata file, you have to fill in a link in the DataUrl field. Use Attribution to get attribute data from an XML metadata catalogue. In MetadataUrl, you can define the general path to the XML metadata catalogue. This information will be saved in the QGIS project file for subsequent sessions and will be used for QGIS server. . 12.4 Expressions The Expressions feature are available through the field calculator or the add a new column button in the attribut table or the Field tab in the Layer properties ; through the graduaded, categorized and rule-based rendering in the Style tab of the Layer properties ; through the expression-based labeling in the Labeling core application ; through the feature selection and through the diagram tab of the Layer properties. There are powerful way to manipulate attribute value in order to dynamicly change the final value in order to change the geometry style, the content of the label, the value for diagram, select some feature or create virtual column. 12.4.1 Functions List The Function List contains functions as well as fields and values. View the help function in the Selected Func- tion Help. In Expression you see the calculation expressions you create with the Function List. For the most 12.4. Expressions 105 QGIS User Guide, Release 2.6 Figure 12.37: Metadata menu in vector layers properties dialog commonly used operators, see Operators. In the Function List, click on Fields and Values to view all attributes of the attribute table to be searched. To add an attribute to the Field calculator Expression field, double click its name in the Fields and Values list. Generally, you can use the various fields, values and functions to construct the calculation expression, or you can just type it into the box. To display the values of a field, you just right click on the appropriate field. You can choose between Load top 10 unique values and Load all unique values. On the right side, the Field Values list opens with the unique values. To add a value to the Field calculator Expression box, double click its name in the Field Values list. The Operators, Math, Conversions, String, Geometry and Record groups provide several functions. In Operators, you find mathematical operators. Look in Math for mathematical functions. The Conversions group contains functions that convert one data type to another. The String group provides functions for data strings. In the Geometry group, you find functions for geometry objects. With Record group functions, you can add a numeration to your data set. To add a function to the Field calculator Expression box, click on the > and then double click the function. Operators This group contains operators (e.g., +, -, *). a + b a plus b a - b a minus b a * b a multiplied by b a / b a divided by b a % b a modulo b (for example, 7 % 2 = 1, or 2 fits into 7 three times with remainder 1) a ^ b a power b (for example, 2^2=4 or 2^3=8) a = b a and b are equal a > b a is larger than b a < b a is smaller than b a <> b a and b are not equal a != b a and b are not equal 106 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 a <= b a is less than or equal to b a >= b a is larger than or equal to b a ~ b a matches the regular expression b + a positive sign - a negative value of a || joins two values together into a string ’Hello’ || ’ world’ LIKE returns 1 if the string matches the supplied pattern ILIKE returns 1 if the string matches case-insensitive the supplied pattern (ILIKE can be used instead of LIKE to make the match case-insensitive) IS returns 1 if a is the same as b OR returns 1 when condition a or b is true AND returns 1 when condition a and b are true NOT returns 1 if a is not the same as b column name "column name" value of the field column name, take care to not be confused with simple quote, see below ’string’ a string value, take care to not be confused with double quote, see above NULL null value a IS NULL a has no value a IS NOT NULL a has a value a IN (value[,value]) a is below the values listed a NOT IN (value[,value]) a is not below the values listed Some example: • Joins a string and a value from a column name: ’My feature’s id is: ’ || "gid" • Test if the “description” attribute field starts with the ‘Hello’ string in the value (note the position of the % caracter): "description" LIKE ’Hello%’ Conditionals This group contains functions to handle conditional checks in expressions. CASE evaluates multiple expressions and returns a result CASE ELSE evaluates multiple expressions and returns a result coalesce returns the first non-NULL value from the expression list regexp_match returns true if any part of a string matches the supplied regular expression Some example: • Send back a value if the first condition is true, else another value: CASE WHEN "software" LIKE ’%QGIS%’ THEN ’QGIS’ ELSE ’Other’ Mathematical Functions This group contains math functions (e.g., square root, sin and cos). sqrt(a) square root of a abs returns the absolute value of a number sin(a) sine of a 12.4. Expressions 107 QGIS User Guide, Release 2.6 cos(a) cosine of a tan(a) tangent of a asin(a) arcsin of a acos(a) arccos of a atan(a) arctan of a atan2(y,x) arctan of y/x using the signs of the two arguments to determine the quadrant of the result exp exponential of a value ln value of the natural logarithm of the passed expression log10 value of the base 10 logarithm of the passed expression log value of the logarithm of the passed value and base round round to number of decimal places rand random integer within the range specified by the minimum and maximum argument (inclusive) randf random float within the range specified by the minimum and maximum argument (inclusive) max largest value in a set of values min smallest value in a set of values clamp restricts an input value to a specified range scale_linear transforms a given value from an input domain to an output range using linear interpolation scale_exp transforms a given value from an input domain to an output range using an exponential curve floor rounds a number downwards ceil rounds a number upwards $pi pi as value for calculations Conversions This group contains functions to convert one data type to another (e.g., string to integer, integer to string). toint converts a string to integer number toreal converts a string to real number tostring converts number to string todatetime converts a string into Qt data time type todate converts a string into Qt data type totime converts a string into Qt time type tointerval converts a string to an interval type (can be used to take days, hours, months, etc. off a date) Date and Time Functions This group contains functions for handling date and time data. $now current date and time age difference between two dates year extract the year part from a date, or the number of years from an interval month extract the month part from a date, or the number of months from an interval 108 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 week extract the week number from a date, or the number of weeks from an interval day extract the day from a date, or the number of days from an interval hour extract the hour from a datetime or time, or the number of hours from an interval minute extract the minute from a datetime or time, or the number of minutes from an interval second extract the second from a datetime or time, or the number of minutes from an interval Some example: • Get the month and the year of today in the format “10/2014” month($now) || ’/’ || year($now) String Functions This group contains functions that operate on strings (e.g., that replace, convert to upper case). lower convert string a to lower case upper convert string a to upper case title converts all words of a string to title case (all words lower case with leading capital letter) trim removes all leading and trailing white space (spaces, tabs, etc.) from a string wordwrap returns a string wrapped to a maximum/ minimum number of characters length length of string a replace returns a string with the supplied string replaced regexp_replace(a,this,that) returns a string with the supplied regular expression replaced regexp_substr returns the portion of a string which matches a supplied regular expression substr(*a*,from,len) returns a part of a string concat concatenates several strings to one strpos returns the index of a regular expression in a string left returns a substring that contains the n leftmost characters of the string right returns a substring that contains the n rightmost characters of the string rpad returns a string with supplied width padded using the fill character lpad returns a string with supplied width padded using the fill character format formats a string using supplied arguments format_number returns a number formatted with the locale separator for thousands (also truncates the number to the number of supplied places) format_date formats a date type or string into a custom string format Color Functions This group contains functions for manipulating colors. 12.4. Expressions 109 QGIS User Guide, Release 2.6 color_rgb returns a string representation of a color based on its red, green, and blue components color_rgba returns a string representation of a color based on its red, green, blue, and alpha (transparency) components ramp_color returns a string representing a color from a color ramp color_hsl returns a string representation of a color based on its hue, saturation, and lightness attributes color_hsla returns a string representation of a color based on its hue, saturation, lightness and alpha (transparency) attributes color_hsv returns a string representation of a color based on its hue, saturation, and value attributes color_hsva returns a string representation of a color based on its hue, saturation, value and alpha (transparency) attributes color_cmyk returns a string representation of a color based on its cyan, magenta, yellow and black components color_cmyka returns a string representation of a color based on its cyan, magenta, yellow, black and alpha (transparency) components Geometry Functions This group contains functions that operate on geometry objects (e.g., length, area). $geometry returns the geometry of the current feature (can be used for processing with other functions) $area returns the area size of the current feature $length returns the length size of the current feature $perimeter returns the perimeter length of the current feature $x returns the x coordinate of the current feature $y returns the y coordinate of the current feature xat retrieves the nth x coordinate of the current feature. n given as a parameter of the function yat retrieves the nth y coordinate of the current feature. n given as a parameter of the function xmin returns the minimum x coordinate of a geometry. Calculations are in the Spatial Reference System of this Geometry xmax returns the maximum x coordinate of a geometry. Calculations are in the Spatial Reference System of this Geometry ymin returns the minimum y coordinate of a geometry. Calculations are in the Spatial Reference System of this Geometry ymax returns the maximum y coordinate of a geometry. Calculations are in the Spatial Reference System of this Geometry geomFromWKT returns a geometry created from a well-known text (WKT) representation geomFromGML returns a geometry from a GML representation of geometry bbox disjoint returns 1 if the geometries do not share any space together intersects returns 1 if the geometries spatially intersect (share any portion of space) and 0 if they don’t touches returns 1 if the geometries have at least one point in common, but their interiors do not intersect crosses returns 1 if the supplied geometries have some, but not all, interior points in common contains returns true if and only if no points of b lie in the exterior of a, and at least one point of the interior of b lies in the interior of a 110 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 overlaps returns 1 if the geometries share space, are of the same dimension, but are not completely contained by each other within returns 1 if geometry a is completely inside geometry b buffer returns a geometry that represents all points whose distance from this geometry is less than or equal to distance centroid returns the geometric center of a geometry bounds returns a geometry which represents the bounding box of an input geometry. Calculations are in the Spatial Reference System of this Geometry. bounds_width returns the width of the bounding box of a geometry. Calculations are in the Spatial Reference System of this Geometry. bounds_height returns the height of the bounding box of a geometry. Calculations are in the Spatial Reference System of this Geometry. convexHull returns the convex hull of a geometry (this represents the minimum convex geometry that encloses all geometries within the set) difference returns a geometry that represents that part of geometry a that does not intersect with geometry b distance returns the minimum distance (based on spatial ref) between two geometries in projected units intersection returns a geometry that represents the shared portion of geometry a and geometry b symDifference returns a geometry that represents the portions of a and b that do not intersect combine returns the combination of geometry a and geometry b union returns a geometry that represents the point set union of the geometries geomToWKT returns the well-known text (WKT) representation of the geometry without SRID metadata Record Functions This group contains functions that operate on record identifiers. $rownum returns the number of the current row $id returns the feature id of the current row $currentfeature returns the current feature being evaluated. This can be used with the ’attribute’ function to evaluate attribute values from the current feature. $scale returns the current scale of the map canvas $uuid generates a Universally Unique Identifier (UUID) for each row. Each UUID is 38 characters long. getFeature returns the first feature of a layer matching a given attribute value. attribute returns the value of a specified attribute from a feature. $map returns the id of the current map item if the map is being drawn in a composition, or "canvas" if the map is being drawn within the main QGIS window. Fields and Values Contains a list of fields from the layer. Sample values can also be accessed via right-click. 12.4. Expressions 111 QGIS User Guide, Release 2.6 Select the field name from the list, then right-click to access a context menu with options to load sample values from the selected field. Fields name should be double-quoted. Values or string should be simple-quoted. . 12.5 Editing QGIS supports various capabilities for editing OGR, SpatiaLite, PostGIS, MSSQL Spatial and Oracle Spatial vector layers and tables. Note: The procedure for editing GRASS layers is different - see section Digitizing and editing a GRASS vector layer for details. Tip: Concurrent Edits This version of QGIS does not track if somebody else is editing a feature at the same time as you are. The last person to save their edits wins. 12.5.1 Setting the Snapping Tolerance and Search Radius Before we can edit vertices, we must set the snapping tolerance and search radius to a value that allows us an optimal editing of the vector layer geometries. Snapping tolerance Snapping tolerance is the distance QGIS uses to search for the closest vertex and/or segment you are trying to connect to when you set a new vertex or move an existing vertex. If you aren’t within the snapping tolerance, QGIS will leave the vertex where you release the mouse button, instead of snapping it to an existing vertex and/or segment. The snapping tolerance setting affects all tools that work with tolerance. 1. A general, project-wide snapping tolerance can be defined by choosing Settings → Options. On Mac, go to QGIS → Preferences.... On Linux: Edit → Options. In the Digitizing tab, you can select between ‘to vertex’, ‘to segment’ or ‘to vertex and segment’ as default snap mode. You can also define a default snapping tolerance and a search radius for vertex edits. The tolerance can be set either in map units or in pixels. The advantage of choosing pixels is that the snapping tolerance doesn’t have to be changed after zoom operations. In our small digitizing project (working with the Alaska dataset), we define the snapping units in feet. Your results may vary, but something on the order of 300 ft at a scale of 1:10000 should be a reasonable setting. 2. A layer-based snapping tolerance can be defined by choosing Settings → (or File →) Snapping options... to enable and adjust snapping mode and tolerance on a layer basis (see figure_edit_1). Note that this layer-based snapping overrides the global snapping option set in the Digitizing tab. So, if you need to edit one layer and snap its vertices to another layer, then enable snapping only on the snap to layer, then decrease the global snapping tolerance to a smaller value. Furthermore, snapping will never occur to a layer that is not checked in the snapping options dialog, regardless of the global snapping tolerance. So be sure to mark the checkbox for those layers that you need to snap to. Search radius Search radius is the distance QGIS uses to search for the closest vertex you are trying to move when you click on the map. If you aren’t within the search radius, QGIS won’t find and select any vertex for editing, and it will pop up an annoying warning to that effect. Snap tolerance and search radius are set in map units or pixels, so you may find you need to experiment to get them set right. If you specify too big of a tolerance, QGIS may snap to the 112 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.38: Edit snapping options on a layer basis wrong vertex, especially if you are dealing with a large number of vertices in close proximity. Set search radius too small, and it won’t find anything to move. The search radius for vertex edits in layer units can be defined in the Digitizing tab under Settings → Options. This is the same place where you define the general, project- wide snapping tolerance. 12.5.2 Zooming and Panning Before editing a layer, you should zoom in to your area of interest. This avoids waiting while all the vertex markers are rendered across the entire layer. Apart from using the pan and zoom-in / zoom-out icons on the toolbar with the mouse, navigating can also be done with the mouse wheel, spacebar and the arrow keys. Zooming and panning with the mouse wheel While digitizing, you can press the mouse wheel to pan inside of the main window, and you can roll the mouse wheel to zoom in and out on the map. For zooming, place the mouse cursor inside the map area and roll it forward (away from you) to zoom in and backwards (towards you) to zoom out. The mouse cursor position will be the center of the zoomed area of interest. You can customize the behavior of the mouse wheel zoom using the Map tools tab under the Settings → Options menu. Panning with the arrow keys Panning the map during digitizing is possible with the arrow keys. Place the mouse cursor inside the map area, and click on the right arrow key to pan east, left arrow key to pan west, up arrow key to pan north, and down arrow key to pan south. You can also use the space bar to temporarily cause mouse movements to pan the map. The PgUp and PgDown keys on your keyboard will cause the map display to zoom in or out without interrupting your digitizing session. 12.5.3 Topological editing Besides layer-based snapping options, you can also define topological functionalities in the Snapping options... dialog in the Settings (or File) menu. Here, you can define Enable topological editing, and/or for polygon layers, you can activate the column Avoid Int., which avoids intersection of new polygons. 12.5. Editing 113 QGIS User Guide, Release 2.6 Enable topological editing The option Enable topological editing is for editing and maintaining common boundaries in polygon mosaics. QGIS ‘detects’ a shared boundary in a polygon mosaic, so you only have to move the vertex once, and QGIS will take care of updating the other boundary. Avoid intersections of new polygons The second topological option in the Avoid Int. column, called Avoid intersections of new polygons, avoids overlaps in polygon mosaics. It is for quicker digitizing of adjacent polygons. If you already have one polygon, it is possible with this option to digitize the second one such that both intersect, and QGIS then cuts the second polygon to the common boundary. The advantage is that you don’t have to digitize all vertices of the common boundary. Enable snapping on intersections Another option is to use Enable snapping on intersection. It allows you to snap on an intersection of back- ground layers, even if there’s no vertex on the intersection. 12.5.4 Digitizing an existing layer By default, QGIS loads layers read-only. This is a safeguard to avoid accidentally editing a layer if there is a slip of the mouse. However, you can choose to edit any layer as long as the data provider supports it, and the underlying data source is writable (i.e., its files are not read-only). In general, tools for editing vector layers are divided into a digitizing and an advanced digitiz- ing toolbar, described in section Advanced digitizing. You can select and unselect both under View → Toolbars →. Using the basic digitizing tools, you can perform the following functions: Icon Purpose Icon Purpose Current edits Toggle editing Adding Features: Capture Point Adding Features: Capture Line Adding Features: Capture Polygon Move Feature Node Tool Delete Selected Cut Features Copy Features Paste Features Save layer edits Table Editing: Vector layer basic editing toolbar All editing sessions start by choosing the Toggle editing option. This can be found in the context menu after right clicking on the legend entry for a given layer. Alternatively, you can use the Toggle Editing Toggle editing button from the digitizing toolbar to start or stop the editing mode. Once the layer is in edit mode, markers will appear at the vertices, and additional tool buttons on the editing toolbar will become available. Tip: Save Regularly Remember to Save Layer Edits regularly. This will also check that your data source can accept all the changes. 114 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Adding Features You can use the Add Feature, Add Feature or Add Feature icons on the toolbar to put the QGIS cursor into digitizing mode. For each feature, you first digitize the geometry, then enter its attributes. To digitize the geometry, left-click on the map area to create the first point of your new feature. For lines and polygons, keep on left-clicking for each additional point you wish to capture. When you have finished adding points, right-click anywhere on the map area to confirm you have finished entering the geometry of that feature. The attribute window will appear, allowing you to enter the information for the new feature. Figure_edit_2 shows setting attributes for a fictitious new river in Alaska. In the Digitizing menu under the Settings → Options menu, you can also activate Suppress attributes pop-up windows after each created feature and Reuse last entered attribute values. Figure 12.39: Enter Attribute Values Dialog after digitizing a new vector feature With the Move Feature(s) icon on the toolbar, you can move existing features. Tip: Attribute Value Types For editing, the attribute types are validated during entry. Because of this, it is not possible to enter a number into a text column in the dialog Enter Attribute Values or vice versa. If you need to do so, you should edit the attributes in a second step within the Attribute table dialog. Current Edits This feature allows the digitization of multiple layers. Choose Save for Selected Layers to save all changes you made in multiple layers. You also have the opportunity to Rollback for Selected Layers, so that the digitization may be withdrawn for all selected layers. If you want to stop editing the selected layers, Cancel for Selected Layer(s) is an easy way. The same functions are available for editing all layers of the project. Node Tool For shapefile-based layers as well as SpatialLite, PostgreSQL/PostGIS, MSSQL Spatial, and Oracle Spatial tables, the Node Tool provides manipulation capabilities of feature vertices similar to CAD programs. It is possible to simply select multiple vertices at once and to move, add or delete them altogether. The node tool also works with ‘on the fly’ projection turned on, and it supports the topological editing feature. This tool is, unlike other tools in QGIS, persistent, so when some operation is done, selection stays active for this feature and tool. If the node tool is unable to find any features, a warning will be displayed. 12.5. Editing 115 QGIS User Guide, Release 2.6 It is important to set the property Settings → Options → Digitizing → Search Radius: to a number greater than zero (i.e., 10). Otherwise, QGIS will not be able to tell which vertex is being edited. Tip: Vertex Markers The current version of QGIS supports three kinds of vertex markers: ‘Semi-transparent circle’, ‘Cross’ and ‘None’. To change the marker style, choose Options from the Settings menu, click on the Digitizing tab and select the appropriate entry. Basic operations Start by activating the Node Tool and selecting a feature by clicking on it. Red boxes will appear at each vertex of this feature. • Selecting vertices: You can select vertices by clicking on them one at a time, by clicking on an edge to select the vertices at both ends, or by clicking and dragging a rectangle around some vertices. When a vertex is selected, its color changes to blue. To add more vertices to the current selection, hold down the Ctrl key while clicking. Hold down Ctrl or Shift when clicking to toggle the selection state of vertices (vertices that are currently unselected will be selected as usual, but also vertices that are already selected will become unselected). • Adding vertices: To add a vertex, simply double click near an edge and a new vertex will appear on the edge near to the cursor. Note that the vertex will appear on the edge, not at the cursor position; therefore, it should be moved if necessary. • Deleting vertices: After selecting vertices for deletion, click the Delete key. Note that you cannot use the Node Tool to delete a complete feature; QGIS will ensure it retains the minimum number of vertices for the feature type you are working on. To delete a complete feature use the Delete Selected tool. • Moving vertices: Select all the vertices you want to move. Click on a selected vertex or edge and drag in the direction you wish to move. All the selected vertices will move together. If snapping is enabled, the whole selection can jump to the nearest vertex or line. Each change made with the node tool is stored as a separate entry in the Undo dialog. Remember that all operations support topological editing when this is turned on. On-the-fly projection is also supported, and the node tool provides tooltips to identify a vertex by hovering the pointer over it. Cutting, Copying and Pasting Features Selected features can be cut, copied and pasted between layers in the same QGIS project, as long as destination layers are set to Toggle editing beforehand. Features can also be pasted to external applications as text. That is, the features are represented in CSV format, with the geometry data appearing in the OGC Well-Known Text (WKT) format. However, in this version of QGIS, text features from outside QGIS cannot be pasted to a layer within QGIS. When would the copy and paste function come in handy? Well, it turns out that you can edit more than one layer at a time and copy/paste features between layers. Why would we want to do this? Say we need to do some work on a new layer but only need one or two lakes, not the 5,000 on our big_lakes layer. We can create a new layer and use copy/paste to plop the needed lakes into it. As an example, we will copy some lakes to a new layer: 1. Load the layer you want to copy from (source layer) 2. Load or create the layer you want to copy to (target layer) 3. Start editing for target layer 4. Make the source layer active by clicking on it in the legend 116 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 5. Use the Select Single Feature tool to select the feature(s) on the source layer 6. Click on the Copy Features tool 7. Make the destination layer active by clicking on it in the legend 8. Click on the Paste Features tool 9. Stop editing and save the changes What happens if the source and target layers have different schemas (field names and types are not the same)? QGIS populates what matches and ignores the rest. If you don’t care about the attributes being copied to the target layer, it doesn’t matter how you design the fields and data types. If you want to make sure everything - the feature and its attributes - gets copied, make sure the schemas match. Tip: Congruency of Pasted Features If your source and destination layers use the same projection, then the pasted features will have geometry identical to the source layer. However, if the destination layer is a different projection, then QGIS cannot guarantee the ge- ometry is identical. This is simply because there are small rounding-off errors involved when converting between projections. Deleting Selected Features If we want to delete an entire polygon, we can do that by first selecting the polygon using the regular Select Single Feature tool. You can select multiple features for deletion. Once you have the selection set, use the Delete Selected tool to delete the features. The Cut Features tool on the digitizing toolbar can also be used to delete features. This effectively deletes the feature but also places it on a “spatial clipboard”. So, we cut the feature to delete. We could then use the Paste Features tool to put it back, giving us a one-level undo capability. Cut, copy, and paste work on the currently selected features, meaning we can operate on more than one at a time. Saving Edited Layers When a layer is in editing mode, any changes remain in the memory of QGIS. Therefore, they are not commit- ted/saved immediately to the data source or disk. If you want to save edits to the current layer but want to continue editing without leaving the editing mode, you can click the Save Layer Edits button. When you turn editing mode off with Toggle editing (or quit QGIS for that matter), you are also asked if you want to save your changes or discard them. If the changes cannot be saved (e.g., disk full, or the attributes have values that are out of range), the QGIS in-memory state is preserved. This allows you to adjust your edits and try again. Tip: Data Integrity It is always a good idea to back up your data source before you start editing. While the authors of QGIS have made every effort to preserve the integrity of your data, we offer no warranty in this regard. 12.5. Editing 117 QGIS User Guide, Release 2.6 12.5.5 Advanced digitizing Icon Purpose Icon Purpose Undo Redo Rotate Feature(s) Simplify Feature Add Ring Add Part Fill Ring Delete Ring Delete Part Reshape Features Offset Curve Split Features Split Parts Merge Selected Features Merge Attributes of Selected Features Rotate Point Symbols Table Advanced Editing: Vector layer advanced editing toolbar Undo and Redo The Undo and Redo tools allows you to undo or redo vector editing operations. There is also a dockable widget, which shows all operations in the undo/redo history (see Figure_edit_3). This widget is not displayed by default; it can be displayed by right clicking on the toolbar and activating the Undo/Redo checkbox. Undo/Redo is however active, even if the widget is not displayed. Figure 12.40: Redo and Undo digitizing steps When Undo is hit, the state of all features and attributes are reverted to the state before the reverted operation happened. Changes other than normal vector editing operations (for example, changes done by a plugin), may or may not be reverted, depending on how the changes were performed. To use the undo/redo history widget, simply click to select an operation in the history list. All features will be reverted to the state they were in after the selected operation. Rotate Feature(s) Use Rotate Feature(s) to rotate one or multiple selected features in the map canvas. You first need to select the features and then press the Rotate Feature(s) icon. The centroid of the feature(s) appears and will be the rotation anchor point. If you selected multiple features, the rotation anchor point will be the common center of the features. Press and drag the left mouse button in the desired direction to rotate the selected features. It’s also possible to create a user-defined rotation anchor point around which the selected feature will rotate. Select the features to rotate and activate the Rotate Feature(s) tool. Press and hold the Ctrl button and move the mouse 118 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 pointer (without pressing the mouse button) to the place where you want the rotation anchor to be moved. Release the Ctrl button when the desired rotation anchor point is reached. Now, press and drag the left mouse button in the desired direction to rotate the selected feature(s). Simplify Feature The Simplify Feature tool allows you to reduce the number of vertices of a feature, as long as the geometry doesn’t change and geometry type is not a multi geometry. First, select a feature. It will be highlighted by a red rubber band and a slider will appear. Moving the slider, the red rubber band will change its shape to show how the feature is being simplified. Click [OK] to store the new, simplified geometry. If a feature cannot be simplified (e.g. multi-polygons), a message will appear. Add Ring You can create ring polygons using the Add Ring icon in the toolbar. This means that inside an existing area, it is possible to digitize further polygons that will occur as a ‘hole’, so only the area between the boundaries of the outer and inner polygons remains as a ring polygon. Add Part You can add part polygons to a selected multipolygon. The new part polygon must be digitized outside the selected multi-polygon. Fill Ring You can use the Fill Ring function to add a ring to a polygon and add a new feature to the layer at the same time. Thus you need not first use the Add Ring icon and then the Add feature function anymore. Delete Ring The Delete Ring tool allows you to delete ring polygons inside an existing area. This tool only works with polygon layers. It doesn’t change anything when it is used on the outer ring of the polygon. This tool can be used on polygon and multi-polygon features. Before you select the vertices of a ring, adjust the vertex edit tolerance. Delete Part The Delete Part tool allows you to delete parts from multifeatures (e.g., to delete polygons from a multi-polygon feature). It won’t delete the last part of the feature; this last part will stay untouched. This tool works with all multi-part geometries: point, line and polygon. Before you select the vertices of a part, adjust the vertex edit tolerance. Reshape Features You can reshape line and polygon features using the Reshape Features icon on the toolbar. It replaces the line or polygon part from the first to the last intersection with the original line. With polygons, this can sometimes lead 12.5. Editing 119 QGIS User Guide, Release 2.6 to unintended results. It is mainly useful to replace smaller parts of a polygon, not for major overhauls, and the reshape line is not allowed to cross several polygon rings, as this would generate an invalid polygon. For example, you can edit the boundary of a polygon with this tool. First, click in the inner area of the polygon next to the point where you want to add a new vertex. Then, cross the boundary and add the vertices outside the polygon. To finish, right-click in the inner area of the polygon. The tool will automatically add a node where the new line crosses the border. It is also possible to remove part of the area from the polygon, starting the new line outside the polygon, adding vertices inside, and ending the line outside the polygon with a right click. Note: The reshape tool may alter the starting position of a polygon ring or a closed line. So, the point that is represented ‘twice’ will not be the same any more. This may not be a problem for most applications, but it is something to consider. Offset Curves The Offset Curve tool creates parallel shifts of line layers. The tool can be applied to the edited layer (the geometries are modified) or also to background layers (in which case it creates copies of the lines / rings and adds them to the the edited layer). It is thus ideally suited for the creation of distance line layers. The displacement is shown at the bottom left of the taskbar. To create a shift of a line layer, you must first go into editing mode and then select the feature. You can make the Offset Curve tool active and drag the cross to the desired distance. Your changes may then be saved with the Save Layer Edits tool. QGIS options dialog (Digitizing tab then Curve offset tools section) allows you to configure some parameters like Join style, Quadrant segments, Miter limit. Split Features You can split features using the Split Features icon on the toolbar. Just draw a line across the feature you want to split. Split parts In QGIS 2.0 it is now possible to split the parts of a multi part feature so that the number of parts is increased. Just draw a line across the part you want to split using the Split Parts icon. Merge selected features The Merge Selected Features tool allows you to merge features that have common boundaries. A new dialog will allow you to choose which value to choose between each selected features or select a fonction (Minimum, Maxi- mum, Median, Sum, Skip Attribute) to use for each column. Merge attributes of selected features The Merge Attributes of Selected Features tool allows you to merge attributes of features with common boundaries and attributes without merging their boundaries. First, select several features at once. Then press the Merge Attributes of Selected Features button. Now QGIS asks you which attributes are to be applied to all selected objects. As a result, all selected objects have the same attribute entries. 120 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Rotate Point Symbols Rotate Point Symbols allows you to change the rotation of point symbols in the map canvas. You must first define a rotation column from the attribute table of the point layer in the Advanced menu of the Style menu of the Layer Properties. Also, you will need to go into the ‘SVG marker’ and choose Data defined properties .... Activate Angle and choose ‘rotation’ as field. Without these settings, the tool is inactive. Figure 12.41: Rotate Point Symbols To change the rotation, select a point feature in the map canvas and rotate it, holding the left mouse button pressed. A red arrow with the rotation value will be visualized (see Figure_edit_4). When you release the left mouse button again, the value will be updated in the attribute table. Note: If you hold the Ctrl key pressed, the rotation will be done in 15 degree steps. 12.5.6 Creating new Vector layers QGIS allows you to create new shapefile layers, new SpatiaLite layers, and new GPX layers. Creation of a new GRASS layer is supported within the GRASS plugin. Please refer to section Creating a new GRASS vector layer for more information on creating GRASS vector layers. Creating a new Shapefile layer To create a new shape layer for editing, choose New → New Shapefile Layer... from the Layer menu. The New Vector Layer dialog will be displayed as shown in Figure_edit_5. Choose the type of layer (point, line or polygon) and the CRS (coordinate reference system). Note that QGIS does not yet support creation of 2.5D features (i.e., features with X,Y,Z coordinates). To complete the creation of the new shapefile layer, add the desired attributes by clicking on the [Add to attributes list] button and specifying a name and type for the attribute. A first ‘id’ column is added as default but can be removed, if not wanted. Only Type: real , Type: integer , Type: string and Type:date attributes are supported. Additionally and according to the attribute type, you can also define the width and precision of the new attribute column. Once you are happy with the attributes, click [OK] and provide a name for the shapefile. QGIS will automatically add a .shp extension to the name you specify. Once the layer has been created, it will be added to the map, and you can edit it in the same way as described in section Digitizing an existing layer above. 12.5. Editing 121 QGIS User Guide, Release 2.6 Figure 12.42: Creating a new Shapefile layer Dialog Creating a new SpatiaLite layer To create a new SpatiaLite layer for editing, choose New → New SpatiaLite Layer... from the Layer menu. The New SpatiaLite Layer dialog will be displayed as shown in Figure_edit_6. The first step is to select an existing SpatiaLite database or to create a new SpatiaLite database. This can be done with the browse button to the right of the database field. Then, add a name for the new layer, define the layer type, and specify the coordinate reference system with [Specify CRS]. If desired, you can select Create an autoincrementing primary key. To define an attribute table for the new SpatiaLite layer, add the names of the attribute columns you want to create with the corresponding column type, and click on the [Add to attribute list] button. Once you are happy with the attributes, click [OK]. QGIS will automatically add the new layer to the legend, and you can edit it in the same way as described in section Digitizing an existing layer above. Further management of SpatiaLite layers can be done with the DB Manager. See DB Manager Plugin. Creating a new GPX layer To create a new GPX file, you need to load the GPS plugin first. Plugins → Plugin Manager... opens the Plugin Manager Dialog. Activate the GPS Tools checkbox. When this plugin is loaded, choose New → Create new GPX Layer... from the Layer menu. In the Save new GPX file as dialog, you can choose where to save the new GPX layer. 122 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.43: Creating a New SpatiaLite layer Dialog 12.5. Editing 123 QGIS User Guide, Release 2.6 12.5.7 Working with the Attribute Table The attribute table displays features of a selected layer. Each row in the table represents one map feature, and each column contains a particular piece of information about the feature. Features in the table can be searched, selected, moved or even edited. To open the attribute table for a vector layer, make the layer active by clicking on it in the map legend area. Then, from the main Layer menu, choose Open Attribute Table. It is also possible to right click on the layer and choose Open Attribute Table from the drop-down menu, and to click on the Open Attribute Table button in the Attributes toolbar. This will open a new window that displays the feature attributes for the layer (figure_attributes_1). The number of features and the number of selected features are shown in the attribute table title. Figure 12.44: Attribute Table for regions layer Selecting features in an attribute table Each selected row in the attribute table displays the attributes of a selected feature in the layer. If the set of features selected in the main window is changed, the selection is also updated in the attribute table. Likewise, if the set of rows selected in the attribute table is changed, the set of features selected in the main window will be updated. Rows can be selected by clicking on the row number on the left side of the row. Multiple rows can be marked by holding the Ctrl key. A continuous selection can be made by holding the Shift key and clicking on several row headers on the left side of the rows. All rows between the current cursor position and the clicked row are selected. Moving the cursor position in the attribute table, by clicking a cell in the table, does not change the row selection. Changing the selection in the main canvas does not move the cursor position in the attribute table. The table can be sorted by any column, by clicking on the column header. A small arrow indicates the sort order (downward pointing means descending values from the top row down, upward pointing means ascending values from the top row down). For a simple search by attributes on only one column, choose the Column filter → from the menu in the bottom left corner. Select the field (column) on which the search should be performed from the drop-down menu, and hit the [Apply] button. Then, only the matching features are shown in the attribute table. To make a selection, you have to use the Select features using an Expression icon on top of the attribute table. Select features using an Expression allows you to define a subset of a table using a Function List like in the Field Calculator (see Field Calculator). The query result can then be saved as a new vector layer. For example, if you want to find regions that are boroughs from regions.shp of the QGIS sample data, you have to open the Fields and Values 124 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 menu and choose the field that you want to query. Double-click the field ‘TYPE_2’ and also [Load all unique values] . From the list, choose and double-click ‘Borough’. In the Expression field, the following query appears: "TYPE_2"=’Borough’ Here you can also use the Function list → Recent (Selection) to make a selection that you used before. The expression builder remembers the last 20 used expressions. The matching rows will be selected, and the total number of matching rows will appear in the title bar of the attribute table, as well as in the status bar of the main window. For searches that display only selected features on the map, use the Query Builder described in section Query Builder. To show selected records only, use Show Selected Features from the menu at the bottom left. The other buttons at the top of the attribute table window provide the following functionality: • Toggle editing mode to edit single values and to enable functionalities described below (also with Ctrl+E) • Save Edits (also with Ctrl+S) • Unselect all (also with Ctrl+U) • Move selected to top (also with Ctrl+T) • Invert selection (also with Ctrl+R) • Copy selected rows to clipboard (also with Ctrl+C) • Zoom map to the selected rows (also with Ctrl+J) • Pan map to the selected rows (also with Ctrl+P) • Delete selected features (also with Ctrl+D) • New Column for PostGIS layers and for OGR layers with GDAL version >= 1.6 (also with Ctrl+W) • Delete Column for PostGIS layers and for OGR layers with GDAL version >= 1.9 (also with Ctrl+L) • Open field calculator (also with Ctrl+I) Below these buttons is the Field Calculator bar, which allows calculations to be quickly applied attributes visible in the table. This bar uses the same expressions as the Field Calculator (see Field Calculator). Tip: Skip WKT geometry If you want to use attribute data in external programs (such as Excel), use the Copy selected rows to clipboard button. You can copy the information without vector geometries if you deactivate Settings → Options → Data sources menu Copy geometry in WKT representation from attribute table. Save selected features as new layer The selected features can be saved as any OGR-supported vector format and also transformed into another coordi- nate reference system (CRS). Just open the right mouse menu of the layer and click on Save as to define the name of the output file, its format and CRS (see section Map Legend). To save the selection ensure that the Save only selected features is selected. It is also possible to specify OGR creation options within the dialog. 12.5. Editing 125 QGIS User Guide, Release 2.6 Paste into new layer Features that are on the clipboard may be pasted into a new layer. To do this, first make a layer editable. Select some features, copy them to the clipboard, and then paste them into a new layer using Edit → Paste Features as and choosing New vector layer or New memory layer. This applies to features selected and copied within QGIS and also to features from another source defined using well-known text (WKT). Working with non spatial attribute tables QGIS allows you also to load non-spatial tables. This currently includes tables supported by OGR and delimited text, as well as the PostgreSQL, MSSQL and Oracle provider. The tables can be used for field lookups or just generally browsed and edited using the table view. When you load the table, you will see it in the legend field. It can be opened with the Open Attribute Table tool and is then editable like any other layer attribute table. As an example, you can use columns of the non-spatial table to define attribute values, or a range of values that are allowed, to be added to a specific vector layer during digitizing. Have a closer look at the edit widget in section Fields Menu to find out more. 12.5.8 Creating one to many relations Relations are a technique often used in databases. The concept is, that features (rows) of different layers (tables) can belong to each other. As an example you have a layer with all regions of alaska (polygon) which provides some attributes about its name and region type and a unique id (which acts as primary key). Foreign keys Then you get another point layer or table with information about airports that are located in the regions and you also want to keep track of these. If you want to add them to the region layer, you need to create a one to many relation using foreign keys, because there are several airports in most regions. Figure 12.45: Alaska region with airports In addition to the already existing attributes in the airports attribute table another field fk_region which acts as a foreign key (if you have a database, you will probably want to define a constraint on it). 126 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 This field fk_region will always contain an id of a region. It can be seen like a pointer to the region it belongs to. And you can design a custom edit form for the editing and QGIS takes care about the setup. It works with different providers (so you can also use it with shape and csv files) and all you have to do is to tell QGIS the relations between your tables. Layers QGIS makes no difference between a table and a vector layer. Basically, a vector layer is a table with a geometry. So can add your table as a vector layer. To demostrate you can load the ‘region’ shapefile (with geometries) and the ‘airport’ csv table (without geometries) and a foreign key (fk_region) to the layer region. This means, that each airport belongs to exactly one region while each region can have any number of airports (a typical one to many relation). Definition (Relation Manager) The first thing we are going to do is to let QGIS know about the relations between the layer. This is done in Settings → Project Properties. Open the Relations menu and click on Add. • name is going to be used as a title. It should be a human readable string, describing, what the relation is used for. We will just call say “Airports” in this case. • referencing layer is the one with the foreign key field on it. In our case this is the airports layer • referencing field will say, which field points to the other layer so this is fk_region in this case • referenced layer is the one with the primary key, pointed to, so here it is the regions layer • referenced field is the primary key of the referenced layer so it is ID • id will be used for internal purposes and has to be unique. You may need it to build custom forms once this is supported. If you leave it empty, one will be generated for you but you can assign one yourself to get one that is easier to handle. Figure 12.46: Relation Manager 12.5. Editing 127 QGIS User Guide, Release 2.6 Forms Now that QGIS knows about the relation, it will be used to improve the forms it generates. As we did not change the default form method (autogenerated) it will just add a new widget in our form. So let’s select the layer region in the legend and use the identify tool. Depending on your settings, the form might open directly or you will have to choose to open it in the identification dialog under actions. Figure 12.47: Identification dialog regions with relation to airports As you can see, the airports assigned to this particular region are all shown in a table. And there are also some buttons available. Let’s review them shortly • The button is for toggling the edit mode. Be aware that it toggles the edit mode of the airport layer, although we are in the feature form of a feature from the region layer. But the table is representing features of the airport layer. • The button will add a new feature to the airport layer. And it will assign the new airport to the current region by default. • The button will delete the selected airport permanently. • The symbol will open a new dialog where you can select any existing airport which will then be assigned to the current region. This may be handy if you created the airport on the wrong region by accident. • The symbol will unlink the selected airport from the current region, leaving them unassigned (the foreign key is set to NULL) effectively. • The two buttons to the right switch between table view and form view where the later let’s you view all the airports in their respective form. If you work on the airport table, a new widget type is available which lets you embed the feature form of the referenced region on the feature form of the airports. It can be used when you open the layer properties of the airports table, switch to the Fields menu and change the widget type of the foreign key field ‘fk_region’ to Relation Reference. If you look at the feature dialog now, you will see, that the form of the region is embedded inside the airports form and will even have a combobox, which allows you to assign the current airport to another region. . 128 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.48: Identification dialog airport with relation to regions 12.6 Query Builder The Query Builder allows you to define a subset of a table using a SQL-like WHERE clause and to display the result in the main window. The query result can then be saved as a new vector layer. 12.6.1 Query Open the Query Builder by opening the Layer Properties and going to the General menu. Under Feature subset, click on the [Query Builder] button to open the Query builder. For example, if you have a regions layer with a TYPE_2 field, you could select only regions that are borough in the Provider specific filter expression box of the Query Builder. Figure_attributes_2 shows an example of the Query Builder populated with the regions.shp layer from the QGIS sample data. The Fields, Values and Operators sections help you to construct the SQL-like query. Figure 12.49: Query Builder The Fields list contains all attribute columns of the attribute table to be searched. To add an attribute column to 12.6. Query Builder 129 QGIS User Guide, Release 2.6 the SQL WHERE clause field, double click its name in the Fields list. Generally, you can use the various fields, values and operators to construct the query, or you can just type it into the SQL box. The Values list lists the values of an attribute table. To list all possible values of an attribute, select the attribute in the Fields list and click the [all] button. To list the first 25 unique values of an attribute column, select the attribute column in the Fields list and click the [Sample] button. To add a value to the SQL WHERE clause field, double click its name in the Values list. The Operators section contains all usable operators. To add an operator to the SQL WHERE clause field, click the appropriate button. Relational operators ( = , > , ...), string comparison operator (LIKE), and logical operators (AND, OR, ...) are available. The [Test] button shows a message box with the number of features satisfying the current query, which is useful in the process of query construction. The [Clear] button clears the text in the SQL WHERE clause text field. The [OK] button closes the window and selects the features satisfying the query. The [Cancel] button closes the window without changing the current selection. QGIS treats the resulting subset acts as if it where the entire layer. For example if you applied the filter above for ‘Borough’, you can not display, query, save or edit Ankorage, because that is a ‘Manicpality’ and therefore not part of the subset. The only exception is that unless your layer is part of a database, using a subset will prevent you from editing the layer. . 12.7 Field Calculator The Field Calculator button in the attribute table allows you to perform calculations on the basis of existing attribute values or defined functions, for instance, to calculate length or area of geometry features. The results can be written to a new attribute field, a virtual field, or they can be used to update values in an existing field. Tip: Virtual Fields • Virtual fields are not permanent and are not saved. • To make a field virtual it must be done when the field is made. The field calculator is now available on any layer that supports edit. When you click on the field calculator icon the dialog opens (see figure_attributes_3). If the layer is not in edit mode, a warning is displayed and using the field calculator will cause the layer to be put in edit mode before the calculation is made. The quick field calculation bar in top of the attribute table is only visible if the layer is editable. In quick field calculation bar, you first select the existing field name then open the expression dialog to create your expression or write it directly in the field then click on Update All button. In the field calculator dialog, you first must select whether you want to only update selected features, create a new attribute field where the results of the calculation will be added or update an existing field. If you choose to add a new field, you need to enter a field name, a field type (integer, real or string), the total field width, and the field precision (see figure_attributes_3). For example, if you choose a field width of 10 and a field precision of 3, it means you have 6 digits before the dot, then the dot and another 3 digits for the precision. A short example illustrates how the field calculator works. We want to calculate the length in km of the railroads layer from the QGIS sample dataset: 1. Load the shapefile railroads.shp in QGIS and press Open Attribute Table. 2. Click on Toggle editing mode and open the Field Calculator dialog. 3. Select the Create a new field checkbox to save the calculations into a new field. 130 Chapter 12. Working with Vector Data QGIS User Guide, Release 2.6 Figure 12.50: Field Calculator 12.7. Field Calculator 131 QGIS User Guide, Release 2.6 4. Add length as Output field name and real as Output field type, and define Output field width to be 10 and Precision, 3. 5. Now double click on function $length in the Geometry group to add it into the Field calculator expression box. 6. Complete the expression by typing ‘’/ 1000” in the Field calculator expression box and click [Ok]. 7. You can now find a new field length in the attribute table. The available functions are listed in Expressions chapter. . 132 Chapter 12. Working with Vector Data CHAPTER 13 Working with Raster Data . 13.1 Working with Raster Data This section describes how to visualize and set raster layer properties. QGIS uses the GDAL library to read and write raster data formats, including ArcInfo Binary Grid, ArcInfo ASCII Grid, GeoTIFF, ERDAS IMAGINE, and many more. GRASS raster support is supplied by a native QGIS data provider plugin. The raster data can also be loaded in read mode from zip and gzip archives into QGIS. As of the date of this document, more than 100 raster formats are supported by the GDAL library (see GDAL-SOFTWARE-SUITE in Literature and Web References). A complete list is available at http://www.gdal.org/formats_list.html. Note: Not all of the listed formats may work in QGIS for various reasons. For example, some require external commercial libraries, or the GDAL installation of your OS may not have been built to support the format you want to use. Only those formats that have been well tested will appear in the list of file types when loading a raster into QGIS. Other untested formats can be loaded by selecting the [GDAL] All files (*) filter. Working with GRASS raster data is described in section GRASS GIS Integration. 13.1.1 What is raster data? Raster data in GIS are matrices of discrete cells that represent features on, above or below the earth’s surface. Each cell in the raster grid is the same size, and cells are usually rectangular (in QGIS they will always be rectangular). Typical raster datasets include remote sensing data, such as aerial photography, or satellite imagery and modelled data, such as an elevation matrix. Unlike vector data, raster data typically do not have an associated database record for each cell. They are geocoded by pixel resolution and the x/y coordinate of a corner pixel of the raster layer. This allows QGIS to position the data correctly in the map canvas. QGIS makes use of georeference information inside the raster layer (e.g., GeoTiff) or in an appropriate world file to properly display the data. 13.1.2 Loading raster data in QGIS Raster layers are loaded either by clicking on the Add Raster Layer icon or by selecting the Layer → Add Raster Layer menu option. More than one layer can be loaded at the same time by holding down the Ctrl or Shift key and clicking on multiple items in the Open a GDAL Supported Raster Data Source dialog. 133 QGIS User Guide, Release 2.6 Once a raster layer is loaded in the map legend, you can click on the layer name with the right mouse button to select and activate layer-specific features or to open a dialog to set raster properties for the layer. Right mouse button menu for raster layers • Zoom to Layer Extent • Zoom to Best Scale (100%) • Stretch Using Current Extend • Show in Overview • Remove • Duplicate • Set Layer CRS • Set Project CRS from Layer • Save as ... • Properties • Rename • Copy Style • Add New Group • Expand all • Collapse all • Update Drawing Order . 13.2 Raster Properties Dialog To view and set the properties for a raster layer, double click on the layer name in the map legend, or right click on the layer name and choose Properties from the context menu. This will open the Raster Layer Properties dialog (see figure_raster_1). There are several menus in the dialog: • General • Style • Transparency • Pyramids • Histogram • Metadata 13.2.1 General Menu Layer Info The General menu displays basic information about the selected raster, including the layer source path, the display name in the legend (which can be modified), and the number of columns, rows and no-data values of the raster. 134 Chapter 13. Working with Raster Data QGIS User Guide, Release 2.6 Figure 13.1: Raster Layers Properties Dialog Coordinate reference system Here, you find the coordinate reference system (CRS) information printed as a PROJ.4 string. If this setting is not correct, it can be modified by clicking the [Specify] button. Scale Dependent visibility Additionally scale-dependent visibility can be set in this tab. You will need to check the checkbox and set an appropriate scale where your data will be displayed in the map canvas. At the bottom, you can see a thumbnail of the layer, its legend symbol, and the palette. 13.2.2 Style Menu Band rendering QGIS offers four different Render types. The renderer chosen is dependent on the data type. 1. Multiband color - if the file comes as a multiband with several bands (e.g., used with a satellite image with several bands) 2. Paletted - if a single band file comes with an indexed palette (e.g., used with a digital topographic map) 3. Singleband gray - (one band of) the image will be rendered as gray; QGIS will choose this renderer if the file has neither multibands nor an indexed palette nor a continous palette (e.g., used with a shaded relief map) 4. Singleband pseudocolor - this renderer is possible for files with a continuous palette, or color map (e.g., used with an elevation map) 13.2. Raster Properties Dialog 135 QGIS User Guide, Release 2.6 Multiband color With the multiband color renderer, three selected bands from the image will be rendered, each band representing the red, green or blue component that will be used to create a color image. You can choose several Contrast enhancement methods: ‘No enhancement’, ‘Stretch to MinMax’, ‘Stretch and clip to MinMax’ and ‘Clip to min max’. Figure 13.2: Raster Renderer - Multiband color This selection offers you a wide range of options to modify the appearance of your raster layer. First of all, you have to get the data range from your image. This can be done by choosing the Extent and pressing [Load]. QGIS can Estimate (faster) the Min and Max values of the bands or use the Actual (slower) Accuracy. Now you can scale the colors with the help of the Load min/max values section. A lot of images have a few very low and high data. These outliers can be eliminated using the Cumulative count cut setting. The standard data range is set from 2% to 98% of the data values and can be adapted manually. With this setting, the gray character of the image can disappear. With the scaling option Min/max, QGIS creates a color table with all of the data included in the original image (e.g., QGIS creates a color table with 256 values, given the fact that you have 8 bit bands). You can also calculate your color table using the Mean +/- standard deviation x . Then, only the values within the standard deviation or within multiple standard deviations are considered for the color table. This is useful when you have one or two cells with abnormally high values in a raster grid that are having a negative impact on the rendering of the raster. All calculations can also be made for the Current extent. Tip: Viewing a Single Band of a Multiband Raster If you want to view a single band of a multiband image (for example, Red), you might think you would set the Green and Blue bands to “Not Set”. But this is not the correct way. To display the Red band, set the image type to ‘Singleband gray’, then select Red as the band to use for Gray. Paletted This is the standard render option for singleband files that already include a color table, where each pixel value is assigned to a certain color. In that case, the palette is rendered automatically. If you want to change colors assigned to certain values, just double-click on the color and the Select color dialog appears. Also, in QGIS 2.2. it’s now possible to assign a label to the color values. The label appears in the legend of the raster layer then. Contrast enhancement Note: When adding GRASS rasters, the option Contrast enhancement will always be set automatically to stretch to min max, regardless of if this is set to another value in the QGIS general options. 136 Chapter 13. Working with Raster Data QGIS User Guide, Release 2.6 Figure 13.3: Raster Renderer - Paletted Singleband gray This renderer allows you to render a single band layer with a Color gradient: ‘Black to white’ or ‘White to black’. You can define a Min and a Max value by choosing the Extent first and then pressing [Load]. QGIS can Estimate (faster) the Min and Max values of the bands or use the Actual (slower) Accuracy. Figure 13.4: Raster Renderer - Singleband gray With the Load min/max values section, scaling of the color table is possible. Outliers can be eliminated using the Cumulative count cut setting. The standard data range is set from 2% to 98% of the data values and can be adapted manually. With this setting, the gray character of the image can disappear. Further settings can be made with Min/max and Mean +/- standard deviation x . While the first one creates a color table with all of the data included in the original image, the second creates a color table that only considers values within the standard deviation or within multiple standard deviations. This is useful when you have one or two cells with abnormally high values in a raster grid that are having a negative impact on the rendering of the raster. Singleband pseudocolor 13.2. Raster Properties Dialog 137 QGIS User Guide, Release 2.6 This is a render option for single-band files, including a continous palette. You can also create individual color maps for the single bands here. Three types of color interpolation are available: Figure 13.5: Raster Renderer - Singleband pseudocolor 1. Discrete 2. Linear 3. Exact In the left block, the button Add values manually adds a value to the individual color table. The button Remove selected row deletes a value from the individual color table, and the Sort colormap items button sorts the color table according to the pixel values in the value column. Double clicking on the value column lets you insert a specific value. Double clicking on the color column opens the dialog Change color, where you can select a color to apply on that value. Further, you can also add labels for each color, but this value won’t be displayed when you use the identify feature tool. You can also click on the button Load color map from band, which tries to load the table from the band (if it has any). And you can use the buttons Load color map from file or Export color map to file to load an existing color table or to save the defined color table for other sessions. In the right block, Generate new color map allows you to create newly categorized color maps. For the Classi- fication mode ‘Equal interval’, you only need to select the number of classes and press the button Classify. You can invert the colors of the color map by clicking the Invert checkbox. In the case of the Mode ‘Continous’, QGIS creates classes automatically depending on the Min and Max. Defining Min/Max values can be done with the help of the Load min/max values section. A lot of images have a few very low and high data. These outliers can be eliminated using the Cumulative count cut setting. The standard data range is set from 2% to 98% of the data values and can be adapted manually. With this setting, the gray character of the image can disappear. With the scaling option Min/max, QGIS creates a color table with all of the data included in the 138 Chapter 13. Working with Raster Data QGIS User Guide, Release 2.6 original image (e.g., QGIS creates a color table with 256 values, given the fact that you have 8 bit bands). You can also calculate your color table using the Mean +/- standard deviation x . Then, only the values within the standard deviation or within multiple standard deviations are considered for the color table. Color rendering For every Band rendering, a Color rendering is possible. You can also achieve special rendering effects for your raster file(s) using one of the blending modes (see The Vector Properties Dialog). Further settings can be made in modifiying the Brightness, the Saturation and the Contrast. You can also use a Grayscale option, where you can choose between ‘By lightness’, ‘By luminosity’ and ‘By average’. For one hue in the color table, you can modify the ‘Strength’. Resampling The Resampling option makes its appearance when you zoom in and out of an image. Resampling modes can optimize the appearance of the map. They calculate a new gray value matrix through a geometric transformation. Figure 13.6: Raster Rendering - Resampling When applying the ‘Nearest neighbour’ method, the map can have a pixelated structure when zooming in. This appearance can be improved by using the ‘Bilinear’ or ‘Cubic’ method, which cause sharp features to be blurred. The effect is a smoother image. This method can be applied, for instance, to digital topographic raster maps. 13.2.3 Transparency Menu QGIS has the ability to display each raster layer at a different transparency level. Use the transparency slider to indicate to what extent the underlying layers (if any) should be visible though the current raster layer. This is very useful if you like to overlay more than one raster layer (e.g., a shaded relief map overlayed by a classified raster map). This will make the look of the map more three dimensional. Additionally, you can enter a raster value that should be treated as NODATA in the Additional no data value menu. An even more flexible way to customize the transparency can be done in the Custom transparency options section. The transparency of every pixel can be set here. As an example, we want to set the water of our example raster file landcover.tif to a transparency of 20%. The following steps are neccessary: 13.2. Raster Properties Dialog 139 QGIS User Guide, Release 2.6 1. Load the raster file landcover.tif. 2. Open the Properties dialog by double-clicking on the raster name in the legend, or by right-clicking and choosing Properties from the pop-up menu. 3. Select the Transparency menu. 4. From the Transparency band menu, choose ‘None’. 5. Click the Add values manually button. A new row will appear in the pixel list. 6. Enter the raster value in the ‘From’ and ‘To’ column (we use 0 here), and adjust the transparency to 20%. 7. Press the [Apply] button and have a look at the map. You can repeat steps 5 and 6 to adjust more values with custom transparency. As you can see, it is quite easy to set custom transparency, but it can be quite a lot of work. Therefore, you can use the button Export to file to save your transparency list to a file. The button Import from file loads your transparency settings and applies them to the current raster layer. 13.2.4 Pyramids Menu Large resolution raster layers can slow navigation in QGIS. By creating lower resolution copies of the data (pyra- mids), performance can be considerably improved, as QGIS selects the most suitable resolution to use depending on the level of zoom. You must have write access in the directory where the original data is stored to build pyramids. Several resampling methods can be used to calculate the pyramids: • Nearest Neighbour • Average • Gauss • Cubic • Mode • None If you choose ‘Internal (if possible)’ from the Overview format menu, QGIS tries to build pyramids internally. You can also choose ‘External’ and ‘External (Erdas Imagine)’. Please note that building pyramids may alter the original data file, and once created they cannot be removed. If you wish to preserve a ‘non-pyramided’ version of your raster, make a backup copy prior to building pyramids. 13.2.5 Histogram Menu The Histogram menu allows you to view the distribution of the bands or colors in your raster. The histogram is generated automatically when you open the Histogram menu. All existing bands will be displayed together. You can save the histogram as an image with the button. With the Visibility option in the Prefs/Actions menu, you can display histograms of the individual bands. You will need to select the option Show selected band. The Min/max options allow you to ‘Always show min/max markers’, to ‘Zoom to min/max’ and to ‘Update style to min/max’. With the Actions option, you can ‘Reset’ and ‘Recompute histogram’ after you have chosen the Min/max options. 140 Chapter 13. Working with Raster Data QGIS User Guide, Release 2.6 Figure 13.7: The Pyramids Menu Figure 13.8: Raster Histogram 13.2. Raster Properties Dialog 141 QGIS User Guide, Release 2.6 13.2.6 Metadata Menu The Metadata menu displays a wealth of information about the raster layer, including statistics about each band in the current raster layer. From this menu, entries may be made for the Description, Attribution, MetadataUrl and Properties. In Properties, statistics are gathered on a ‘need to know’ basis, so it may well be that a given layer’s statistics have not yet been collected. Figure 13.9: Raster Metadata . 13.3 Raster Calculator The Raster Calculator in the Raster menu allows you to perform calculations on the basis of existing raster pixel values (see figure_raster_10). The results are written to a new raster layer with a GDAL-supported format. The Raster bands list contains all loaded raster layers that can be used. To add a raster to the raster calculator expression field, double click its name in the Fields list. You can then use the operators to construct calculation expressions, or you can just type them into the box. In the Result layer section, you will need to define an output layer. You can then define the extent of the calculation area based on an input raster layer, or based on X,Y coordinates and on columns and rows, to set the resolution of the output layer. If the input layer has a different resolution, the values will be resampled with the nearest neighbor algorithm. The Operators section contains all available operators. To add an operator to the raster calculator expression box, click the appropriate button. Mathematical calculations (+,-,*, ... ) and trigonometric functions (sin, cos, tan, ... ) are available. Stay tuned for more operators to come! With the Add result to project checkbox, the result layer will automatically be added to the legend area and can be visualized. 13.3.1 Examples Convert elevation values from meters to feet Creating an elevation raster in feet from a raster in meters, you need to use the conversion factor for meters to feet: 3.28. The expression is: 142 Chapter 13. Working with Raster Data QGIS User Guide, Release 2.6 Figure 13.10: Raster Calculator "elevation@1"* 3.28 Using a mask If you want to mask out parts of a raster – say, for instance, because you are only interested in elevations above 0 meters – you can use the following expression to create a mask and apply the result to a raster in one step. ("elevation@1">=0)*"elevation@1" In other words, for every cell greater than or equal to 0, set its value to 1. Otherwise set it to 0. This creates the mask on the fly. If you want to classify a raster – say, for instance into two elevation classes, you can use the following expression to create a raster with two values 1 and 2 in one step. ("elevation@1"< 50)* 1+("eleevation@1">= 50)* 2 In other words, for every cell less than 50 set its value to 1. For every cell greater than or equal 50 set its value to 2. . 13.3. Raster Calculator 143 QGIS User Guide, Release 2.6 144 Chapter 13. Working with Raster Data CHAPTER 14 Working with OGC Data . 14.1 QGIS as OGC Data Client The Open Geospatial Consortium (OGC) is an international organization with membership of more than 300 commercial, governmental, nonprofit and research organizations worldwide. Its members develop and implement standards for geospatial content and services, GIS data processing and exchange. Describing a basic data model for geographic features, an increasing number of specifications are developed by OGC to serve specific needs for interoperable location and geospatial technology, including GIS. Further information can be found at http://www.opengeospatial.org/. Important OGC specifications supported by QGIS are: • WMS — Web Map Service (WMS/WMTS Client) • WMTS — Web Map Tile Service (WMS/WMTS Client) • WFS — Web Feature Service (WFS and WFS-T Client) • WFS-T — Web Feature Service - Transactional (WFS and WFS-T Client) • WCS — Web Coverage Service (WCS Client) • SFS — Simple Features for SQL (PostGIS Layers) • GML — Geography Markup Language OGC services are increasingly being used to exchange geospatial data between different GIS implementations and data stores. QGIS can deal with the above specifications as a client, being SFS (through support of the PostgreSQL / PostGIS data provider, see section PostGIS Layers). 14.1.1 WMS/WMTS Client Overview of WMS Support QGIS currently can act as a WMS client that understands WMS 1.1, 1.1.1 and 1.3 servers. In particular, it has been tested against publicly accessible servers such as DEMIS. A WMS server acts upon requests by the client (e.g., QGIS) for a raster map with a given extent, set of layers, symbolization style, and transparency. The WMS server then consults its local data sources, rasterizes the map, and sends it back to the client in a raster format. For QGIS, this format would typically be JPEG or PNG. WMS is generically a REST (Representational State Transfer) service rather than a full-blown Web service. As such, you can actually take the URLs generated by QGIS and use them in a web browser to retrieve the same images that QGIS uses internally. This can be useful for troubleshooting, as there are several brands of WMS server on the market and they all have their own interpretation of the WMS standard. 145 QGIS User Guide, Release 2.6 WMS layers can be added quite simply, as long as you know the URL to access the WMS server, you have a serviceable connection to that server, and the server understands HTTP as the data transport mechanism. Overview of WMTS Support QGIS can also act as a WMTS client. WMTS is an OGC standard for distributing tile sets of geospatial data. This is a faster and more efficient way of distributing data than WMS because with WMTS, the tile sets are pre- generated, and the client only requests the transmission of the tiles, not their production. A WMS request typically involves both the generation and transmission of the data. A well-known example of a non-OGC standard for viewing tiled geospatial data is Google Maps. In order to display the data at a variety of scales close to what the user might want, the WMTS tile sets are produced at several different scale levels and are made available for the GIS client to request them. This diagram illustrates the concept of tile sets: Figure 14.1: Concept of WMTS tile sets The two types of WMTS interfaces that QGIS supports are via Key-Value-Pairs (KVP) and RESTful. These two interfaces are different, and you need to specify them to QGIS differently. 1) In order to access a WMTS KVP service, a QGIS user must open the WMS/WMTS interface and add the following string to the URL of the WMTS tile service: "?SERVICE=WMTS&REQUEST=GetCapabilities" An example of this type of address is http://opencache.statkart.no/gatekeeper/gk/gk.open_wmts?\ service=WMTS&request=GetCapabilities For testing the topo2 layer in this WMTS works nicely. Adding this string indicates that a WMTS web service is to be used instead of a WMS service. 2. The RESTful WMTS service takes a different form, a straightforward URL. The format recommended by the OGC is: {WMTSBaseURL}/1.0.0/WMTSCapabilities.xml This format helps you to recognize that it is a RESTful address. A RESTful WMTS is accessed in QGIS by simply adding its address in the WMS setup in the URL field of the form. An example of this type of address for the case of an Austrian basemap is http://maps.wien.gv.at/basemap/1.0.0/WMTSCapabilities.xml. Note: You can still find some old services called WMS-C. These services are quite similar to WMTS (i.e., same purpose but working a little bit differently). You can manage them the same as you do WMTS services. Just add ?tiled=true at the end of the url. See http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification for more information about this specification. 146 Chapter 14. Working with OGC Data QGIS User Guide, Release 2.6 When you read WMTS, you can often think WMS-C also. Selecting WMS/WMTS Servers The first time you use the WMS feature in QGIS, there are no servers defined. Begin by clicking the Add WMS layer button on the toolbar, or selecting Layer → Add WMS Layer.... The dialog Add Layer(s) from a Server for adding layers from the WMS server appears. You can add some servers to play with by clicking the [Add default servers] button. This will add two WMS demo servers for you to use: the WMS servers of the DM Solutions Group and Lizardtech. To define a new WMS server in the Layers tab, select the [New] button. Then enter the parameters to connect to your desired WMS server, as listed in table_OGC_1: Name A name for this connection. This name will be used in the Server Connections drop-down box so that you can distinguish it from other WMS servers. URL URL of the server providing the data. This must be a resolvable host name – the same format as you would use to open a telnet connection or ping a host. Username Username to access a secured WMS server. This parameter is optional. Password Password for a basic authenticated WMS server. This parameter is optional. Ignore GetMap URI Ignore GetMap URI reported in capabilities. Use given URI from URL field above. Ignore GetFeatureInfo URI Ignore GetFeatureInfo URI reported in capabilities. Use given URI from URL field above. Table OGC 1: WMS Connection Parameters If you need to set up a proxy server to be able to receive WMS services from the internet, you can add your proxy server in the options. Choose Settings → Options and click on the Network & Proxy tab. There, you can add your proxy settings and enable them by setting Use proxy for web access. Make sure that you select the correct proxy type from the Proxy type drop-down menu. Once the new WMS server connection has been created, it will be preserved for future QGIS sessions. Tip: On WMS Server URLs Be sure, when entering the WMS server URL, that you have the base URL only. For example, you shouldn’t have fragments such as request=GetCapabilities or version=1.0.0 in your URL. Loading WMS/WMTS Layers Once you have successfully filled in your parameters, you can use the [Connect] button to retrieve the capabilities of the selected server. This includes the image encoding, layers, layer styles and projections. Since this is a network operation, the speed of the response depends on the quality of your network connection to the WMS server. While downloading data from the WMS server, the download progress is visualized in the lower left of the WMS dialog. Your screen should now look a bit like figure_OGR_1, which shows the response provided by the DM Solutions Group WMS server. Image Encoding The Image encoding section lists the formats that are supported by both the client and server. Choose one depend- ing on your image accuracy requirements. Tip: Image Encoding You will typically find that a WMS server offers you the choice of JPEG or PNG image encoding. JPEG is a lossy compression format, whereas PNG faithfully reproduces the raw raster data. 14.1. QGIS as OGC Data Client 147 QGIS User Guide, Release 2.6 Figure 14.2: Dialog for adding a WMS server, showing its available layers 148 Chapter 14. Working with OGC Data QGIS User Guide, Release 2.6 Use JPEG if you expect the WMS data to be photographic in nature and/or you don’t mind some loss in picture quality. This trade-off typically reduces by five times the data transfer requirement compared with PNG. Use PNG if you want precise representations of the original data and you don’t mind the increased data transfer requirements. Options The Options area of the dialog provides a text field where you can add a Layer name for the WMS layer. This name will appear in the legend after loading the layer. Below the layer name, you can define Tile size if you want to set tile sizes (e.g., 256x256) to split up the WMS request into multiple requests. The Feature limit for GetFeatureInfo defines what features from the server to query. If you select a WMS from the list, a field with the default projection provided by the mapserver appears. If the [Change...] button is active, you can click on it and change the default projection of the WMS to another CRS provided by the WMS server. Layer Order The Layer Order tab lists the selected layers available from the current connected WMS server. You may notice that some layers are expandable; this means that the layer can be displayed in a choice of image styles. You can select several layers at once, but only one image style per layer. When several layers are selected, they will be combined at the WMS server and transmitted to QGIS in one go. Tip: WMS Layer Ordering WMS layers rendered by a server are overlaid in the order listed in the Layers section, from top to bottom of the list. If you want to change the overlay order, you can use the Layer Order tab. Transparency In this version of QGIS, the Global transparency setting from the Layer Properties is hard coded to be always on, where available. Tip: WMS Layer Transparency The availability of WMS image transparency depends on the image encoding used: PNG and GIF support trans- parency, whilst JPEG leaves it unsupported. Coordinate Reference System A coordinate reference system (CRS) is the OGC terminology for a QGIS projection. Each WMS layer can be presented in multiple CRSs, depending on the capability of the WMS server. To choose a CRS, select [Change...] and a dialog similar to Figure Projection 3 in Working with Projections will appear. The main difference with the WMS version of the dialog is that only those CRSs supported by the WMS server will be shown. Server search Within QGIS, you can search for WMS servers. Figure_OGC_2 shows the Server Search tab with the Add Layer(s) from a Server dialog. As you can see, it is possible to enter a search string in the text field and hit the [Search] button. After a short while, the search result will be populated into the list below the text field. Browse the result list and inspect your search results within the table. To visualize the results, select a table entry, press the [Add selected row to WMS list] button and change back to the Layers tab. QGIS has automatically updated your server list, and the selected search result is already enabled in the list of saved WMS servers in the Layers tab. You only need to request the list 14.1. QGIS as OGC Data Client 149 QGIS User Guide, Release 2.6 Figure 14.3: Dialog for searching WMS servers after some keywords of layers by clicking the [Connect] button. This option is quite handy when you want to search maps by specific keywords. Basically, this option is a front end to the API of http://geopole.org. Tilesets When using WMTS (Cached WMS) services like http://opencache.statkart.no/gatekeeper/gk/gk.open_wmts?\ service=WMTS&request=GetCapabilities you are able to browse through the Tilesets tab given by the server. Additional information like tile size, formats and supported CRS are listed in this table. In combination with this feature, you can use the tile scale slider by selecting Settings → Panels (KDE and Windows) or View → Panels (Gnome and MacOSX), then choosing Tile scale. This gives you the available scales from the tile server with a nice slider docked in. Using the Identify Tool Once you have added a WMS server, and if any layer from a WMS server is queryable, you can then use the Identify tool to select a pixel on the map canvas. A query is made to the WMS server for each selection made. The results of the query are returned in plain text. The formatting of this text is dependent on the particular WMS server used. Format selection If multiple output formats are supported by the server, a combo box with supported formats is automatically added to the identify results dialog and the selected format may be stored in the project for the layer. GML format support The Identify tool supports WMS server response (GetFeatureInfo) in GML format (it is called Feature in the QGIS GUI in this context). If “Feature” format is supported by the server and selected, results of the Identify tool 150 Chapter 14. Working with OGC Data QGIS User Guide, Release 2.6 are vector features, as from a regular vector layer. When a single feature is selected in the tree, it is highlighted in the map and it can be copied to the clipboard and pasted to another vector layer. See the example setup of the UMN Mapserver below to support GetFeatureInfo in GML format. # in layer METADATA add which fields should be included and define geometry (example): "gml_include_items" "all" "ows_geometries" "mygeom" "ows_mygeom_type" "polygon" # Then there are two possibilities/formats available, see a) and b): # a) basic (output is generated by Mapserver and does not contain XSD) # in WEB METADATA define formats (example): "wms_getfeatureinfo_formatlist" "application/vnd.ogc.gml,text/html" # b) using OGR (output is generated by OGR, it is send as multipart and contains XSD) # in MAP define OUTPUTFORMAT (example): OUTPUTFORMAT NAME "OGRGML" MIMETYPE "ogr/gml" DRIVER "OGR/GML" FORMATOPTION "FORM=multipart" END # in WEB METADATA define formats (example): "wms_getfeatureinfo_formatlist" "OGRGML,text/html" Viewing Properties Once you have added a WMS server, you can view its properties by right-clicking on it in the legend and selecting Properties. Metadata Tab The tab Metadata displays a wealth of information about the WMS server, generally collected from the capabilities statement returned from that server. Many definitions can be gleaned by reading the WMS standards (see OPEN- GEOSPATIAL-CONSORTIUM in Literature and Web References), but here are a few handy definitions: • Server Properties – WMS Version — The WMS version supported by the server. – Image Formats — The list of MIME-types the server can respond with when drawing the map. QGIS supports whatever formats the underlying Qt libraries were built with, which is typically at least image/png and image/jpeg. – Identity Formats — The list of MIME-types the server can respond with when you use the Identify tool. Currently, QGIS supports the text-plain type. • Layer Properties – Selected — Whether or not this layer was selected when its server was added to this project. – Visible — Whether or not this layer is selected as visible in the legend (not yet used in this version of QGIS). – Can Identify — Whether or not this layer will return any results when the Identify tool is used on it. – Can be Transparent — Whether or not this layer can be rendered with transparency. This version of QGIS will always use transparency if this is Yes and the image encoding supports transparency. – Can Zoom In — Whether or not this layer can be zoomed in by the server. This version of QGIS assumes all WMS layers have this set to Yes. Deficient layers may be rendered strangely. – Cascade Count — WMS servers can act as a proxy to other WMS servers to get the raster data for a layer. This entry shows how many times the request for this layer is forwarded to peer WMS servers for a result. 14.1. QGIS as OGC Data Client 151 QGIS User Guide, Release 2.6 – Fixed Width, Fixed Height — Whether or not this layer has fixed source pixel dimensions. This version of QGIS assumes all WMS layers have this set to nothing. Deficient layers may be rendered strangely. – WGS 84 Bounding Box — The bounding box of the layer, in WGS 84 coordinates. Some WMS servers do not set this correctly (e.g., UTM coordinates are used instead). If this is the case, then the initial view of this layer may be rendered with a very ‘zoomed-out’ appearance by QGIS. The WMS webmaster should be informed of this error, which they may know as the WMS XML elements LatLonBoundingBox, EX_GeographicBoundingBox or the CRS:84 BoundingBox. – Available in CRS — The projections that this layer can be rendered in by the WMS server. These are listed in the WMS-native format. – Available in style — The image styles that this layer can be rendered in by the WMS server. Show WMS legend graphic in table of contents and composer The QGIS WMS data provider is able to display a legend graphic in the table of contents’ layer list and in the map composer. The WMS legend will be shown only if the WMS server has GetLegendGraphic capability and the layer has getCapability url specified, so you additionally have to select a styling for the layer. If a legendGraphic is available, it is shown below the layer. It is little and you have to click on it to open it in real dimension (due to QgsLegendInterface architectural limitation). Clicking on the layer’s legend will open a frame with the legend at full resolution. In the print composer, the legend will be integrated at it’s original (dowloaded) dimension. Resolution of the legend graphic can be set in the item properties under Legend -> WMS LegendGraphic to match your printing requirements The legend will display contextual information based on your current scale. The WMS legend will be shown only if the WMS server has GetLegendGraphic capability and the layer has getCapability url specified, so you have to select a styling. WMS Client Limitations Not all possible WMS client functionality had been included in this version of QGIS. Some of the more noteworthy exceptions follow. Editing WMS Layer Settings Once you’ve completed the Add WMS layer procedure, there is no way to change the settings. A work-around is to delete the layer completely and start again. WMS Servers Requiring Authentication Currently, publicly accessible and secured WMS services are supported. The secured WMS servers can be ac- cessed by public authentication. You can add the (optional) credentials when you add a WMS server. See section Selecting WMS/WMTS Servers for details. Tip: Accessing secured OGC-layers If you need to access secured layers with secured methods other than basic authentication, you can use InteProxy as a transparent proxy, which does support several authentication methods. More information can be found in the InteProxy manual at http://inteproxy.wald.intevation.org. Tip: QGIS WMS Mapserver Since Version 1.7.0, QGIS has its own implementation of a WMS 1.3.0 Mapserver. Read more about this in chapter QGIS as OGC Data Server. 152 Chapter 14. Working with OGC Data QGIS User Guide, Release 2.6 14.1.2 WCS Client A Web Coverage Service (WCS) provides access to raster data in forms that are useful for client-side render- ing, as input into scientific models, and for other clients. The WCS may be compared to the WFS and the WMS. As WMS and WFS service instances, a WCS allows clients to choose portions of a server’s information holdings based on spatial constraints and other query criteria. QGIS has a native WCS provider and supports both version 1.0 and 1.1 (which are significantly different), but currently it prefers 1.0, because 1.1 has many issues (i.e., each server implements it in a different way with various particularities). The native WCS provider handles all network requests and uses all standard QGIS network settings (especially proxy). It is also possible to select cache mode (‘always cache’, ‘prefer cache’, ‘prefer network’, ‘always net- work’), and the provider also supports selection of time position, if temporal domain is offered by the server. 14.1.3 WFS and WFS-T Client In QGIS, a WFS layer behaves pretty much like any other vector layer. You can identify and select features, and view the attribute table. Since QGIS 1.6, editing WFS-T is also supported. In general, adding a WFS layer is very similar to the procedure used with WMS. The difference is that there are no default servers defined, so we have to add our own. Loading a WFS Layer As an example, we use the DM Solutions WFS server and display a layer. The URL is: http://www2.dmsolutions.ca/cgi-bin/mswfs_gmap 1. Click on the Add WFS Layer tool on the Layers toolbar. The Add WFS Layer from a Server dialog appears. 2. Click on [New]. 3. Enter ‘DM Solutions’ as name. 4. Enter the URL (see above). 5. Click [OK]. 6. Choose ‘DM Solutions’ from the Server Connections drop-down list. 7. Click [Connect]. 8. Wait for the list of layers to be populated. 9. Select the Parks layer in the list. 10. Click [Apply] to add the layer to the map. Note that any proxy settings you may have set in your preferences are also recognized. You’ll notice the download progress is visualized in the lower left of the QGIS main window. Once the layer is loaded, you can identify and select a province or two and view the attribute table. Only WFS 1.0.0 is supported. At this time, there have not been many tests against WFS versions implemented in other WFS servers. If you encounter problems with any other WFS server, please do not hesitate to contact the development team. Please refer to section Help and Support for further information about the mailing lists. Tip: Finding WFS Servers You can find additional WFS servers by using Google or your favorite search engine. There are a number of lists with public URLs, some of them maintained and some not. . 14.1. QGIS as OGC Data Client 153 QGIS User Guide, Release 2.6 Figure 14.4: Adding a WFS layer 14.2 QGIS as OGC Data Server QGIS Server is an open source WMS 1.3, WFS 1.0.0 and WCS 1 1.1.1 implementation that, in addition, im- plements advanced cartographic features for thematic mapping. The QGIS Server is a FastCGI/CGI (Common Gateway Interface) application written in C++ that works together with a web server (e.g., Apache, Lighttpd). It is funded by the EU projects Orchestra, Sany and the city of Uster in Switzerland. QGIS Server uses QGIS as back end for the GIS logic and for map rendering. Furthermore, the Qt library is used for graphics and for platform-independent C++ programming. In contrast to other WMS software, the QGIS Server uses cartographic rules as a configuration language, both for the server configuration and for the user- defined cartographic rules. As QGIS desktop and QGIS Server use the same visualization libraries, the maps that are published on the web look the same as in desktop GIS. In one of the following manuals, we will provide a sample configuration to set up a QGIS Server. For now, we recommend to read one of the following URLs to get more information: • http://karlinapp.ethz.ch/qgis_wms/ • http://hub.qgis.org/projects/quantum-gis/wiki/QGIS_Server_Tutorial • http://linfiniti.com/2010/08/qgis-mapserver-a-wms-server-for-the-masses/ 14.2.1 Sample installation on Debian Squeeze At this point, we will give a short and simple sample installation how-to for Debian Squeeze. Many other OSs provide packages for QGIS Server, too. If you have to build it all from source, please refer to the URLs above. Apart from QGIS and QGIS Server, you need a web server, in our case apache2. You can install all packages with aptitude or apt-get install together with other necessary dependency packages. After installation, you should test to confirm that the web server and QGIS Server work as expected. Make sure the apache server is running with /etc/init.d/apache2 start. Open a web browser and type URL: http://localhost. If apache is up, you should see the message ‘It works!’. Now we test the QGIS Server installation. The qgis_mapserv.fcgi is available at /usr/lib/cgi-bin/qgis_mapserv.fcgi and provides a standard WMS that shows the state boundaries of Alaska. Add the WMS with the URL http://localhost/cgi-bin/qgis_mapserv.fcgi as described in Selecting WMS/WMTS Servers. 154 Chapter 14. Working with OGC Data QGIS User Guide, Release 2.6 Figure 14.5: Standard WMS with USA boundaries included in the QGIS Server (KDE) 14.2. QGIS as OGC Data Server 155 QGIS User Guide, Release 2.6 14.2.2 Creating a WMS/WFS/WCS from a QGIS project To provide a new QGIS Server WMS, WFS or WCS, we have to create a QGIS project file with some data. Here, we use the ‘Alaska’ shapefile from the QGIS sample dataset. Define the colors and styles of the layers in QGIS and the project CRS, if not already defined. Figure 14.6: Definitions for a QGIS Server WMS/WFS/WCS project (KDE) Then, go to the OWS Server menu of the Project → Project Properties dialog and provide some information about the OWS in the fields under Service Capabilities. This will appear in the GetCapabilities response of the WMS, WFS or WCS. If you don’t check Service capabilities, QGIS Server will use the information given in the wms_metadata.xml file located in the cgi-bin folder. WMS capabilities In the WMS capabilities section, you can define the extent advertised in the WMS GetCapabilities response by entering the minimum and maximum X and Y values in the fields under Advertised extent. Clicking Use Current Canvas Extent sets these values to the extent currently displayed in the QGIS map canvas. By checking CRS restrictions, you can restrict in which coordinate reference systems (CRS) QGIS Server will offer to render maps. Use the button below to select those CRS from the Coordinate Reference System Selector, or click Used to add the CRS used in the QGIS project to the list. If you have print composers defined in your project, they will be listed in the GetCapabilities response, and they can be used by the GetPrint request to create prints, using one of the print composer layouts as a template. This 156 Chapter 14. Working with OGC Data QGIS User Guide, Release 2.6 is a QGIS-specific extension to the WMS 1.3.0 specification. If you want to exclude any print composer from being published by the WMS, check Exclude composers and click the button below. Then, select a print composer from the Select print composer dialog in order to add it to the excluded composers list. If you want to exclude any layer or layer group from being published by the WMS, check Exclude Layers and click the button below. This opens the Select restricted layers and groups dialog, which allows you to choose the layers and groups that you don’t want to be published. Use the Shift or Ctrl key if you want to select multiple entries at once. You can receive requested GetFeatureInfo as plain text, XML and GML. Default is XML, text or GML format depends the output format choosen for the GetFeatureInfo request. If you wish, you can check Add geometry to feature response. This will include in the GetFeatureInfo response the geometries of the features in a text format. If you want QGIS Server to advertise specific request URLs in the WMS GetCapabilities response, enter the corresponding URL in the Advertised URL field. Furthermore, you can restrict the maximum size of the maps returned by the GetMap request by entering the maximum width and height into the respective fields under Maximums for GetMap request. If one of your layers uses the Map Tip display (i.e. to show text using expressions) this will be listed inside the GetFeatureInfo output. If the layer uses a Value Map for one of his attributes, also this information will be shown in the GetFeatureInfo output. WFS capabilities In the WFS capabilities area, you can select the layers that you want to publish as WFS, and specify if they will allow the update, insert and delete operations. If you enter a URL in the Advertised URL field of the WFS capabilities section, QGIS Server will advertise this specific URL in the WFS GetCapabilities response. WCS capabilities In the WCS capabilities area, you can select the layers that you want to publish as WCS. If you enter a URL in the Advertised URL field of the WCS capabilities section, QGIS Server will advertise this specific URL in the WCS GetCapabilities response. Now, save the session in a project file alaska.qgs. To provide the project as a WMS/WFS, we create a new folder /usr/lib/cgi-bin/project with admin privileges and add the project file alaska.qgs and a copy of the qgis_mapserv.fcgi file - that’s all. Now we test our project WMS, WFS and WCS. Add the WMS, WFS and WCS as described in Loading WMS/WMTS Layers, WFS and WFS-T Client and WCS Client to QGIS and load the data. The URL is: http://localhost/cgi-bin/project/qgis_mapserv.fcgi Fine tuning your OWS For vector layers, the Fields menu of the Layer → Properties dialog allows you to define for each attribute if it will be published or not. By default, all the attributes are published by your WMS and WFS. If you want a specific attribute not to be published, uncheck the corresponding checkbox in the WMS or WFS column. You can overlay watermarks over the maps produced by your WMS by adding text annotations or SVG annotations to the project file. See section Annotation Tools in General Tools for instructions on creating annotations. For annotations to be displayed as watermarks on the WMS output, the Fixed map position check box in the Annotation text dialog must be unchecked. This can be accessed by double clicking the annotation while one of the annotation tools is active. For SVG annotations, you will need either to set the project to save absolute paths (in the General menu of the Project → Project Properties dialog) or to manually modify the path to the SVG image in a way that it represents a valid relative path. Extra parameters supported by the WMS GetMap request In the WMS GetMap request, QGIS Server accepts a couple of extra parameters in addition to the standard parameters according to the OCG WMS 1.3.0 specification: 14.2. QGIS as OGC Data Server 157 QGIS User Guide, Release 2.6 • MAP parameter: Similar to MapServer, the MAP parameter can be used to specify the path to the QGIS project file. You can specify an absolute path or a path relative to the location of the server executable (qgis_mapserv.fcgi). If not specified, QGIS Server searches for .qgs files in the directory where the server executable is located. Example: http://localhost/cgi-bin/qgis_mapserv.fcgi?\ REQUEST=GetMap&MAP=/home/qgis/mymap.qgs&... • DPI parameter: The DPI parameter can be used to specify the requested output resolution. Example: http://localhost/cgi-bin/qgis_mapserv.fcgi?REQUEST=GetMap&DPI=300&... • OPACITIES parameter: Opacity can be set on layer or group level. Allowed values range from 0 (fully transparent) to 255 (fully opaque). Example: http://localhost/cgi-bin/qgis_mapserv.fcgi?\ REQUEST=GetMap&LAYERS=mylayer1,mylayer2&OPACITIES=125,200&... QGIS Server logging To log requests send to server, set the following environment variables: • QGIS_SERVER_LOG_FILE: Specify path and filename. Make sure that server has proper permissions for writing to file. File should be created automatically, just send some requests to server. If it’s not there, check permissions. • QGIS_SERVER_LOG_LEVEL: Specify desired log level. Available values are: – 0 INFO (log all requests), – 1 WARNING, – 2 CRITICAL (log just critical errors, suitable for production purposes). Example: SetEnv QGIS_SERVER_LOG_FILE /var/tmp/qgislog.txt SetEnv QGIS_SERVER_LOG_LEVEL 0 Note • When using Fcgid module use FcgidInitialEnv instead of SetEnv! • Server logging is enabled also if executable is compiled in release mode. Environment variables • QGIS_OPTIONS_PATH: The variable specifies path to directory with settings. It works the same ways as QGIS application –optionspath option. It is looking for settings file in /QGIS/QGIS2.ini. For exaple, to set QGIS server on Apache to use /path/to/config/QGIS/QGIS2.ini settings file, add to Apache config: SetEnv QGIS_OPTIONS_PATH "/path/to/config/" . 158 Chapter 14. Working with OGC Data CHAPTER 15 Working with GPS Data . 15.1 GPS Plugin 15.1.1 What is GPS? GPS, the Global Positioning System, is a satellite-based system that allows anyone with a GPS receiver to find their exact position anywhere in the world. GPS is used as an aid in navigation, for example in airplanes, in boats and by hikers. The GPS receiver uses the signals from the satellites to calculate its latitude, longitude and (sometimes) elevation. Most receivers also have the capability to store locations (known as waypoints), sequences of locations that make up a planned route and a tracklog or track of the receiver’s movement over time. Waypoints, routes and tracks are the three basic feature types in GPS data. QGIS displays waypoints in point layers, while routes and tracks are displayed in linestring layers. 15.1.2 Loading GPS data from a file There are dozens of different file formats for storing GPS data. The format that QGIS uses is called GPX (GPS eXchange format), which is a standard interchange format that can contain any number of waypoints, routes and tracks in the same file. To load a GPX file, you first need to load the plugin. Plugins → Plugin Manager... opens the Plugin Manager Dialog. Activate the GPS Tools checkbox. When this plugin is loaded, two buttons with a small handheld GPS device will show up in the toolbar: • Create new GPX Layer • GPS Tools For working with GPS data, we provide an example GPX file available in the QGIS sample dataset: qgis_sample_data/gps/national_monuments.gpx. See section Sample Data for more information about the sample data. 1. Select Vector → GPS → GPS Tools or click the GPS Tools icon in the toolbar and open the Load GPX file tab (see figure_GPS_1). 2. Browse to the folder qgis_sample_data/gps/, select the GPX file national_monuments.gpx and click [Open]. Use the [Browse...] button to select the GPX file, then use the checkboxes to select the feature types you want to load from that GPX file. Each feature type will be loaded in a separate layer when you click [OK]. The file national_monuments.gpx only includes waypoints. 159 QGIS User Guide, Release 2.6 Figure 15.1: The GPS Tools dialog window Note: GPS units allow you to store data in different coordinate systems. When downloading a GPX file (from your GPS unit or a web site) and then loading it in QGIS, be sure that the data stored in the GPX file uses WGS 84 (latitude/longitude). QGIS expects this, and it is the official GPX specification. See http://www.topografix.com/GPX/1/1/. 15.1.3 GPSBabel Since QGIS uses GPX files, you need a way to convert other GPS file formats to GPX. This can be done for many formats using the free program GPSBabel, which is available at http://www.gpsbabel.org. This program can also transfer GPS data between your computer and a GPS device. QGIS uses GPSBabel to do these things, so it is recommended that you install it. However, if you just want to load GPS data from GPX files you will not need it. Version 1.2.3 of GPSBabel is known to work with QGIS, but you should be able to use later versions without any problems. 15.1.4 Importing GPS data To import GPS data from a file that is not a GPX file, you use the tool Import other file in the GPS Tools dialog. Here, you select the file that you want to import (and the file type), which feature type you want to import from it, where you want to store the converted GPX file and what the name of the new layer should be. Note that not all GPS data formats will support all three feature types, so for many formats you will only be able to choose between one or two types. 15.1.5 Downloading GPS data from a device QGIS can use GPSBabel to download data from a GPS device directly as new vector layers. For this we use the Download from GPS tab of the GPS Tools dialog (see Figure_GPS_2). Here, we select the type of GPS device, the port that it is connected to (or USB if your GPS supports this), the feature type that you want to download, the GPX file where the data should be stored, and the name of the new layer. The device type you select in the GPS device menu determines how GPSBabel tries to communicate with your GPS device. If none of the available types work with your GPS device, you can create a new type (see section Defining new device types). The port may be a file name or some other name that your operating system uses as a reference to the physical port in your computer that the GPS device is connected to. It may also be simply USB, for USB-enabled GPS units. • On Linux, this is something like /dev/ttyS0 or /dev/ttyS1. • On Windows, it is COM1 or COM2. 160 Chapter 15. Working with GPS Data QGIS User Guide, Release 2.6 Figure 15.2: The download tool When you click [OK], the data will be downloaded from the device and appear as a layer in QGIS. 15.1.6 Uploading GPS data to a device You can also upload data directly from a vector layer in QGIS to a GPS device using the Upload to GPS tab of the GPS Tools dialog. To do this, you simply select the layer that you want to upload (which must be a GPX layer), your GPS device type, and the port (or USB) that it is connected to. Just as with the download tool, you can specify new device types if your device isn’t in the list. This tool is very useful in combination with the vector-editing capabilities of QGIS. It allows you to load a map, create waypoints and routes, and then upload them and use them on your GPS device. 15.1.7 Defining new device types There are lots of different types of GPS devices. The QGIS developers can’t test all of them, so if you have one that does not work with any of the device types listed in the Download from GPS and Upload to GPS tools, you can define your own device type for it. You do this by using the GPS device editor, which you start by clicking the [Edit devices] button in the download or the upload tab. To define a new device, you simply click the [New device] button, enter a name, enter download and upload commands for your device, and click the [Update device] button. The name will be listed in the device menus in the upload and download windows – it can be any string. The download command is the command that is used to download data from the device to a GPX file. This will probably be a GPSBabel command, but you can use any other command line program that can create a GPX file. QGIS will replace the keywords %type,%in, and %out when it runs the command. %type will be replaced by -w if you are downloading waypoints, -r if you are downloading routes and -t if you are downloading tracks. These are command-line options that tell GPSBabel which feature type to download. %in will be replaced by the port name that you choose in the download window and %out will be replaced by the name you choose for the GPX file that the downloaded data should be stored in. So, if you create a device type with the download command gpsbabel %type -i garmin -o gpx %in %out (this is actually the download command for the predefined device type ‘Garmin serial’) and then use it to download waypoints from port /dev/ttyS0 to the file output.gpx, QGIS will replace the keywords and run the command gpsbabel -w -i garmin -o gpx /dev/ttyS0 output.gpx. The upload command is the command that is used to upload data to the device. The same keywords are used, but %in is now replaced by the name of the GPX file for the layer that is being uploaded, and %out is replaced by the port name. You can learn more about GPSBabel and its available command line options at http://www.gpsbabel.org. Once you have created a new device type, it will appear in the device lists for the download and upload tools. 15.1. GPS Plugin 161 QGIS User Guide, Release 2.6 15.1.8 Download of points/tracks from GPS units As described in previous sections QGIS uses GPSBabel to download points/tracks directly in the project. QGIS comes out of the box with a pre-defined profile to download from Garmin devices. Unfortunately there is a bug #6318 that does not allow create other profiles, so downloading directly in QGIS using the GPS Tools is at the moment limited to Garmin USB units. Garmin GPSMAP 60cs MS Windows Install the Garmin USB drivers from http://www8.garmin.com/support/download_details.jsp?id=591 Connect the unit. Open GPS Tools and use type=garmin serial and port=usb: Fill the fields Layer name and Output file. Sometimes it seems to have problems saving in a certain folder, using something like c:\temp usually works. Ubuntu/Mint GNU/Linux It is first needed an issue about the permissions of the device, as described at https://wiki.openstreetmap.org/wiki/USB_Garmin_on_GNU/Linux. You can try to create a file /etc/udev/rules.d/51-garmin.rules containing this rule ATTRS{idVendor}=="091e", ATTRS{idProduct}=="0003", MODE="666" After that is necessary to be sure that the garmin_gps kernel module is not loaded rmmod garmin_gps and then you can use the GPS Tools. Unfortunately there seems to be a bug #7182 and usually QGIS freezes several times before the operation work fine. BTGP-38KM datalogger (only Bluetooth) MS Windows The already referred bug does not allow to download the data from within QGIS, so it is needed to use GPSBabel from the command line or using its interface. The working command is gpsbabel -t -i skytraq,baud=9600,initbaud=9600 -f COM9 -o gpx -F C:/GPX/aaa.gpx Ubuntu/Mint GNU/Linux Use same command (or settings if you use GPSBabel GUI) as in Windows. On Linux it maybe somehow common to get a message like skytraq: Too many read errors on serial port it is just a matter to turn off and on the datalogger and try again. BlueMax GPS-4044 datalogger (both BT and USB) MS Windows Note: It needs to install its drivers before using it on Windows 7. See in the manufacturer site for the proper download. Downloading with GPSBabel, both with USB and BT returns always an error like gpsbabel -t -i mtk -f COM12 -o gpx -F C:/temp/test.gpx mtk_logger: Can’t create temporary file data.bin Error running gpsbabel: Process exited unsucessfully with code 1 162 Chapter 15. Working with GPS Data QGIS User Guide, Release 2.6 Ubuntu/Mint GNU/Linux With USB After having connected the cable use the dmesg command to understand what port is being used, for example /dev/ttyACM3. Then as usual use GPSBabel from the CLI or GUI gpsbabel -t -i mtk -f /dev/ttyACM3 -o gpx -F /home/user/bluemax.gpx With Bluetooth Use Blueman Device Manager to pair the device and make it available through a system port, then run GPSBabel gpsbabel -t -i mtk -f /dev/rfcomm0 -o gpx -F /home/user/bluemax_bt.gpx . 15.2 Live GPS tracking To activate live GPS tracking in QGIS, you need to select Settings → Panels GPS information. You will get a new docked window on the left side of the canvas. There are four possible screens in this GPS tracking window: • GPS position coordinates and an interface for manually entering vertices and features • GPS signal strength of satellite connections • GPS polar screen showing number and polar position of satellites • GPS options screen (see figure_gps_options) With a plugged-in GPS receiver (has to be supported by your operating system), a simple click on [Connect] con- nects the GPS to QGIS. A second click (now on [Disconnect]) disconnects the GPS receiver from your computer. For GNU/Linux, gpsd support is integrated to support connection to most GPS receivers. Therefore, you first have to configure gpsd properly to connect QGIS to it. Warning: If you want to record your position to the canvas, you have to create a new vector layer first and switch it to editable status to be able to record your track. 15.2.1 Position and additional attributes If the GPS is receiving signals from satellites, you will see your position in latitude, longitude and altitude together with additional attributes. 15.2.2 GPS signal strength Here, you can see the signal strength of the satellites you are receiving signals from. 15.2.3 GPS polar window If you want to know where in the sky all the connected satellites are, you have to switch to the polar screen. You can also see the ID numbers of the satellites you are receiving signals from. 15.2. Live GPS tracking 163 QGIS User Guide, Release 2.6 Figure 15.3: GPS tracking position and additional attributes Figure 15.4: GPS tracking signal strength 164 Chapter 15. Working with GPS Data QGIS User Guide, Release 2.6 Figure 15.5: GPS tracking polar window 15.2.4 GPS options In case of connection problems, you can switch between: • Autodetect • Internal • Serial device • gpsd (selecting the Host, Port and Device your GPS is connected to) A click on [Connect] again initiates the connection to the GPS receiver. You can activate Automatically save added features when you are in editing mode. Or you can activate Automatically add points to the map canvas with a certain width and color. Activating Cursor, you can use a slider to shrink and grow the position cursor on the canvas. Activating Map centering allows you to decide in which way the canvas will be updated. This includes ‘always’, ‘when leaving’, if your recorded coordinates start to move out of the canvas, or ‘never’, to keep map extent. Finally, you can activate Log file and define a path and a file where log messages about the GPS tracking are logged. If you want to set a feature manually, you have to go back to Position and click on [Add Point] or [Add track point]. 15.2.5 Connect to a Bluetooth GPS for live tracking With QGIS you can connect a Bluetooth GPS for field data collection. To perform this task you need a GPS Bluetooth device and a Bluetooth receiver on your computer. At first you must let your GPS device be recognized and paired to the computer. Turn on the GPS, go to the Bluetooth icon on your notification area and search for a New Device. On the right side of the Device selection mask make sure that all devices are selected so your GPS unit will probably appear among those available. In the next step a serial connection service should be available, select it and click on [Configure] button. Remember the number of the COM port assigned to the GPS connection as resulting by the Bluetooth properties. After the GPS has been recognized, make the pairing for the connection. Usually the autorization code is 0000. 15.2. Live GPS tracking 165 QGIS User Guide, Release 2.6 Figure 15.6: GPS tracking options window 166 Chapter 15. Working with GPS Data QGIS User Guide, Release 2.6 Now open GPS information panel and switch to GPS options screen. Select the COM port assigned to the GPS connection and click the [Connect]. After a while a cursor indicating your position should appear. If QGIS can’t receive GPS data, then you should restart your GPS device, wait 5-10 seconds then try to connect again. Usually this solution work. If you receive again a connection error make sure you don’t have another Bluetooth receiver near you, paired with the same GPS unit. 15.2.6 Using GPSMAP 60cs MS Windows Easiest way to make it work is to use a middleware (freeware, not open) called GPSGate. Launch the program, make it scan for GPS devices (works for both USB and BT ones) and then in QGIS just click [Connect] in the Live tracking panel using the Autodetect mode. Ubuntu/Mint GNU/Linux As for Windows the easiest way is to use a server in the middle, in this case GPSD, so sudo apt-get install gpsd Then load the garmin_gps kernel module sudo modprobe garmin_gps And then connect the unit. Then check with dmesg the actual device being used bu the unit, for example /dev/ttyUSB0. Now you can launch gpsd gpsd/dev/ttyUSB0 And finally connect with the QGIS live tracking tool. 15.2.7 Using BTGP-38KM datalogger (only Bluetooth) Using GPSD (under Linux) or GPSGate (under Windows) is effortless. 15.2.8 Using BlueMax GPS-4044 datalogger (both BT and USB) MS Windows The live tracking works for both USB and BT modes, by using GPSGate or even without it, just use the Autodetect mode, or point the tool the right port. Ubuntu/Mint GNU/Linux For USB The live tracking works both with GPSD gpsd/dev/ttyACM3 or without it, by connecting the QGIS live tracking tool directly to the device (for example /dev/ttyACM3). For Bluetooth The live tracking works both with GPSD 15.2. Live GPS tracking 167 QGIS User Guide, Release 2.6 gpsd/dev/rfcomm0 or without it, by connecting the QGIS live tracking tool directly to the device (for example /dev/rfcomm0). . 168 Chapter 15. Working with GPS Data CHAPTER 16 GRASS GIS Integration The GRASS plugin provides access to GRASS GIS databases and functionalities (see GRASS-PROJECT in Lit- erature and Web References). This includes visualizing GRASS raster and vector layers, digitizing vector layers, editing vector attributes, creating new vector layers and analysing GRASS 2-D and 3-D data with more than 400 GRASS modules. In this section, we’ll introduce the plugin functionalities and give some examples of managing and working with GRASS data. The following main features are provided with the toolbar menu when you start the GRASS plugin, as described in section sec_starting_grass: • Open mapset • New mapset • Close mapset • Add GRASS vector layer • Add GRASS raster layer • Create new GRASS vector • Edit GRASS vector layer • Open GRASS tools • Display current GRASS region • Edit current GRASS region 16.1 Starting the GRASS plugin To use GRASS functionalities and/or visualize GRASS vector and raster layers in QGIS, you must select and load the GRASS plugin with the Plugin Manager. Therefore, go to the menu Plugins → Manage Plugins, select GRASS and click [OK]. You can now start loading raster and vector layers from an existing GRASS LOCATION (see section sec_load_grassdata). Or, you can create a new GRASS LOCATION with QGIS (see section Creating a new GRASS LOCATION) and import some raster and vector data (see section Importing data into a GRASS LOCA- TION) for further analysis with the GRASS Toolbox (see section The GRASS Toolbox). 169 QGIS User Guide, Release 2.6 16.2 Loading GRASS raster and vector layers With the GRASS plugin, you can load vector or raster layers using the appropriate button on the toolbar menu. As an example, we will use the QGIS Alaska dataset (see section Sample Data). It includes a small sample GRASS LOCATION with three vector layers and one raster elevation map. 1. Create a new folder called grassdata, download the QGIS ‘Alaska’ dataset qgis_sample_data.zip from http://download.osgeo.org/qgis/data/ and unzip the file into grassdata. 2. Start QGIS. 3. If not already done in a previous QGIS session, load the GRASS plugin clicking on Plugins → Manage Plugins and activate GRASS. The GRASS toolbar appears in the QGIS main window. 4. In the GRASS toolbar, click the Open mapset icon to bring up the MAPSET wizard. 5. For Gisdbase, browse and select or enter the path to the newly created folder grassdata. 6. You should now be able to select the LOCATION alaska and the MAPSET demo. 7. Click [OK]. Notice that some previously disabled tools in the GRASS toolbar are now enabled. 8. Click on Add GRASS raster layer, choose the map name gtopo30 and click [OK]. The elevation layer will be visualized. 9. Click on Add GRASS vector layer, choose the map name alaska and click [OK]. The Alaska boundary vector layer will be overlayed on top of the gtopo30 map. You can now adapt the layer properties as described in chapter The Vector Properties Dialog (e.g., change opacity, fill and outline color). 10. Also load the other two vector layers, rivers and airports, and adapt their properties. As you see, it is very simple to load GRASS raster and vector layers in QGIS. See the following sections for editing GRASS data and creating a new LOCATION. More sample GRASS LOCATIONs are available at the GRASS website at http://grass.osgeo.org/download/sample-data/. Tip: GRASS Data Loading If you have problems loading data or QGIS terminates abnormally, check to make sure you have loaded the GRASS plugin properly as described in section Starting the GRASS plugin. 16.3 GRASS LOCATION and MAPSET GRASS data are stored in a directory referred to as GISDBASE. This directory, often called grassdata, must be created before you start working with the GRASS plugin in QGIS. Within this directory, the GRASS GIS data are organized by projects stored in subdirectories called LOCATIONs. Each LOCATION is defined by its coordinate system, map projection and geographical boundaries. Each LOCATION can have several MAPSETs (subdirectories of the LOCATION) that are used to subdivide the project into different topics or subregions, or as workspaces for individual team members (see Neteler & Mitasova 2008 in Literature and Web References). In order to analyze vector and raster layers with GRASS modules, you must import them into a GRASS LOCATION. (This is not strictly true – with the GRASS modules r.external and v.external you can create read-only links to external GDAL/OGR-supported datasets without importing them. But because this is not the usual way for beginners to work with GRASS, this functionality will not be described here.) 16.3.1 Creating a new GRASS LOCATION As an example, here is how the sample GRASS LOCATION alaska, which is projected in Albers Equal Area projection with unit feet was created for the QGIS sample dataset. This sample GRASS LOCATION alaska 170 Chapter 16. GRASS GIS Integration QGIS User Guide, Release 2.6 Figure 16.1: GRASS data in the alaska LOCATION will be used for all examples and exercises in the following GRASS-related sections. It is useful to download and install the dataset on your computer (see Sample Data). 1. Start QGIS and make sure the GRASS plugin is loaded. 2. Visualize the alaska.shp shapefile (see section Loading a Shapefile) from the QGIS Alaska dataset (see Sample Data). 3. In the GRASS toolbar, click on the New mapset icon to bring up the MAPSET wizard. 4. Select an existing GRASS database (GISDBASE) folder grassdata, or create one for the new LOCATION using a file manager on your computer. Then click [Next]. 5. We can use this wizard to create a new MAPSET within an existing LOCATION (see section Adding a new MAPSET) or to create a new LOCATION altogether. Select Create new location (see fig- ure_grass_location_2). 6. Enter a name for the LOCATION – we used ‘alaska’ – and click [Next]. 7. Define the projection by clicking on the radio button Projection to enable the projection list. 8. We are using Albers Equal Area Alaska (feet) projection. Since we happen to know that it is represented by the EPSG ID 2964, we enter it in the search box. (Note: If you want to repeat this process for another LOCATION and projection and haven’t memorized the EPSG ID, click on the CRS Status icon in the lower right-hand corner of the status bar (see section Working with Projections)). 9. In Filter, insert 2964 to select the projection. 10. Click [Next]. 11. To define the default region, we have to enter the LOCATION bounds in the north, south, east, and west directions. Here, we simply click on the button [Set current |qg| extent], to apply the extent of the loaded layer alaska.shp as the GRASS default region extent. 12. Click [Next]. 13. We also need to define a MAPSET within our new LOCATION (this is necessary when creating a new LOCATION). You can name it whatever you like - we used ‘demo’. GRASS automatically creates a special MAPSET called PERMANENT, designed to store the core data for the project, its default spatial extent and coordinate system definitions (see Neteler & Mitasova 2008 in Literature and Web References). 14. Check out the summary to make sure it’s correct and click [Finish]. 15. The new LOCATION, ‘alaska’, and two MAPSETs, ‘demo’ and ‘PERMANENT’, are created. The currently opened working set is ‘demo’, as you defined. 16.3. GRASS LOCATION and MAPSET 171 QGIS User Guide, Release 2.6 16. Notice that some of the tools in the GRASS toolbar that were disabled are now enabled. Figure 16.2: Creating a new GRASS LOCATION or a new MAPSET in QGIS If that seemed like a lot of steps, it’s really not all that bad and a very quick way to create a LOCATION. The LOCATION ‘alaska’ is now ready for data import (see section Importing data into a GRASS LOCATION). You can also use the already-existing vector and raster data in the sample GRASS LOCATION ‘alaska’, included in the QGIS ‘Alaska’ dataset Sample Data, and move on to section The GRASS vector data model. 16.3.2 Adding a new MAPSET A user has write access only to a GRASS MAPSET he or she created. This means that besides access to your own MAPSET, you can read maps in other users’ MAPSETs (and they can read yours), but you can modify or remove only the maps in your own MAPSET. All MAPSETs include a WIND file that stores the current boundary coordinate values and the currently selected raster resolution (see Neteler & Mitasova 2008 in Literature and Web References, and section The GRASS region tool). 1. Start QGIS and make sure the GRASS plugin is loaded. 2. In the GRASS toolbar, click on the New mapset icon to bring up the MAPSET wizard. 3. Select the GRASS database (GISDBASE) folder grassdata with the LOCATION ‘alaska’, where we want to add a further MAPSET called ‘test’. 4. Click [Next]. 5. We can use this wizard to create a new MAPSET within an existing LOCATION or to create a new LOCATION altogether. Click on the radio button Select location (see figure_grass_location_2) and click [Next]. 6. Enter the name text for the new MAPSET. Below in the wizard, you see a list of existing MAPSETs and corresponding owners. 7. Click [Next], check out the summary to make sure it’s all correct and click [Finish]. 16.4 Importing data into a GRASS LOCATION This section gives an example of how to import raster and vector data into the ‘alaska’ GRASS LOCATION provided by the QGIS ‘Alaska’ dataset. Therefore, we use the landcover raster map landcover.img and the vector GML file lakes.gml from the QGIS ‘Alaska’ dataset (see Sample Data). 172 Chapter 16. GRASS GIS Integration QGIS User Guide, Release 2.6 1. Start QGIS and make sure the GRASS plugin is loaded. 2. In the GRASS toolbar, click the Open MAPSET icon to bring up the MAPSET wizard. 3. Select as GRASS database the folder grassdata in the QGIS Alaska dataset, as LOCATION ‘alaska’, as MAPSET ‘demo’ and click [OK]. 4. Now click the Open GRASS tools icon. The GRASS Toolbox (see section The GRASS Toolbox) dialog appears. 5. To import the raster map landcover.img, click the module r.in.gdal in the Modules Tree tab. This GRASS module allows you to import GDAL-supported raster files into a GRASS LOCATION. The module dialog for r.in.gdal appears. 6. Browse to the folder raster in the QGIS ‘Alaska’ dataset and select the file landcover.img. 7. As raster output name, define landcover_grass and click [Run]. In the Output tab, you see the currently running GRASS command r.in.gdal -o input=/path/to/landcover.img output=landcover_grass. 8. When it says Succesfully finished, click [View output]. The landcover_grass raster layer is now imported into GRASS and will be visualized in the QGIS canvas. 9. To import the vector GML file lakes.gml, click the module v.in.ogr in the Modules Tree tab. This GRASS module allows you to import OGR-supported vector files into a GRASS LOCATION. The module dialog for v.in.ogr appears. 10. Browse to the folder gml in the QGIS ‘Alaska’ dataset and select the file lakes.gml as OGR file. 11. As vector output name, define lakes_grass and click [Run]. You don’t have to care about the other options in this example. In the Output tab you see the currently running GRASS command v.in.ogr -o dsn=/path/to/lakes.gml output=lakes\_grass. 12. When it says Succesfully finished, click [View output]. The lakes_grass vector layer is now imported into GRASS and will be visualized in the QGIS canvas. 16.5 The GRASS vector data model It is important to understand the GRASS vector data model prior to digitizing. In general, GRASS uses a topological vector model. This means that areas are not represented as closed polygons, but by one or more boundaries. A boundary between two adjacent areas is digitized only once, and it is shared by both areas. Boundaries must be connected and closed without gaps. An area is identified (and labeled) by the centroid of the area. Besides boundaries and centroids, a vector map can also contain points and lines. All these geometry elements can be mixed in one vector and will be represented in different so-called ‘layers’ inside one GRASS vector map. So in GRASS, a layer is not a vector or raster map but a level inside a vector layer. This is important to distinguish carefully. (Although it is possible to mix geometry elements, it is unusual and, even in GRASS, only used in special cases such as vector network analysis. Normally, you should prefer to store different geometry elements in different layers.) It is possible to store several ‘layers’ in one vector dataset. For example, fields, forests and lakes can be stored in one vector. An adjacent forest and lake can share the same boundary, but they have separate attribute tables. It is also possible to attach attributes to boundaries. An example might be the case where the boundary between a lake and a forest is a road, so it can have a different attribute table. The ‘layer’ of the feature is defined by the ‘layer’ inside GRASS. ‘Layer’ is the number which defines if there is more than one layer inside the dataset (e.g., if the geometry is forest or lake). For now, it can be only a number. In the future, GRASS will also support names as fields in the user interface. Attributes can be stored inside the GRASS LOCATION as dBase or SQLite3 or in external database tables, for example, PostgreSQL, MySQL, Oracle, etc. 16.5. The GRASS vector data model 173 QGIS User Guide, Release 2.6 Attributes in database tables are linked to geometry elements using a ‘category’ value. ‘Category’ (key, ID) is an integer attached to geometry primitives, and it is used as the link to one key column in the database table. Tip: Learning the GRASS Vector Model The best way to learn the GRASS vector model and its capabilities is to download one of the many GRASS tutorials where the vector model is described more deeply. See http://grass.osgeo.org/documentation/manuals/ for more information, books and tutorials in several languages. 16.6 Creating a new GRASS vector layer To create a new GRASS vector layer with the GRASS plugin, click the Create new GRASS vector toolbar icon. Enter a name in the text box, and you can start digitizing point, line or polygon geometries following the procedure described in section Digitizing and editing a GRASS vector layer. In GRASS, it is possible to organize all sorts of geometry types (point, line and area) in one layer, because GRASS uses a topological vector model, so you don’t need to select the geometry type when creating a new GRASS vector. This is different from shapefile creation with QGIS, because shapefiles use the Simple Feature vector model (see section Creating new Vector layers). Tip: Creating an attribute table for a new GRASS vector layer If you want to assign attributes to your digitized geometry features, make sure to create an attribute table with columns before you start digitizing (see figure_grass_digitizing_5). 16.7 Digitizing and editing a GRASS vector layer The digitizing tools for GRASS vector layers are accessed using the Edit GRASS vector layer icon on the toolbar. Make sure you have loaded a GRASS vector and it is the selected layer in the legend before clicking on the edit tool. Figure figure_grass_digitizing_2 shows the GRASS edit dialog that is displayed when you click on the edit tool. The tools and settings are discussed in the following sections. Tip: Digitizing polygons in GRASS If you want to create a polygon in GRASS, you first digitize the boundary of the polygon, setting the mode to ‘No category’. Then you add a centroid (label point) into the closed boundary, setting the mode to ‘Next not used’. The reason for this is that a topological vector model links the attribute information of a polygon always to the centroid and not to the boundary. Toolbar In figure_grass_digitizing_1, you see the GRASS digitizing toolbar icons provided by the GRASS plugin. Table table_grass_digitizing_1 explains the available functionalities. Figure 16.3: GRASS Digitizing Toolbar 174 Chapter 16. GRASS GIS Integration QGIS User Guide, Release 2.6 Icon Tool Purpose New Point Digitize new point New Line Digitize new line New Boundary Digitize new boundary (finish by selecting new tool) New Centroid Digitize new centroid (label existing area) Move vertex Move one vertex of existing line or boundary and identify new position Add vertex Add a new vertex to existing line Delete vertex Delete vertex from existing line (confirm selected vertex by another click) Move element Move selected boundary, line, point or centroid and click on new position Split line Split an existing line into two parts Delete element Delete existing boundary, line, point or centroid (confirm selected element by another click) Edit attributes Edit attributes of selected element (note that one element can represent more features, see above) Close Close session and save current status (rebuilds topology afterwards) Table GRASS Digitizing 1: GRASS Digitizing Tools Category Tab The Category tab allows you to define the way in which the category values will be assigned to a new geometry element. Figure 16.4: GRASS Digitizing Category Tab • Mode: The category value that will be applied to new geometry elements. – Next not used - Apply next not yet used category value to geometry element. – Manual entry - Manually define the category value for the geometry element in the ‘Category’ entry field. – No category - Do not apply a category value to the geometry element. This is used, for instance, for area boundaries, because the category values are connected via the centroid. • Category - The number (ID) that is attached to each digitized geometry element. It is used to connect each geometry element with its attributes. 16.7. Digitizing and editing a GRASS vector layer 175 QGIS User Guide, Release 2.6 • Field (layer) - Each geometry element can be connected with several attribute tables using different GRASS geometry layers. The default layer number is 1. Tip: Creating an additional GRASS ‘layer’ with |qg| If you would like to add more layers to your dataset, just add a new number in the ‘Field (layer)’ entry box and press return. In the Table tab, you can create your new table connected to your new layer. Settings Tab The Settings tab allows you to set the snapping in screen pixels. The threshold defines at what distance new points or line ends are snapped to existing nodes. This helps to prevent gaps or dangles between boundaries. The default is set to 10 pixels. Figure 16.5: GRASS Digitizing Settings Tab Symbology Tab The Symbology tab allows you to view and set symbology and color settings for various geometry types and their topological status (e.g., closed / opened boundary). Figure 16.6: GRASS Digitizing Symbology Tab Table Tab The Table tab provides information about the database table for a given ‘layer’. Here, you can add new columns to an existing attribute table, or create a new database table for a new GRASS vector layer (see section Creating a new GRASS vector layer). Tip: GRASS Edit Permissions 176 Chapter 16. GRASS GIS Integration QGIS User Guide, Release 2.6 Figure 16.7: GRASS Digitizing Table Tab You must be the owner of the GRASS MAPSET you want to edit. It is impossible to edit data layers in a MAPSET that is not yours, even if you have write permission. 16.8 The GRASS region tool The region definition (setting a spatial working window) in GRASS is important for working with raster layers. Vector analysis is by default not limited to any defined region definitions. But all newly created rasters will have the spatial extension and resolution of the currently defined GRASS region, regardless of their original extension and resolution. The current GRASS region is stored in the $LOCATION/$MAPSET/WIND file, and it defines north, south, east and west bounds, number of columns and rows, horizontal and vertical spatial resolution. It is possible to switch on and off the visualization of the GRASS region in the QGIS canvas using the Display current GRASS region button. With the Edit current GRASS region icon, you can open a dialog to change the current region and the symbology of the GRASS region rectangle in the QGIS canvas. Type in the new region bounds and resolution, and click [OK]. The dialog also allows you to select a new region interactively with your mouse on the QGIS canvas. Therefore, click with the left mouse button in the QGIS canvas, open a rectangle, close it using the left mouse button again and click [OK]. The GRASS module g.region provides a lot more parameters to define an appropriate region extent and reso- lution for your raster analysis. You can use these parameters with the GRASS Toolbox, described in section The GRASS Toolbox. 16.9 The GRASS Toolbox The Open GRASS Tools box provides GRASS module functionalities to work with data inside a selected GRASS LOCATION and MAPSET. To use the GRASS Toolbox you need to open a LOCATION and MAPSET that you have write permission for (usually granted, if you created the MAPSET). This is necessary, because new raster or vector layers created during analysis need to be written to the currently selected LOCATION and MAPSET. 16.9.1 Working with GRASS modules The GRASS shell inside the GRASS Toolbox provides access to almost all (more than 300) GRASS modules in a command line interface. To offer a more user-friendly working environment, about 200 of the available GRASS modules and functionalities are also provided by graphical dialogs within the GRASS plugin Toolbox. 16.8. The GRASS region tool 177 QGIS User Guide, Release 2.6 Figure 16.8: GRASS Toolbox and Module Tree A complete list of GRASS modules available in the graphical Toolbox in QGIS version 2.6 is available in the GRASS wiki at http://grass.osgeo.org/wiki/GRASS-QGIS_relevant_module_list. It is also possible to customize the GRASS Toolbox content. This procedure is described in section Customizing the GRASS Toolbox. As shown in figure_grass_toolbox_1, you can look for the appropriate GRASS module using the thematically grouped Modules Tree or the searchable Modules List tab. By clicking on a graphical module icon, a new tab will be added to the Toolbox dialog, providing three new sub-tabs: Options, Output and Manual. Options The Options tab provides a simplified module dialog where you can usually select a raster or vector layer visualized in the QGIS canvas and enter further module-specific parameters to run the module. The provided module parameters are often not complete to keep the dialog clear. If you want to use further module parameters and flags, you need to start the GRASS shell and run the module in the command line. A new feature since QGIS 1.8 is the support for a Show Advanced Options button below the simplified module dialog in the Options tab. At the moment, it is only added to the module v.in.ascii as an example of use, but it will probably be part of more or all modules in the GRASS Toolbox in future versions of QGIS. This allows you to use the complete GRASS module options without the need to switch to the GRASS shell. Output The Output tab provides information about the output status of the module. When you click the [Run] button, the module switches to the Output tab and you see information about the analysis process. If all works well, you will finally see a Successfully finished message. Manual The Manual tab shows the HTML help page of the GRASS module. You can use it to check further module parameters and flags or to get a deeper knowledge about the purpose of the module. At the end of each module manual page, you see further links to the Main Help index, the Thematic index and the Full index. These links provide the same information as the module g.manual. Tip: Display results immediately If you want to display your calculation results immediately in your map canvas, you can use the ‘View Output’ button at the bottom of the module tab. 178 Chapter 16. GRASS GIS Integration QGIS User Guide, Release 2.6 Figure 16.9: GRASS Toolbox Module Options Figure 16.10: GRASS Toolbox Module Output 16.9. The GRASS Toolbox 179 QGIS User Guide, Release 2.6 Figure 16.11: GRASS Toolbox Module Manual 16.9.2 GRASS module examples The following examples will demonstrate the power of some of the GRASS modules. Creating contour lines The first example creates a vector contour map from an elevation raster (DEM). Here, it is assumed that you have the Alaska LOCATION set up as explained in section Importing data into a GRASS LOCATION. • First, open the location by clicking the Open mapset button and choosing the Alaska location. • Now load the gtopo30 elevation raster by clicking Add GRASS raster layer and selecting the gtopo30 raster from the demo location. • Now open the Toolbox with the Open GRASS tools button. • In the list of tool categories, double-click Raster → Surface Management → Generate vector contour lines. • Now a single click on the tool r.contour will open the tool dialog as explained above (see Working with GRASS modules). The gtopo30 raster should appear as the Name of input raster. • Type into the Increment between Contour levels the value 100. (This will create contour lines at intervals of 100 meters.) • Type into the Name for output vector map the name ctour_100. • Click [Run] to start the process. Wait for several moments until the message Successfully finished appears in the output window. Then click [View Output] and [Close]. Since this is a large region, it will take a while to display. After it finishes rendering, you can open the layer properties window to change the line color so that the contours appear clearly over the elevation raster, as in The Vector Properties Dialog. Next, zoom in to a small, mountainous area in the center of Alaska. Zooming in close, you will notice that the contours have sharp corners. GRASS offers the v.generalize tool to slightly alter vector maps while keeping 180 Chapter 16. GRASS GIS Integration QGIS User Guide, Release 2.6 their overall shape. The tool uses several different algorithms with different purposes. Some of the algorithms (i.e., Douglas Peuker and Vertex Reduction) simplify the line by removing some of the vertices. The resulting vector will load faster. This process is useful when you have a highly detailed vector, but you are creating a very small-scale map, so the detail is unnecessary. Tip: The simplify tool Note that the QGIS fTools plugin has a Simplify geometries → tool that works just like the GRASS v.generalize Douglas-Peuker algorithm. However, the purpose of this example is different. The contour lines created by r.contour have sharp angles that should be smoothed. Among the v.generalize algorithms, there is Chaiken’s, which does just that (also Hermite splines). Be aware that these algorithms can add additional vertices to the vector, causing it to load even more slowly. • Open the GRASS Toolbox and double-click the categories Vector → Develop map → Generalization, then click on the v.generalize module to open its options window. • Check that the ‘ctour_100’ vector appears as the Name of input vector. • From the list of algorithms, choose Chaiken’s. Leave all other options at their default, and scroll down to the last row to enter in the field Name for output vector map ‘ctour_100_smooth’, and click [Run]. • The process takes several moments. Once Successfully finished appears in the output windows, click [View output] and then [Close]. • You may change the color of the vector to display it clearly on the raster background and to contrast with the original contour lines. You will notice that the new contour lines have smoother corners than the original while staying faithful to the original overall shape. Figure 16.12: GRASS module v.generalize to smooth a vector map Tip: Other uses for r.contour 16.9. The GRASS Toolbox 181 QGIS User Guide, Release 2.6 The procedure described above can be used in other equivalent situations. If you have a raster map of precipitation data, for example, then the same method will be used to create a vector map of isohyetal (constant rainfall) lines. Creating a Hillshade 3-D effect Several methods are used to display elevation layers and give a 3-D effect to maps. The use of contour lines, as shown above, is one popular method often chosen to produce topographic maps. Another way to display a 3-D effect is by hillshading. The hillshade effect is created from a DEM (elevation) raster by first calculating the slope and aspect of each cell, then simulating the sun’s position in the sky and giving a reflectance value to each cell. Thus, you get sun-facing slopes lighted; the slopes facing away from the sun (in shadow) are darkened. • Begin this example by loading the gtopo30 elevation raster. Start the GRASS Toolbox, and under the Raster category, double-click to open Spatial analysis → Terrain analysis. • Then click r.shaded.relief to open the module. • Change the azimuth angle 270 to 315. • Enter gtopo30_shade for the new hillshade raster, and click [Run]. • When the process completes, add the hillshade raster to the map. You should see it displayed in grayscale. • To view both the hillshading and the colors of the gtopo30 together, move the hillshade map below the gtopo30 map in the table of contents, then open the Properties window of gtopo30, switch to the Transparency tab and set its transparency level to about 25%. You should now have the gtopo30 elevation with its colormap and transparency setting displayed above the grayscale hillshade map. In order to see the visual effects of the hillshading, turn off the gtopo30_shade map, then turn it back on. Using the GRASS shell The GRASS plugin in QGIS is designed for users who are new to GRASS and not familiar with all the modules and options. As such, some modules in the Toolbox do not show all the options available, and some modules do not appear at all. The GRASS shell (or console) gives the user access to those additional GRASS modules that do not appear in the Toolbox tree, and also to some additional options to the modules that are in the Toolbox with the simplest default parameters. This example demonstrates the use of an additional option in the r.shaded.relief module that was shown above. The module r.shaded.relief can take a parameter zmult, which multiplies the elevation values relative to the X-Y coordinate units so that the hillshade effect is even more pronounced. • Load the gtopo30 elevation raster as above, then start the GRASS Toolbox and click on the GRASS shell. In the shell window, type the command r.shaded.relief map=gtopo30 shade=gtopo30_shade2 azimuth=315 zmult=3 and press [Enter]. • After the process finishes, shift to the Browse tab and double-click on the new gtopo30_shade2 raster to display it in QGIS. • As explained above, move the shaded relief raster below the gtopo30 raster in the table of contents, then check the transparency of the colored gtopo30 layer. You should see that the 3-D effect stands out more strongly compared with the first shaded relief map. Raster statistics in a vector map The next example shows how a GRASS module can aggregate raster data and add columns of statistics for each polygon in a vector map. • Again using the Alaska data, refer to Importing data into a GRASS LOCATION to import the trees shapefile from the shapefiles directory into GRASS. • Now an intermediate step is required: centroids must be added to the imported trees map to make it a complete GRASS area vector (including both boundaries and centroids). 182 Chapter 16. GRASS GIS Integration QGIS User Guide, Release 2.6 Figure 16.13: The GRASS shell, r.shaded.relief module Figure 16.14: Displaying shaded relief created with the GRASS module r.shaded.relief 16.9. The GRASS Toolbox 183 QGIS User Guide, Release 2.6 • From the Toolbox, choose Vector → Manage features, and open the module v.centroids. • Enter as the output vector map ‘forest_areas’ and run the module. • Now load the forest_areas vector and display the types of forests - deciduous, evergreen, mixed - in different colors: In the layer Properties window, Symbology tab, choose from Legend type ‘Unique value’ and set the Classification field to ‘VEGDESC’. (Refer to the explanation of the symbology tab in Style Menu of the vector section.) • Next, reopen the GRASS Toolbox and open Vector → Vector update by other maps. • Click on the v.rast.stats module. Enter gtopo30 and forest_areas. • Only one additional parameter is needed: Enter column prefix elev, and click [Run]. This is a computa- tionally heavy operation, which will run for a long time (probably up to two hours). • Finally, open the forest_areas attribute table, and verify that several new columns have been added, including elev_min, elev_max, elev_mean, etc., for each forest polygon. 16.9.3 Working with the GRASS LOCATION browser Another useful feature inside the GRASS Toolbox is the GRASS LOCATION browser. In figure_grass_module_7, you can see the current working LOCATION with its MAPSETs. In the left browser windows, you can browse through all MAPSETs inside the current LOCATION. The right browser window shows some meta-information for selected raster or vector layers (e.g., resolution, bounding box, data source, connected attribute table for vector data, and a command history). Figure 16.15: GRASS LOCATION browser The toolbar inside the Browser tab offers the following tools to manage the selected LOCATION: • Add selected map to canvas • Copy selected map • Rename selected map 184 Chapter 16. GRASS GIS Integration QGIS User Guide, Release 2.6 • Delete selected map • Set current region to selected map • Refresh browser window The Rename selected map and Delete selected map only work with maps inside your currently selected MAPSET. All other tools also work with raster and vector layers in another MAPSET. 16.9.4 Customizing the GRASS Toolbox Nearly all GRASS modules can be added to the GRASS Toolbox. An XML interface is provided to parse the pretty simple XML files that configure the modules’ appearance and parameters inside the Toolbox. A sample XML file for generating the module v.buffer (v.buffer.qgm) looks like this: The parser reads this definition and creates a new tab inside the Toolbox when you select the module. A more detailed description for adding new modules, changing a module’s group, etc., can be found on the QGIS wiki at http://hub.qgis.org/projects/quantum-gis/wiki/Adding_New_Tools_to_the_GRASS_Toolbox. . 16.9. The GRASS Toolbox 185 QGIS User Guide, Release 2.6 186 Chapter 16. GRASS GIS Integration CHAPTER 17 QGIS processing framework . 17.1 Introduction This chapter introduces the QGIS processing framework, a geoprocessing environment that can be used to call native and third-party algorithms from QGIS, making your spatial analysis tasks more productive and easy to accomplish. In the following sections, we will review how to use the graphical elements of this framework and make the most out of each one of them. There are four basic elements in the framework GUI, which are used to run algorithms for different purposes. Choosing one tool or another will depend on the kind of analysis that is to be performed and the particular characteristics of each user and project. All of them (except for the batch processing interface, which is called from the toolbox, as we will see) can be accessed from the Processing menu item. (You will see more than four entries. The remaining ones are not used to execute algorithms and will be explained later in this chapter.) • The toolbox. The main element of the GUI, it is used to execute a single algorithm or run a batch process based on that algorithm. Figure 17.1: Processing Toolbox 187 QGIS User Guide, Release 2.6 • The graphical modeler. Several algorithms can be combined graphically using the modeler to define a workflow, creating a single process that involves several subprocesses. Figure 17.2: Processing Modeler • The history manager. All actions performed using any of the aforementioned elements are stored in a history file and can be later easily reproduced using the history manager. • The batch processing interface. This interface allows you to execute batch processes and automate the execution of a single algorithm on multiple datasets. In the following sections, we will review each one of these elements in detail. . 17.2 The toolbox The Toolbox is the main element of the processing GUI, and the one that you are more likely to use in your daily work. It shows the list of all available algorithms grouped in different blocks, and it is the access point to run them, whether as a single process or as a batch process involving several executions of the same algorithm on different sets of inputs. The toolbox contains all the available algorithms, divided into predefined groups. All these groups are found under a single tree entry named Geoalgorithms. Additionally, two more entries are found, namely Models and Scripts. These include user-created algorithms, and they allow you to define your own workflows and processing tasks. We will devote a full section to them a bit later. In the upper part of the toolbox, you will find a text box. To reduce the number of algorithms shown in the toolbox and make it easier to find the one you need, you can enter any word or phrase on the text box. Notice that, as you type, the number of algorithms in the toolbox is reduced to just those that contain the text you have entered in their names. In the lower part, you will find a box that allows you to switch between the simplified algorithm list (the one explained above) and the advanced list. If you change to the advanced mode, the toolbox will look like this: 188 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 Figure 17.3: Processing History Figure 17.4: Batch Processing interface 17.2. The toolbox 189 QGIS User Guide, Release 2.6 Figure 17.5: Processing Toolbox Figure 17.6: Processing Toolbox (advanced mode) 190 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 In the advanced view, each group represents a so-called ‘algorithm provider’, which is a set of algorithms coming from the same source, for instance, from a third-party application with geoprocessing capabilities. Some of these groups represent algorithms from third-party applications like SAGA, GRASS or R, while others contain algorithms directly coded as part of the processing plugin, not relying on any additional software. This view is recommended to those users who have a certain knowledge of the applications that are backing the algorithms, since they will be shown with their original names and groups. Also, some additional algorithms are available only in the advanced view, such as LiDAR tools and scripts based on the R statistical computing software, among others. Independent QGIS plugins that add new algorithms to the toolbox will only be shown in the advanced view. In particular, the simplified view contains algorithms from the following providers: • GRASS • SAGA • OTB • Native QGIS algorithms In the case of running QGIS under Windows, these algorithms are fully-functional in a fresh installation of QGIS, and they can be run without requiring any additional installation. Also, running them requires no prior knowledge of the external applications they use, making them more accesible for first-time users. If you want to use an algorithm not provided by any of the above providers, switch to the advanced mode by selecting the corresponding option at the bottom of the toolbox. To execute an algorithm, just double-click on its name in the toolbox. 17.2.1 The algorithm dialog Once you double-click on the name of the algorithm that you want to execute, a dialog similar to that in the figure below is shown (in this case, the dialog corresponds to the SAGA ‘Convergence index’ algorithm). Figure 17.7: Parameters Dialog This dialog is used to set the input values that the algorithm needs to be executed. It shows a table where input values and configuration parameters are to be set. It of course has a different content, depending on the require- 17.2. The toolbox 191 QGIS User Guide, Release 2.6 ments of the algorithm to be executed, and is created automatically based on those requirements. On the left side, the name of the parameter is shown. On the right side, the value of the parameter can be set. Although the number and type of parameters depend on the characteristics of the algorithm, the structure is similar for all of them. The parameters found in the table can be of one of the following types. • A raster layer, to select from a list of all such layers available (currently opened) in QGIS. The selector contains as well a button on its right-hand side, to let you select filenames that represent layers currently not loaded in QGIS. • A vector layer, to select from a list of all vector layers available in QGIS. Layers not loaded in QGIS can be selected as well, as in the case of raster layers, but only if the algorithm does not require a table field selected from the attributes table of the layer. In that case, only opened layers can be selected, since they need to be open so as to retrieve the list of field names available. You will see a button by each vector layer selector, as shown in the figure below. Figure 17.8: Vector iterator button If the algorithm contains several of them, you will be able to toggle just one of them. If the button corresponding to a vector input is toggled, the algorithm will be executed iteratively on each one of its features, instead of just once for the whole layer, producing as many outputs as times the algorithm is executed. This allows for automating the process when all features in a layer have to be processed separately. • A table, to select from a list of all available in QGIS. Non-spatial tables are loaded into QGIS like vector layers, and in fact they are treated as such by the program. Currently, the list of available tables that you will see when executing an algorithm that needs one of them is restricted to tables coming from files in dBase (.dbf) or Comma-Separated Values (.csv) formats. • An option, to choose from a selection list of possible options. • A numerical value, to be introduced in a text box. You will find a button by its side. Clicking on it, you will see a dialog that allows you to enter a mathematical expression, so you can use it as a handy calculator. Some useful variables related to data loaded into QGIS can be added to your expression, so you can select a value derived from any of these variables, such as the cell size of a layer or the northernmost coordinate of another one. Figure 17.9: Number Selector • A range, with min and max values to be introduced in two text boxes. 192 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 • A text string, to be introduced in a text box. • A field, to choose from the attributes table of a vector layer or a single table selected in another parameter. • A coordinate reference system. You can type the EPSG code directly in the text box, or select it from the CRS selection dialog that appears when you click on the button on the right-hand side. • An extent, to be entered by four numbers representing its xmin, xmax, ymin, ymax limits. Clicking on the button on the right-hand side of the value selector, a pop-up menu will appear, giving you two options: to select the value from a layer or the current canvas extent, or to define it by dragging directly onto the map canvas. Figure 17.10: Extent selector If you select the first option, you will see a window like the next one. Figure 17.11: Extent List If you select the second one, the parameters window will hide itself, so you can click and drag onto the canvas. Once you have defined the selected rectangle, the dialog will reappear, containing the values in the extent text box. Figure 17.12: Extent Drag • A list of elements (whether raster layers, vector layers or tables), to select from the list of such layers available in QGIS. To make the selection, click on the small button on the left side of the corresponding row to see a dialog like the following one. • A small table to be edited by the user. These are used to define parameters like lookup tables or convolution kernels, among others. Click on the button on the right side to see the table and edit its values. 17.2. The toolbox 193 QGIS User Guide, Release 2.6 Figure 17.13: Multiple Selection Figure 17.14: Fixed Table 194 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 Depending on the algorithm, the number of rows can be modified or not by using the buttons on the right side of the window. You will find a [Help] tab in the the parameters dialog. If a help file is available, it will be shown, giving you more information about the algorithm and detailed descriptions of what each parameter does. Unfortunately, most algorithms lack good documentation, but if you feel like contributing to the project, this would be a good place to start. A note on projections Algorithms run from the processing framework — this is also true of most of the external applications whose algorithms are exposed through it. Do not perform any reprojection on input layers and assume that all of them are already in a common coordinate system and ready to be analized. Whenever you use more than one layer as input to an algorithm, whether vector or raster, it is up to you to make sure that they are all in the same coordinate system. Note that, due to QGIS‘s on-the-fly reprojecting capabilities, although two layers might seem to overlap and match, that might not be true if their original coordinates are used without reprojecting them onto a common coordinate system. That reprojection should be done manually, and then the resulting files should be used as input to the algorithm. Also, note that the reprojection process can be performed with the algorithms that are available in the processing framework itself. By default, the parameters dialog will show a description of the CRS of each layer along with its name, making it easy to select layers that share the same CRS to be used as input layers. If you do not want to see this additional information, you can disable this functionality in the processing configuration dialog, unchecking the Show CRS option. If you try to execute an algorithm using as input two or more layers with unmatching CRSs, a warning dialog will be shown. You still can execute the algorithm, but be aware that in most cases that will produce wrong results, such as empty layers due to input layers not overlapping. 17.2.2 Data objects generated by algorithms Data objects generated by an algorithm can be of any of the following types: • A raster layer • A vector layer • A table • An HTML file (used for text and graphical outputs) These are all saved to disk, and the parameters table will contain a text box corresponding to each one of these outputs, where you can type the output channel to use for saving it. An output channel contains the information needed to save the resulting object somewhere. In the most usual case, you will save it to a file, but the architecture allows for any other way of storing it. For instance, a vector layer can be stored in a database or even uploaded to a remote server using a WFS-T service. Although solutions like these are not yet implemented, the processing framework is prepared to handle them, and we expect to add new kinds of output channels in a near feature. To select an output channel, just click on the button on the right side of the text box. That will open a save file dialog, where you can select the desired file path. Supported file extensions are shown in the file format selector of the dialog, depending on the kind of output and the algorithm. The format of the output is defined by the filename extension. The supported formats depend on what is supported by the algorithm itself. To select a format, just select the corresponding file extension (or add it, if you are directly typing the file path instead). If the extension of the file path you entered does not match any of the supported formats, a default extension (usually .dbf‘ for tables, .tif for raster layers and .shp for vector layers) will be appended to the file path, and the file format corresponding to that extension will be used to save the layer or table. 17.2. The toolbox 195 QGIS User Guide, Release 2.6 If you do not enter any filename, the result will be saved as a temporary file in the corresponding default file format, and it will be deleted once you exit QGIS (take care with that, in case you save your project and it contains temporary layers). You can set a default folder for output data objects. Go to the configuration dialog (you can open it from the Processing menu), and in the General group, you will find a parameter named Output folder. This output folder is used as the default path in case you type just a filename with no path (i.e., myfile.shp) when executing an algorithm. When running an algorithm that uses a vector layer in iterative mode, the entered file path is used as the base path for all generated files, which are named using the base name and appending a number representing the index of the iteration. The file extension (and format) is used for all such generated files. Apart from raster layers and tables, algorithms also generate graphics and text as HTML files. These results are shown at the end of the algorithm execution in a new dialog. This dialog will keep the results produced by any algorithm during the current session, and can be shown at any time by selecting Processing → Results viewer from the QGIS main menu. Some external applications might have files (with no particular extension restrictions) as output, but they do not belong to any of the categories above. Those output files will not be processed by QGIS (opened or included into the current QGIS project), since most of the time they correspond to file formats or elements not supported by QGIS. This is, for instance, the case with LAS files used for LiDAR data. The files get created, but you won’t see anything new in your QGIS working session. For all the other types of output, you will find a checkbox that you can use to tell the algorithm whether to load the file once it is generated by the algorithm or not. By default, all files are opened. Optional outputs are not supported. That is, all outputs are created. However, you can uncheck the corresponding checkbox if you are not interested in a given output, which essentially makes it behave like an optional output (in other words, the layer is created anyway, but if you leave the text box empty, it will be saved to a temporary file and deleted once you exit QGIS). 17.2.3 Configuring the processing framework As has been mentioned, the configuration menu gives access to a new dialog where you can configure how algo- rithms work. Configuration parameters are structured in separate blocks that you can select on the left-hand side of the dialog. Along with the aforementioned Output folder entry, the General block contains parameters for setting the default rendering style for output layers (that is, layers generated by using algorithms from any of the framework GUI components). Just create the style you want using QGIS, save it to a file, and then enter the path to that file in the settings so the algorithms can use it. Whenever a layer is loaded by SEXTANTE and added to the QGIS canvas, it will be rendered with that style. Rendering styles can be configured individually for each algorithm and each one of its outputs. Just right-click on the name of the algorithm in the toolbox and select Edit rendering styles. You will see a dialog like the one shown next. Select the style file (.qml) that you want for each output and press [OK]. Other configuration parameters in the General group are listed below: • Use filename as layer name. The name of each resulting layer created by an algorithm is defined by the algorithm itself. In some cases, a fixed name might be used, meaning that the same output name will be used, no matter which input layer is used. In other cases, the name might depend on the name of the input layer or some of the parameters used to run the algorithm. If this checkbox is checked, the name will be taken from the output filename instead. Notice that, if the output is saved to a temporary file, the filename of this temporary file is usually a long and meaningless one intended to avoid collision with other already existing filenames. • Use only selected features. If this option is selected, whenever a vector layer is used as input for an al- gorithm, only its selected features will be used. If the layer has no selected features, all features will be used. 196 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 Figure 17.15: Rendering Styles • Pre-execution script file and Post-execution script file. These parameters refer to scripts written using the processing scripting functionality, and are explained in the section covering scripting and the console. Apart from the General block in the settings dialog, you will also find a block for algorithm providers. Each entry in this block contains an Activate item that you can use to make algorithms appear or not in the toolbox. Also, some algorithm providers have their own configuration items, which we will explain later when covering particular algorithm providers. . 17.3 The graphical modeler The graphical modeler allows you to create complex models using a simple and easy-to-use interface. When working with a GIS, most analysis operations are not isolated, but rather part of a chain of operations instead. Using the graphical modeler, that chain of processes can be wrapped into a single process, so it is as easy and convenient to execute as a single process later on a different set of inputs. No matter how many steps and different algorithms it involves, a model is executed as a single algorithm, thus saving time and effort, especially for larger models. The modeler can be opened from the processing menu. The modeler has a working canvas where the structure of the model and the workflow it represents are shown. On the left part of the window, a panel with two tabs can be used to add new elements to the model. Creating a model involves two steps: 1. Definition of necessary inputs. These inputs will be added to the parameters window, so the user can set their values when executing the model. The model itself is an algorithm, so the parameters window is generated automatically as it happens with all the algorithms available in the processing framework. 2. Definition of the workflow. Using the input data of the model, the workflow is defined by adding algorithms and selecting how they use those inputs or the outputs generated by other algorithms already in the model. 17.3.1 Definition of inputs The first step to create a model is to define the inputs it needs. The following elements are found in the Inputs tab on the left side of the modeler window: • Raster layer 17.3. The graphical modeler 197 QGIS User Guide, Release 2.6 Figure 17.16: Modeler • Vector layer • String • Table field • Table • Extent • Number • Boolean • File Double-clicking on any of these elements, a dialog is shown to define its characteristics. Depending on the parameter itself, the dialog may contain just one basic element (the description, which is what the user will see when executing the model) or more of them. For instance, when adding a numerical value, as can be seen in the next figure, apart from the description of the parameter, you have to set a default value and a range of valid values. For each added input, a new element is added to the modeler canvas. You can also add inputs by dragging the input type from the list and dropping it in the modeler canvas, in the position where you want to place it. 17.3.2 Definition of the workflow Once the inputs have been defined, it is time to define the algorithms to apply on them. Algorithms can be found in the Algorithms tab, grouped much in the same way as they are in the toolbox. The appearance of the toolbox has two modes here as well: simplified and advanced. However, there is no element to switch between views in the modeler, so you have to do it in the toolbox. The mode that is selected in the toolbox 198 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 Figure 17.17: Model Parameters Figure 17.18: Model Parameters Figure 17.19: Model Parameters 17.3. The graphical modeler 199 QGIS User Guide, Release 2.6 is the one that will be used for the list of algorithms in the modeler. To add an algorithm to a model, double-click on its name or drag and drop it, just like it was done when adding inputs. An execution dialog will appear, with a content similar to the one found in the execution panel that is shown when executing the algorithm from the toolbox. The one shown next corresponds to the SAGA ‘Convergence index’ algorithm, the same example we saw in the section dedicated to the toolbox. Figure 17.20: Model Parameters As you can see, some differences exist. Instead of the file output box that was used to set the file path for output layers and tables, a simple text box is used here. If the layer generated by the algorithm is just a temporary result that will be used as the input of another algorithm and should not be kept as a final result, just do not edit that text box. Typing anything in it means that the result is final and the text that you supply will be the description for the output, which will be the output the user will see when executing the model. Selecting the value of each parameter is also a bit different, since there are important differences between the context of the modeler and that of the toolbox. Let’s see how to introduce the values for each type of parameter. • Layers (raster and vector) and tables. These are selected from a list, but in this case, the possible values are not the layers or tables currently loaded in QGIS, but the list of model inputs of the corresponding type, or other layers or tables generated by algorithms already added to the model. • Numerical values. Literal values can be introduced directly in the text box. But this text box is also a list that can be used to select any of the numerical value inputs of the model. In this case, the parameter will take the value introduced by the user when executing the model. • String. As in the case of numerical values, literal strings can be typed, or an input string can be selected. • Table field. The fields of the parent table or layer cannot be known at design time, since they depend on the selection of the user each time the model is executed. To set the value for this parameter, type the name of a field directly in the text box, or use the list to select a table field input already added to the model. The validity of the selected field will be checked at run time. In all cases, you will find an additional parameter named Parent algorithms that is not available when calling the algorithm from the toolbox. This parameter allows you to define the order in which algorithms are executed by explicitly defining one algorithm as a parent of the current one, which will force the parent algorithm to be executed before the current one. When you use the output of a previous algorithm as the input of your algorithm, that implicitly sets the previous algorithm as parent of the current one (and places the corresponding arrow in the modeler canvas). However, 200 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 in some cases an algorithm might depend on another one even if it does not use any output object from it (for instance, an algorithm that executes an SQL sentence on a PostGIS database and another one that imports a layer into that same database). In that case, just select the previous algorithm in the Parent algorithms parameter and the two steps will be executed in the correct order. Once all the parameters have been assigned valid values, click on [OK] and the algorithm will be added to the canvas. It will be linked to all the other elements in the canvas, whether algorithms or inputs, that provide objects that are used as inputs for that algorithm. Elements can be dragged to a different position within the canvas, to change the way the module structure is displayed and make it more clear and intuitive. Links between elements are updated automatically. You can zoom in and out by using the mouse wheel. You can run your algorithm anytime by clicking on the [Run] button. However, in order to use the algorithm from the toolbox, it has to be saved and the modeler dialog closed, to allow the toolbox to refresh its contents. 17.3.3 Saving and loading models Use the [Save] button to save the current model and the [Open] button to open any model previously saved. Models are saved with the .model extension. If the model has been previously saved from the modeler window, you will not be prompted for a filename. Since there is already a file associated with that model, the same file will be used for any subsequent saves. Before saving a model, you have to enter a name and a group for it, using the text boxes in the upper part of the window. Models saved on the models folder (the default folder when you are prompted for a filename to save the model) will appear in the toolbox in the corresponding branch. When the toolbox is invoked, it searches the models folder for files with the .model extension and loads the models they contain. Since a model is itself an algorithm, it can be added to the toolbox just like any other algorithm. The models folder can be set from the processing configuration dialog, under the Modeler group. Models loaded from the models folder appear not only in the toolbox, but also in the algorithms tree in the Algorithms tab of the modeler window. That means that you can incorporate a model as a part of a bigger model, just as you add any other algorithm. In some cases, a model might not be loaded because not all the algorithms included in its workflow are available. If you have used a given algorithm as part of your model, it should be available (that is, it should appear in the toolbox) in order to load that model. Deactivating an algorithm provider in the processing configuration window renders all the algorithms in that provider unusable by the modeler, which might cause problems when loading models. Keep that in mind when you have trouble loading or executing models. 17.3.4 Editing a model You can edit the model you are currently creating, redefining the workflow and the relationships between the algorithms and inputs that define the model itself. If you right-click on an algorithm in the canvas representing the model, you will see a context menu like the one shown next: Figure 17.21: Modeler Right Click 17.3. The graphical modeler 201 QGIS User Guide, Release 2.6 Selecting the Remove option will cause the selected algorithm to be removed. An algorithm can be removed only if there are no other algorithms depending on it. That is, if no output from the algorithm is used in a different one as input. If you try to remove an algorithm that has others depending on it, a warning message like the one you can see below will be shown: Figure 17.22: Cannot Delete Algorithm Selecting the Edit option or simply double-clicking on the algorithm icon will show the parameters dialog of the algorithm, so you can change the inputs and parameter values. Not all input elements available in the model will appear in this case as available inputs. Layers or values generated at a more advanced step in the workflow defined by the model will not be available if they cause circular dependencies. Select the new values and then click on the [OK] button as usual. The connections between the model elements will change accordingly in the modeler canvas. 17.3.5 Editing model help files and meta-information You can document your models from the modeler itself. Just click on the [Edit model help] button and a dialog like the one shown next will appear. Figure 17.23: Help Edition On the right-hand side, you will see a simple HTML page, created using the description of the input parameters and outputs of the algorithm, along with some additional items like a general description of the model or its author. The first time you open the help editor, all these descriptions are empty, but you can edit them using the elements on the left-hand side of the dialog. Select an element on the upper part and then write its description in the text box below. Model help is saved in a file in the same folder as the model itself. You do not have to worry about saving it, since it is done automatically. 202 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 17.3.6 About available algorithms You might notice that some algorithms that can be be executed from the toolbox do not appear in the list of available algorithms when you are designing a model. To be included in a model, an algorithm must have a correct semantic, so as to be properly linked to others in the workflow. If an algorithm does not have such a well-defined semantic (for instance, if the number of output layers cannot be known in advance), then it is not possible to use it within a model, and thus, it does not appear in the list of algorithms that you can find in the modeler dialog. Additionally, you will see some algorithms in the modeler that are not found in the toolbox. These algorithms are meant to be used exclusively as part of a model, and they are of no interest in a different context. The ‘Calculator’ algorithm is an example of that. It is just a simple arithmetic calculator that you can use to modify numerical values (entered by the user or generated by some other algorithm). This tool is really useful within a model, but outside of that context, it doesn’t make too much sense. . 17.4 The batch processing interface 17.4.1 Introduction All algorithms (including models) can be executed as a batch process. That is, they can be executed using not just a single set of inputs, but several of them, executing the algorithm as many times as needed. This is useful when processing large amounts of data, since it is not necessary to launch the algorithm many times from the toolbox. To execute an algorithm as a batch process, right-click on its name in the toolbox and select the Execute as batch process option in the pop-up menu that will appear. Figure 17.24: Batch Processing Right Click 17.4.2 The parameters table Executing a batch process is similar to performing a single execution of an algorithm. Parameter values have to be defined, but in this case we need not just a single value for each parameter, but a set of them instead, one for each time the algorithm has to be executed. Values are introduced using a table like the one shown next. Each line of this table represents a single execution of the algorithm, and each cell contains the value of one of the parameters. It is similar to the parameters dialog that you see when executing an algorithm from the toolbox, but with a different arrangement. By default, the table contains just two rows. You can add or remove rows using the buttons on the lower part of the window. Once the size of the table has been set, it has to be filled with the desired values. 17.4.3 Filling the parameters table For most parameters, setting the value is trivial. Just type the value or select it from the list of available options, depending on the parameter type. The main differences are found for parameters representing layers or tables, and for output file paths. Regarding input layers and tables, when an algorithm is executed as part of a batch process, those input data objects are taken directly from files, and not from the set of them already opened in QGIS. For this reason, any algorithm can be 17.4. The batch processing interface 203 QGIS User Guide, Release 2.6 Figure 17.25: Batch Processing executed as a batch process, even if no data objects at all are opened and the algorithm cannot be run from the toolbox. Filenames for input data objects are introduced directly typing or, more conveniently, clicking on the button on the right hand of the cell, which shows a typical file chooser dialog. Multiple files can be selected at once. If the input parameter represents a single data object and several files are selected, each one of them will be put in a separate row, adding new ones if needed. If the parameter represents a multiple input, all the selected files will be added to a single cell, separated by semicolons (;). Output data objects are always saved to a file and, unlike when executing an algorithm from the toolbox, saving to a temporary file is not permitted. You can type the name directly or use the file chooser dialog that appears when clicking on the accompanying button. Once you select the file, a new dialog is shown to allow for autocompletion of other cells in the same column (same parameter). Figure 17.26: Batch Processing Save If the default value (‘Do not autocomplete’) is selected, it will just put the selected filename in the selected cell from the parameters table. If any of the other options is selected, all the cells below the selected one will be automatically filled based on a defined criteria. This way, it is much easier to fill the table, and the batch process can be defined with less effort. Automatic filling can be done by simply adding correlative numbers to the selected file path, or by appending the value of another field at the same row. This is particularly useful for naming output data objects according to input 204 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 ones. Figure 17.27: Batch Processing File Path 17.4.4 Executing the batch process To execute the batch process once you have introduced all the necessary values, just click on [OK]. Progress of the global batch task will be shown in the progress bar in the lower part of the dialog. . 17.5 Using processing algorithms from the console The console allows advanced users to increase their productivity and perform complex operations that cannot be performed using any of the other GUI elements of the processing framework. Models involving several algorithms can be defined using the command-line interface, and additional operations such as loops and conditional sentences can be added to create more flexible and powerful workflows. There is not a proccesing console in QGIS, but all processing commands are available instead from the QGIS built-in Python console. That means that you can incorporate those commands into your console work and connect processing algorithms to all the other features (including methods from the QGIS API) available from there. The code that you can execute from the Python console, even if it does not call any specific processing method, can be converted into a new algorithm that you can later call from the toolbox, the graphical modeler or any other component, just like you do with any other algorithm. In fact, some algorithms that you can find in the toolbox are simple scripts. In this section, we will see how to use processing algorithms from the QGIS Python console, and also how to write algorithms using Python. 17.5.1 Calling algorithms from the Python console The first thing you have to do is to import the processing functions with the following line: >>> import processing Now, there is basically just one (interesting) thing you can do with that from the console: execute an algorithm. That is done using the runalg() method, which takes the name of the algorithm to execute as its first parameter, and then a variable number of additional parameters depending on the requirements of the algorithm. So the first thing you need to know is the name of the algorithm to execute. That is not the name you see in the toolbox, but rather a unique command–line name. To find the right name for your algorithm, you can use the algslist() method. Type the following line in your console: >>> processing.alglist() You will see something like this. Accumulated Cost (Anisotropic)---------------->saga:accumulatedcost(anisotropic) Accumulated Cost (Isotropic)------------------>saga:accumulatedcost(isotropic) Add Coordinates to points--------------------->saga:addcoordinatestopoints Add Grid Values to Points--------------------->saga:addgridvaluestopoints Add Grid Values to Shapes--------------------->saga:addgridvaluestoshapes Add Polygon Attributes to Points-------------->saga:addpolygonattributestopoints 17.5. Using processing algorithms from the console 205 QGIS User Guide, Release 2.6 Aggregate------------------------------------->saga:aggregate Aggregate Point Observations------------------>saga:aggregatepointobservations Aggregation Index----------------------------->saga:aggregationindex Analytical Hierarchy Process------------------>saga:analyticalhierarchyprocess Analytical Hillshading------------------------>saga:analyticalhillshading Average With Mask 1--------------------------->saga:averagewithmask1 Average With Mask 2--------------------------->saga:averagewithmask2 Average With Thereshold 1--------------------->saga:averagewiththereshold1 Average With Thereshold 2--------------------->saga:averagewiththereshold2 Average With Thereshold 3--------------------->saga:averagewiththereshold3 B-Spline Approximation------------------------>saga:b-splineapproximation ... That’s a list of all the available algorithms, alphabetically ordered, along with their corresponding command-line names. You can use a string as a parameter for this method. Instead of returning the full list of algorithms, it will only display those that include that string. If, for instance, you are looking for an algorithm to calculate slope from a DEM, type alglist("slope") to get the following result: DTM Filter (slope-based)---------------------->saga:dtmfilter(slope-based) Downslope Distance Gradient------------------->saga:downslopedistancegradient Relative Heights and Slope Positions---------->saga:relativeheightsandslopepositions Slope Length---------------------------------->saga:slopelength Slope, Aspect, Curvature---------------------->saga:slopeaspectcurvature Upslope Area---------------------------------->saga:upslopearea Vegetation Index[slope based]----------------->saga:vegetationindex[slopebased] This result might change depending on the algorithms you have available. It is easier now to find the algorithm you are looking for and its command-line name, in this case saga:slopeaspectcurvature. Once you know the command-line name of the algorithm, the next thing to do is to determine the right syntax to execute it. That means knowing which parameters are needed and the order in which they have to be passed when calling the runalg() method. There is a method to describe an algorithm in detail, which can be used to get a list of the parameters that an algorithm requires and the outputs that it will generate. To get this information, you can use the alghelp(name_of_the_algorithm) method. Use the command-line name of the algorithm, not the full descriptive name. Calling the method with saga:slopeaspectcurvature as parameter, you get the following description: >>> processing.alghelp("saga:slopeaspectcurvature") ALGORITHM: Slope, Aspect, Curvature ELEVATION METHOD SLOPE ASPECT CURV HCURV VCURV Now you have everything you need to run any algorithm. As we have already mentioned, there is only one single command to execute algorithms: runalg(). Its syntax is as follows: >>> processing.runalg(name_of_the_algorithm, param1, param2,..., paramN, Output1, Output2, ..., OutputN) The list of parameters and outputs to add depends on the algorithm you want to run, and is exactly the list that the alghelp() method gives you, in the same order as shown. Depending on the type of parameter, values are introduced differently. The next list gives a quick review of how to introduce values for each type of input parameter: 206 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 • Raster Layer, Vector Layer or Table. Simply use a string with the name that identifies the data object to use (the name it has in the QGIS Table of Contents) or a filename (if the corresponding layer is not opened, it will be opened but not added to the map canvas). If you have an instance of a QGIS object representing the layer, you can also pass it as parameter. If the input is optional and you do not want to use any data object, use None. • Selection. If an algorithm has a selection parameter, the value of that parameter should be entered using an integer value. To know the available options, you can use the algoptions() command, as shown in the following example: >>> processing.algoptions("saga:slopeaspectcurvature") METHOD(Method) 0 - [0] Maximum Slope (Travis et al. 1975) 1 - [1] Maximum Triangle Slope (Tarboton 1997) 2 - [2] Least Squares Fitted Plane (Horn 1981, Costa-Cabral & Burgess 1996) 3 - [3] Fit 2.Degree Polynom (Bauer, Rohdenburg, Bork 1985) 4 - [4] Fit 2.Degree Polynom (Heerdegen & Beran 1982) 5 - [5] Fit 2.Degree Polynom (Zevenbergen & Thorne 1987) 6 - [6] Fit 3.Degree Polynom (Haralick 1983) In this case, the algorithm has one such parameter, with seven options. Notice that ordering is zero-based. • Multiple input. The value is a string with input descriptors separated by semicolons (;). As in the case of single layers or tables, each input descriptor can be the data object name, or its file path. • Table Field from XXX. Use a string with the name of the field to use. This parameter is case-sensitive. • Fixed Table. Type the list of all table values separated by commas (,) and enclosed between quotes ("). Values start on the upper row and go from left to right. You can also use a 2-D array of values representing the table. • CRS. Enter the EPSG code number of the desired CRS. • Extent. You must use a string with xmin, xmax, ymin and ymax values separated by commas (,). Boolean, file, string and numerical parameters do not need any additional explanations. Input parameters such as strings, booleans, or numerical values have default values. To use them, specify None in the corresponding parameter entry. For output data objects, type the file path to be used to save it, just as it is done from the toolbox. If you want to save the result to a temporary file, use None. The extension of the file determines the file format. If you enter a file extension not supported by the algorithm, the default file format for that output type will be used, and its corresponding extension appended to the given file path. Unlike when an algorithm is executed from the toolbox, outputs are not added to the map canvas if you execute that same algorithm from the Python console. If you want to add an output to the map canvas, you have to do it yourself after running the algorithm. To do so, you can use QGIS API commands, or, even easier, use one of the handy methods provided for such tasks. The runalg method returns a dictionary with the output names (the ones shown in the algorithm description) as keys and the file paths of those outputs as values. You can load those layers by passing the corresponding file paths to the load() method. 17.5.2 Additional functions for handling data Apart from the functions used to call algorithms, importing the processing package will also import some additional functions that make it easier to work with data, particularly vector data. They are just convenience functions that wrap some functionality from the QGIS API, usually with a less complex syntax. These functions should be used when developing new algorithms, as they make it easier to operate with input data. Below is a list of some of these commands. More information can be found in the classes under the processing/tools package, and also in the example scripts provided with QGIS. 17.5. Using processing algorithms from the console 207 QGIS User Guide, Release 2.6 • getObject(obj): Returns a QGIS object (a layer or table) from the passed object, which can be a filename or the name of the object in the QGIS Table of Contents. • values(layer, fields): Returns the values in the attributes table of a vector layer, for the passed fields. Fields can be passed as field names or as zero-based field indices. Returns a dict of lists, with the passed field identifiers as keys. It considers the existing selection. • features(layer): Returns an iterator over the features of a vector layer, considering the existing selection. • uniqueValues(layer, field): Returns a list of unique values for a given attribute. Attributes can be passed as a field name or a zero-based field index. It considers the existing selection. 17.5.3 Creating scripts and running them from the toolbox You can create your own algorithms by writing the corresponding Python code and adding a few extra lines to supply additional information needed to define the semantics of the algorithm. You can find a Create new script menu under the Tools group in the Script algorithms block of the toolbox. Double-click on it to open the script editing dialog. That’s where you should type your code. Saving the script from there in the scripts folder (the default folder when you open the save file dialog) with .py extension will automatically create the corresponding algorithm. The name of the algorithm (the one you will see in the toolbox) is created from the filename, removing its extension and replacing low hyphens with blank spaces. Let’s have a look at the following code, which calculates the Topographic Wetness Index (TWI) directly from a DEM. ##dem=raster ##twi=output ret_slope = processing.runalg("saga:slopeaspectcurvature", dem, 0, None, None, None, None, None) ret_area = processing.runalg("saga:catchmentarea(mass-fluxmethod)", dem, 0, False, False, False, False, None, None, None, None, None) processing.runalg("saga:topographicwetnessindex(twi), ret_slope[’SLOPE’], ret_area[’AREA’], None, 1, 0, twi) As you can see, the calculation involves three algorithms, all of them coming from SAGA. The last one calculates the TWI, but it needs a slope layer and a flow accumulation layer. We do not have these layers, but since we have the DEM, we can calculate them by calling the corresponding SAGA algorithms. The part of the code where this processing takes place is not difficult to understand if you have read the previous sections in this chapter. The first lines, however, need some additional explanation. They provide the information that is needed to turn your code into an algorithm that can be run from any of the GUI components, like the toolbox or the graphical modeler. These lines start with a double Python comment symbol (##) and have the following structure: [parameter_name]=[parameter_type] [optional_values] Here is a list of all the parameter types that are supported in processing scripts, their syntax and some examples. • raster. A raster layer. • vector. A vector layer. • table. A table. • number. A numerical value. A default value must be provided. For instance, depth=number 2.4. • string. A text string. As in the case of numerical values, a default value must be added. For instance, name=string Victor. • boolean. A boolean value. Add True or False after it to set the default value. For example, verbose=boolean True. 208 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 • multiple raster. A set of input raster layers. • multiple vector. A set of input vector layers. • field. A field in the attributes table of a vector layer. The name of the layer has to be added after the field tag. For instance, if you have declared a vector input with mylayer=vector, you could use myfield=field mylayer to add a field from that layer as parameter. • folder. A folder. • file. A filename. The parameter name is the name that will be shown to the user when executing the algorithm, and also the variable name to use in the script code. The value entered by the user for that parameter will be assigned to a variable with that name. When showing the name of the parameter to the user, the name will be edited to improve its appearance, replacing low hyphens with spaces. So, for instance, if you want the user to see a parameter named A numerical value, you can use the variable name A_numerical_value. Layers and table values are strings containing the file path of the corresponding object. To turn them into a QGIS object, you can use the processing.getObjectFromUri() function. Multiple inputs also have a string value, which contains the file paths to all selected object, separated by semicolons (;). Outputs are defined in a similar manner, using the following tags: • output raster • output vector • output table • output html • output file • output number • output string The value assigned to the output variables is always a string with a file path. It will correspond to a temporary file path in case the user has not entered any output filename. When you declare an output, the algorithm will try to add it to QGIS once it is finished. That is why, although the runalg() method does not load the layers it produces, the final TWI layer will be loaded (using the case of our previous example), since it is saved to the file entered by the user, which is the value of the corresponding output. Do not use the load() method in your script algorithms, just when working with the console line. If a layer is created as output of an algorithm, it should be declared as such. Otherwise, you will not be able to properly use the algorithm in the modeler, since its syntax (as defined by the tags explained above) will not match what the algorithm really creates. Hidden outputs (numbers and strings) do not have a value. Instead, you have to assign a value to them. To do so, just set the value of a variable with the name you used to declare that output. For instance, if you have used this declaration, ##average=output number the following line will set the value of the output to 5: average=5 In addition to the tags for parameters and outputs, you can also define the group under which the algorithm will be shown, using the group tag. If your algorithm takes a long time to process, it is a good idea to inform the user. You have a global named progress available, with two possible methods: setText(text) and setPercentage(percent) to modify the progress text and the progress bar. 17.5. Using processing algorithms from the console 209 QGIS User Guide, Release 2.6 Several examples are provided. Please check them to see real examples of how to create algorithms using the processing framework classes. You can right-click on any script algorithm and select Edit script to edit its code or just to see it. 17.5.4 Documenting your scripts As in the case of models, you can create additional documentation for your scripts, to explain what they do and how to use them. In the script editing dialog, you will find an [Edit script help] button. Click on it and it will take you to the help editing dialog. Check the section about the graphical modeler to know more about this dialog and how to use it. Help files are saved in the same folder as the script itself, adding the .help extension to the filename. Notice that you can edit your script’s help before saving the script for the first time. If you later close the script editing dialog without saving the script (i.e., you discard it), the help content you wrote will be lost. If your script was already saved and is associated to a filename, saving the help content is done automatically. 17.5.5 Pre- and post-execution script hooks Scripts can also be used to set pre- and post-execution hooks that are run before and after an algorithm is run. This can be used to automate tasks that should be performed whenever an algorithm is executed. The syntax is identical to the syntax explained above, but an additional global variable named alg is available, representing the algorithm that has just been (or is about to be) executed. In the General group of the processing configuration dialog, you will find two entries named Pre-execution script file and Post-execution script file where the filename of the scripts to be run in each case can be entered. . 17.6 The history manager 17.6.1 The processing history Every time you execute an algorithm, information about the process is stored in the history manager. Along with the parameters used, the date and time of the execution are also saved. This way, it is easy to track and control all the work that has been developed using the processing framework, and easily reproduce it. The history manager is a set of registry entries grouped according to their date of execution, making it easier to find information about an algorithm executed at any particular moment. Process information is kept as a command-line expression, even if the algorithm was launched from the toolbox. This makes it also useful for those learning how to use the command-line interface, since they can call an algorithm using the toolbox and then check the history manager to see how that same algorithm could be called from the command line. Apart from browsing the entries in the registry, you can also re-execute processes by simply double-clicking on the corresponding entry. Along with recording algorithm executions, the processing framework communicates with the user by means of the other groups of the registry, namely Errors, Warnings and Information. In case something is not working properly, having a look at the Errors might help you to see what is happening. If you get in contact with a developer to report a bug or error, the information in that group will be very useful for her or him to find out what is going wrong. Third-party algorithms are usually executed by calling their command-line interfaces, which communicate with the user via the console. Although that console is not shown, a full dump of it is stored in the Information group each time you run one of those algorithms. If, for instance, you are having problems executing a SAGA algorithm, 210 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 Figure 17.28: History look for an entry named ‘SAGA execution console output’ to check all the messages generated by SAGA and try to find out where the problem is. Some algorithms, even if they can produce a result with the given input data, might add comments or additional information to the Warning block if they detect potential problems with the data, in order to warn you. Make sure you check those messages if you are having unexpected results. 17.7 Writing new Processing algorithms as python scripts You can create your own algorithms by writing the corresponding Python code and adding a few extra lines to supply additional information needed to define the semantics of the algorithm. You can find a Create new script menu under the Tools group in the Script algorithms block of the toolbox. Double-click on it to open the script edition dialog. That’s where you should type your code. Saving the script from there in the scripts folder (the default one when you open the save file dialog), with .py extension, will automatically create the corresponding algorithm. The name of the algorithm (the one you will see in the toolbox) is created from the filename, removing its extension and replacing low hyphens with blank spaces. Let’s have the following code, which calculates the Topographic Wetness Index (TWI) directly from a DEM ##dem=raster ##twi=output raster ret_slope = processing.runalg("saga:slopeaspectcurvature", dem, 0, None, None, None, None, None) ret_area = processing.runalg("saga:catchmentarea", dem, 0, False, False, False, False, None, None, None, None, None) processing.runalg("saga:topographicwetnessindextwi, ret_slope[’SLOPE’], ret_area[’AREA’], None, 1, 0, twi) As you can see, it involves 3 algorithms, all of them coming from SAGA. The last one of them calculates the TWI, but it needs a slope layer and a flow accumulation layer. We do not have these ones, but since we have the DEM, 17.7. Writing new Processing algorithms as python scripts 211 QGIS User Guide, Release 2.6 we can calculate them calling the corresponding SAGA algorithms. The part of the code where this processing takes place is not difficult to understand if you have read the previous chapter. The first lines, however, need some additional explanation. They provide the information that is needed to turn your code into an algorithm that can be run from any of the GUI components, like the toolbox or the graphical modeler. These lines start with a double Python comment symbol (##) and have the following structure [parameter_name]=[parameter_type] [optional_values] Here is a list of all the parameter types that are supported in processign scripts, their syntax and some examples. • raster. A raster layer • vector. A vector layer • table. A table • number. A numerical value. A default value must be provided. For instance, depth=number 2.4 • string. A text string. As in the case of numerical values, a default value must be added. For instance, name=string Victor • longstring. Same as string, but a larger text box will be shown, so it is better suited for long strings, such as for a script expecting a small code snippet. • boolean. A boolean value. Add True or False after it to set the default value. For example, verbose=boolean True. • multiple raster. A set of input raster layers. • multiple vector. A set of input vector layers. • field. A field in the attributes table of a vector layer. The name of the layer has to be added after the field tag. For instance, if you have declared a vector input with mylayer=vector, you could use myfield=field mylayer to add a field from that layer as parameter. • folder. A folder • file. A filename • crs. A Coordinate Reference System The parameter name is the name that will be shown to the user when executing the algorithm, and also the variable name to use in the script code. The value entered by the user for that parameter will be assigned to a variable with that name. When showing the name of the parameter to the user, the name will be edited it to improve its appearance, replacing low hyphens with spaces. So, for instance, if you want the user to see a parameter named A numerical value, you can use the variable name A_numerical_value. Layers and tables values are strings containing the filepath of the corresponding object. To turn them into a QGIS object, you can use the processing.getObjectFromUri() function. Multiple inputs also have a string value, which contains the filepaths to all selected objects, separated by semicolons (;). Outputs are defined in a similar manner, using the following tags: • output raster • output vector • output table • output html • output file • output number • output string 212 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 • output extent The value assigned to the output variables is always a string with a filepath. It will correspond to a temporary filepath in case the user has not entered any output filename. In addition to the tags for parameters and outputs, you can also define the group under which the algorithm will be shown, using the group tag. The last tag that you can use in your script header is ##nomodeler. Use that when you do not want your algorithm to be shown in the modeler window. This should be used for algorithms that do not have a clear syntax (for instance, if the number of layers to be created is not known in advance, at design time), which make them unsuitable for the graphical modeler 17.8 Handing data produced by the algorithm When you declare an output representing a layer (raster, vector or table), the algorithm will try to add it to QGIS once it is finished. That is the reason why, although the runalg() method does not load the layers it produces, the final TWI layer will be loaded, since it is saved to the file entered by the user, which is the value of the corresponding output. Do not use the load() method in your script algorithms, but just when working with the console line. If a layer is created as output of an algorithm, it should be declared as such. Otherwise, you will not be able to properly use the algorithm in the modeler, since its syntax (as defined by the tags explained above) will not match what the algorithm really creates. Hidden outputs (numbers and strings) do not have a value. Instead, it is you who has to assign a value to them. To do so, just set the value of a variable with the name you used to declare that output. For instance, if you have used this declaration, ##average=output number the following line will set the value of the output to 5: average=5 17.9 Communicating with the user If your algorithm takes a long time to process, it is a good idea to inform the user. You have a global named progress available, with two available methods: setText(text) and setPercentage(percent) to modify the progress text and the progress bar. If you have to provide some information to the user, not related to the progress of the algorithm, you can use the setInfo(text) method, also from the progress object. If your script has some problem, the correct way of propagating it is to raise an exception of type GeoAlgorithmExecutionException(). You can pass a message as argument to the constructor of the exception. Processing will take care of handling it and communicating with the user, depending on where the algorithm is being executed from (toolbox, modeler, Python console...) 17.10 Documenting your scripts As in the case of models, you can create additional documentation for your script, to explain what they do and how to use them. In the script editing dialog you will find a [Edit script help] button. Click on it and it will take you to the help editing dialog. Check the chapter about the graphical modeler to know more about this dialog and how to use it. Help files are saved in the same folder as the script itself, adding the .help extension to the filename. Notice that you can edit your script’s help before saving it for the first time. If you later close the script editing dialog without 17.8. Handing data produced by the algorithm 213 QGIS User Guide, Release 2.6 saving the script (i.e. you discard it), the help content you wrote will be lost. If your script was already saved and is associated to a filename, saving is done automatically. 17.11 Example scripts Several examples are available in the on-line collection of scripts, which you can access by selecting the Get script from on-line script collection tool under the Scripts/tools entry in the toolbox. Please, check them to see real examples of how to create algorithms using the processing framework classes. You can right-click on any script algorithm and select Edit script to edit its code or just to see it. 17.12 Best practices for writing script algorithms Here’s a quick summary of ideas to consider when creating your script algorithms and, epsecially, if you want to share with other QGIS users. Following these simple rules will ensure consistency across the different Processing elements such as the toolbox, the modeler or the batch processing interface. • Do not load resulting layers. Let Processing handle your results and load your layers if needed. • Always declare the outputs your algorithm creates. Avoid things such as decalring one output and then using the destination filename set for that output to create a collection of them. That will break the correct semantics of the algorithm and make it impossible to use it safely in the modeler. If you have to write an algorithm like that, make sure you add the ##nomodeler tag. • Do not show message boxes or use any GUI element from the script. If you want to communicate with the user, use the setInfo() method or throw an GeoAlgorithmExecutionException • As a rule of thumb, do not forget that your agorithm might be executed in a context other than the Processing toolbox. 17.13 Pre- and post-execution script hooks Scripts can also be used to set pre- and post-execution hooks that are run before and after an algorithm is run. This can be used to automate tasks that should be performed whenever an algorithm is executed. The syntax is identical to the syntax explained above, but an additional global variable named alg is available, representing the algorithm that has just been (or is about to be) executed. In the General group of the processing config dialog you will find two entries named Pre-execution script file and Post-execution script file where the filename of the scripts to be run in each case can be entered. . 17.14 Configuring external applications The processing framework can be extended using additional applications. Currently, SAGA, GRASS, OTB (Orfeo Toolbox) and R are supported, along with some other command-line applications that provide spatial data analysis functionalities. Algorithms relying on an external application are managed by their own algorithm provider. 214 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 This section will show you how to configure the processing framework to include these additional applications, and it will explain some particular features of the algorithms based on them. Once you have correctly configured the system, you will be able to execute external algorithms from any component like the toolbox or the graphical modeler, just like you do with any other geoalgorithm. By default, all algorithms that rely on an external appplication not shipped with QGIS are not enabled. You can enable them in the configuration dialog. Make sure that the corresponding application is already installed in your system. Enabling an algorithm provider without installing the application it needs will cause the algorithms to appear in the toolbox, but an error will be thrown when you try to execute them. This is because the algorithm descriptions (needed to create the parameters dialog and provide the information needed about the algorithm) are not included with each application, but with QGIS instead. That is, they are part of QGIS, so you have them in your installation even if you have not installed any other software. Running the algorithm, however, needs the application binaries to be installed in your system. 17.14.1 A note for Windows users If you are not an advanced user and you are running QGIS on Windows, you might not be interested in reading the rest of this chapter. Make sure you install QGIS in your system using the standalone installer. That will automatically install SAGA, GRASS and OTB in your system and configure them so they can be run from QGIS. All the algorithms in the simplified view of the toolbox will be ready to be run without needing any further configuration. If installing through OSGeo4W application, make sure you select for insttallation SAGA and OTB as well. If you want to know more about how these providers work, or if you want to use some algorithms not included in the simplified toolbox (such as R scripts), keep on reading. 17.14.2 A note on file formats When using an external software, opening a file in QGIS does not mean that it can be opened and processed as well in that other software. In most cases, other software can read what you have opened in QGIS, but in some cases, that might not be true. When using databases or uncommon file formats, whether for raster or vector layers, problems might arise. If that happens, try to use well-known file formats that you are sure are understood by both programs, and check the console output (in the history and log dialog) to know more about what is going wrong. Using GRASS raster layers is, for instance, one case in which you might have trouble and not be able to complete your work if you call an external algorithm using such a layer as input. For this reason, these layers will not appear as available to algorithms. You should, however, find no problems at all with vector layers, since QGIS automatically converts from the original file format to one accepted by the external application before passing the layer to it. This adds extra processing time, which might be significant if the layer has a large size, so do not be surprised if it takes more time to process a layer from a DB connection than it does to process one of a similar size stored in a shapefile. Providers not using external applications can process any layer that you can open in QGIS, since they open it for analysis through QGIS. Regarding output formats, all formats supported by QGIS as output can be used, both for raster and vector layers. Some providers do not support certain formats, but all can export to common raster layer formats that can later be transformed by QGIS automatically. As in the case of input layers, if this conversion is needed, that might increase the processing time. If the extension of the filename specified when calling an algorithm does not match the extension of any of the formats supported by QGIS, then a suffix will be added to set a default format. In the case of raster layers, the .tif extension is used, while .shp is used for vector layers. 17.14.3 A note on vector layer selections External applications may also be made aware of the selections that exist in vector layers within QGIS. However, that requires rewriting all input vector layers, just as if they were originally in a format not supported by the 17.14. Configuring external applications 215 QGIS User Guide, Release 2.6 external application. Only when no selection exists, or the Use only selected features option is not enabled in the processing general configuration, can a layer be directly passed to an external application. In other cases, exporting only selected features is needed, which causes execution times to be longer. SAGA SAGA algorithms can be run from QGIS if you have SAGA installed in your system and you configure the pro- cessing framework properly so it can find SAGA executables. In particular, the SAGA command-line executable is needed to run SAGA algorithms. If you are running Windows, both the stand-alone installer and the OSGeo4W installer include SAGA along with QGIS, and the path is automatically configured, so there is no need to do anything else. If you have installed SAGA yourself (remember, you need version 2.1), the path to the SAGA executable must be configured. To do this, open the configuration dialog. In the SAGA block, you will find a setting named SAGA Folder. Enter the path to the folder where SAGA is installed. Close the configuration dialog, and now you are ready to run SAGA algorithms from QGIS. If you are running Linux, SAGA binaries are not included with SEXTANTE, so you have to download and install the software yourself. Please check the SAGA website for more information. SAGA 2.1 is needed. In this case, there is no need to configure the path to the SAGA executable, and you will not see those folders. Instead, you must make sure that SAGA is properly installed and its folder is added to the PATH environment variable. Just open a console and type saga_cmd to check that the system can find where the SAGA binaries are located. 17.14.4 About SAGA grid system limitations Most SAGA algorithms that require several input raster layers require them to have the same grid system. That is, they must cover the same geographic area and have the same cell size, so their corresponding grids match. When calling SAGA algorithms from QGIS, you can use any layer, regardless of its cell size and extent. When multiple raster layers are used as input for a SAGA algorithm, QGIS resamples them to a common grid system and then passes them to SAGA (unless the SAGA algorithm can operate with layers from different grid systems). The definition of that common grid system is controlled by the user, and you will find several parameters in the SAGA group of the settings window to do so. There are two ways of setting the target grid system: • Setting it manually. You define the extent by setting the values of the following parameters: – Resampling min X – Resampling max X – Resampling min Y – Resampling max Y – Resampling cellsize Notice that QGIS will resample input layers to that extent, even if they do not overlap with it. • Setting it automatically from input layers. To select this option, just check the Use min covering grid system for resampling option. All the other settings will be ignored and the minimum extent that covers all the input layers will be used. The cell size of the target layer is the maximum of all cell sizes of the input layers. For algorithms that do not use multiple raster layers, or for those that do not need a unique input grid system, no resampling is performed before calling SAGA, and those parameters are not used. 17.14.5 Limitations for multi-band layers Unlike QGIS, SAGA has no support for multi-band layers. If you want to use a multiband layer (such as an RGB or multispectral image), you first have to split it into single-banded images. To do so, you can use the ‘SAGA/Grid 216 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 - Tools/Split RGB image’ algorithm (which creates three images from an RGB image) or the ‘SAGA/Grid - Tools/Extract band’ algorithm (to extract a single band). 17.14.6 Limitations in cell size SAGA assumes that raster layers have the same cell size in the X and Y axis. If you are working with a layer with different values for horizontal and vertical cell size, you might get unexpected results. In this case, a warning will be added to the processing log, indicating that an input layer might not be suitable to be processed by SAGA. 17.14.7 Logging When QGIS calls SAGA, it does so using its command-line interface, thus passing a set of commands to perform all the required operations. SAGA shows its progress by writing information to the console, which includes the percentage of processing already done, along with additional content. This output is filtered and used to update the progress bar while the algorithm is running. Both the commands sent by QGIS and the additional information printed by SAGA can be logged along with other processing log messages, and you might find them useful to track in detail what is going on when QGIS runs a SAGA algorithm. You will find two settings, namely Log console output and Log execution commands, to activate that logging mechanism. Most other providers that use an external application and call it through the command-line have similar options, so you will find them as well in other places in the processing settings list. R. Creating R scripts R integration in QGIS is different from that of SAGA in that there is not a predefined set of algorithms you can run (except for a few examples). Instead, you should write your scripts and call R commands, much like you would do from R, and in a very similar manner to what we saw in the section dedicated to processing scripts. This section shows you the syntax to use to call those R commands from QGIS and how to use QGIS objects (layers, tables) in them. The first thing you have to do, as we saw in the case of SAGA, is to tell QGIS where your R binaries are located. You can do this using the R folder entry in the processing configuration dialog. Once you have set that parameter, you can start creating and executing your own R scripts. Once again, this is different in Linux, and you just have to make sure that the R folder is included in the PATH environment variable. If you can start R just typing R in a console, then you are ready to go. To add a new algorithm that calls an R function (or a more complex R script that you have developed and you would like to have available from QGIS), you have to create a script file that tells the processing framework how to perform that operation and the corresponding R commands to do so. R script files have the extension .rsx, and creating them is pretty easy if you just have a basic knowledge of R syntax and R scripting. They should be stored in the R scripts folder. You can set this folder in the R settings group (available from the processing settings dialog), just like you do with the folder for regular processing scripts. Let’s have a look at a very simple script file, which calls the R method spsample to create a random grid within the boundary of the polygons in a given polygon layer. This method belongs to the maptools package. Since almost all the algorithms that you might like to incorporate into QGIS will use or generate spatial data, knowledge of spatial packages like maptools and, especially, sp, is mandatory. ##polyg=vector ##numpoints=number 10 ##output=output vector ##sp=group pts=spsample(polyg,numpoints,type="random") output=SpatialPointsDataFrame(pts, as.data.frame(pts)) 17.14. Configuring external applications 217 QGIS User Guide, Release 2.6 The first lines, which start with a double Python comment sign (##), tell QGIS the inputs of the algorithm de- scribed in the file and the outputs that it will generate. They work with exactly the same syntax as the SEXTANTE scripts that we have already seen, so they will not be described here again. When you declare an input parameter, QGIS uses that information for two things: creating the user interface to ask the user for the value of that parameter and creating a corresponding R variable that can later be used as input for R commands. In the above example, we are declaring an input of type vector named polyg. When executing the algorithm, QGIS will open in R the layer selected by the user and store it in a variable also named polyg. So, the name of a parameter is also the name of the variable that we can use in R for accesing the value of that parameter (thus, you should avoid using reserved R words as parameter names). Spatial elements such as vector and raster layers are read using the readOGR() and brick() commands (you do not have to worry about adding those commands to your description file – QGIS will do it), and they are stored as Spatial*DataFrame objects. Table fields are stored as strings containing the name of the selected field. Tables are opened using the read.csv() command. If a table entered by the user is not in CSV format, it will be converted prior to importing it into R. Additionally, raster files can be read using the readGDAL() command instead of brick() by using the ##usereadgdal. If you are an advanced user and do not want QGIS to create the object representing the layer, you can use the ##passfilename tag to indicate that you prefer a string with the filename instead. In this case, it is up to you to open the file before performing any operation on the data it contains. With the above information, we can now understand the first line of our first example script (the first line not starting with a Python comment). pts=spsample(polyg,numpoints,type="random") The variable polygon already contains a SpatialPolygonsDataFrame object, so it can be used to call the spsample method, just like the numpoints one, which indicates the number of points to add to the created sample grid. Since we have declared an output of type vector named out, we have to create a variable named out and store a Spatial*DataFrame object in it (in this case, a SpatialPointsDataFrame). You can use any name for your intermediate variables. Just make sure that the variable storing your final result has the same name that you used to declare it, and that it contains a suitable value. In this case, the result obtained from the spsample method has to be converted explicitly into a SpatialPointsDataFrame object, since it is itself an object of class ppp, which is not a suitable class to be returned to QGIS. If your algorithm generates raster layers, the way they are saved will depend on whether or not you have used the #dontuserasterpackage option. In you have used it, layers are saved using the writeGDAL() method. If not, the writeRaster() method from the raster package will be used. If you have used the #passfilename option, outputs are generated using the raster package (with writeRaster()), even though it is not used for the inputs. If your algorithm does not generate any layer, but rather a text result in the console instead, you have to indicate that you want the console to be shown once the execution is finished. To do so, just start the command lines that produce the results you want to print with the > (‘greater’) sign. The output of all other lines will not be shown. For instance, here is the description file of an algorithm that performs a normality test on a given field (column) of the attributes of a vector layer: ##layer=vector ##field=field layer ##nortest=group library(nortest) >lillie.test(layer[[field]]) The output of the last line is printed, but the output of the first is not (and neither are the outputs from other command lines added automatically by QGIS). 218 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 If your algorithm creates any kind of graphics (using the plot() method), add the following line: ##showplots This will cause QGIS to redirect all R graphical outputs to a temporary file, which will be opened once R execution has finished. Both graphics and console results will be shown in the processing results manager. For more information, please check the script files provided with SEXTANTE. Most of them are rather simple and will greatly help you understand how to create your own scripts. Note: rgdal and maptools libraries are loaded by default, so you do not have to add the corresponding library() commands (you just have to make sure that those two packages are installed in your R distribution). However, other additional libraries that you might need have to be explicitly loaded. Just add the necessary com- mands at the beginning of your script. You also have to make sure that the corresponding packages are installed in the R distribution used by QGIS. The processing framework will not take care of any package installation. If you run a script that requires a package that is not installed, the execution will fail, and SEXTANTE will try to detect which packages are missing. You must install those missing libraries manually before you can run the algorithm. GRASS Configuring GRASS is not much different from configuring SAGA. First, the path to the GRASS folder has to be defined, but only if you are running Windows. Additionaly, a shell interpreter (usually msys.exe, which can be found in most GRASS for Windows distributions) has to be defined and its path set up as well. By default, the processing framework tries to configure its GRASS connector to use the GRASS distribution that ships along with QGIS. This should work without problems in most systems, but if you experience problems, you might have to configure the GRASS connector manually. Also, if you want to use a different GRASS installation, you can change that setting and point to the folder where the other version is installed. GRASS 6.4 is needed for algorithms to work correctly. If you are running Linux, you just have to make sure that GRASS is correctly installed, and that it can be run without problem from a console. GRASS algorithms use a region for calculations. This region can be defined manually using values similar to the ones found in the SAGA configuration, or automatically, taking the minimum extent that covers all the input layers used to execute the algorithm each time. If the latter approach is the behaviour you prefer, just check the Use min covering region option in the GRASS configuration parameters. The last parameter that has to be configured is related to the mapset. A mapset is needed to run GRASS, and the processing framework creates a temporary one for each execution. You have to specify if the data you are working with uses geographical (lat/lon) coordinates or projected ones. GDAL No additional configuration is needed to run GDAL algorithms. Since they are already incorporated into QGIS, the algorithms can infer their configuration from it. Orfeo Toolbox Orfeo Toolbox (OTB) algorithms can be run from QGIS if you have OTB installed in your system and you have configured QGIS properly, so it can find all necessary files (command-line tools and libraries). As in the case of SAGA, OTB binaries are included in the stand-alone installer for Windows, but they are not included if you are runing Linux, so you have to download and install the software yourself. Please check the OTB website for more information. 17.14. Configuring external applications 219 QGIS User Guide, Release 2.6 Once OTB is installed, start QGIS, open the processing configuration dialog and configure the OTB algorithm provider. In the Orfeo Toolbox (image analysis) block, you will find all settings related to OTB. First, ensure that algorithms are enabled. Then, configure the path to the folder where OTB command-line tools and libraries are installed: • Usually OTB applications folder points to /usr/lib/otb/applications and OTB command line tools folder is /usr/bin. • If you use the OSGeo4W installer, then install otb-bin package and enter C:\OSGeo4W\apps\orfeotoolbox\applications as OTB applications folder and C:\OSGeo4W\bin as OTB command line tools folder. These values should be configured by de- fault, but if you have a different OTB installation, configure them to the corresponding values in your system. TauDEM To use this provider, you need to install TauDEM command line tools. 17.14.8 Windows Please visit the TauDEM homepage for installation instructions and precompiled binaries for 32-bit and 64-bit systems. IMPORTANT: You need TauDEM 5.0.6 executables. Version 5.2 is currently not supported. 17.14.9 Linux There are no packages for most Linux distributions, so you should compile TauDEM by yourself. As TauDEM uses MPICH2, first install it using your favorite package manager. Alternatively, TauDEM works fine with Open MPI, so you can use it instead of MPICH2. Download TauDEM 5.0.6 source code and extract the files in some folder. Open the linearpart.h file, and after line #include "mpi.h" add a new line with #include so you’ll get #include "mpi.h" #include Save the changes and close the file. Now open tiffIO.h, find line #include "stdint.h" and replace quotes ("") with <>, so you’ll get #include Save the changes and close the file. Create a build directory and cd into it mkdir build cd build Configure your build with the command CXX=mpicxx cmake -DCMAKE_INSTALL_PREFIX=/usr/local .. and then compile 220 Chapter 17. QGIS processing framework QGIS User Guide, Release 2.6 make Finally, to install TauDEM into /usr/local/bin, run sudo make install . 17.15 The QGIS Commander Processing includes a practical tool that allows you to run algorithms without having to use the toolbox, but just by typing the name of the algorithm you want to run. This tool is known as the QGIS commander, and it is just a simple text box with autocompletion where you type the command you want to run. Figure 17.29: The QGIS Commander The Commander is started from the Analysis menu or, more practically, by pressing Shift + Ctrl + M (you can change that default keyboard shortcut in the QGIS configuration if you prefer a different one). Apart from executing Processing algorithms, the Commander gives you access to most of the functionality in QGIS, which means that it gives you a practical and efficient way of running QGIS tasks and allows you to control QGIS with reduced usage of buttons and menus. Moreover, the Commander is configurable, so you can add your custom commands and have them just a few keystrokes away, making it a powerful tool to help you become more productive in your daily work with QGIS. 17.15.1 Available commands The commands available in the Commander fall in the following categories: • Processing algorithms. These are shown as Processing algorithm: . • Menu items. These are shown as Menu item: . All menus items available from the QGIS interface are available, even if they are included in a submenu. • Python functions. You can create short Python functions that will be then included in the list of available commands. They are shown as Function: . To run any of the above, just start typing and then select the corresponding element from the list of available commands that appears after filtering the whole list of commands with the text you have entered. In the case of calling a Python function, you can select the entry in the list, which is pre- fixed by Function: (for instance, Function: removeall), or just directly type the function name (‘‘removeall in the previous example). There is no need to add brackets after the func- tion name. 17.15. The QGIS Commander 221 QGIS User Guide, Release 2.6 17.15.2 Creating custom functions Custom functions are added by entering the corresponding Python code in the commands.py file that is found in the .qgis/sextante/commander directory in your user folder. It is just a simple Python file where you can add the functions that you need. The file is created with a few example functions the first time you open the Commander. If you haven’t launched the Commander yet, you can create the file yourself. To edit the commands file, use your favorite text editor. You can also use a built-in editor by calling the edit command from the Commander. It will open the editor with the commands file, and you can edit it directly and then save your changes. For instance, you can add the following function, which removes all layers: from qgis.gui import * def removeall(): mapreg= QgsMapLayerRegistry.instance() mapreg.removeAllMapLayers() Once you have added the function, it will be available in the Commander, and you can invoke it by typing removeall. There is no need to do anything apart from writing the function itself. Functions can receive parameters. Add *args to your function definition to receive arguments. When calling the function from the Commander, parameters have to be passed separated by spaces. Here is an example of a function that loads a layer and takes a parameter with the filename of the layer to load. import processing def load(*args): processing.load(args[0]) If you want to load the layer in /home/myuser/points.shp, type load /home/myuser/points.shp in the Commander text box. . 222 Chapter 17. QGIS processing framework CHAPTER 18 Processing providers and algorithms . 18.1 GDAL algorithm provider GDAL (Geospatial Data Abstraction Library) is a translator library for raster and vector geospatial data formats. . 18.1.1 GDAL analysis Aspect Description Parameters Input layer [raster] Band number [number] Default: 1 Compute edges [boolean] Default: False Use Zevenbergen&Thorne formula (instead of the Horn’s one) [boolean] Default: False Return trigonometric angle (instead of azimuth) [boolean] Default: False Return o for flat (instead of -9999) [boolean] Default: False 223 QGIS User Guide, Release 2.6 Outputs Output file [raster] Console usage processing.runalg(’gdalogr:aspect’, input, band, compute_edges, zevenbergen, trig_angle, zero_flat, output) See also Color relief Description Parameters Input layer [raster] Band number [number] Default: 1 Compute edges [boolean] Default: False Color configuration file [file] Matching mode [selection] Options: • 0 — “0,0,0,0” RGBA • 1 — Exact color • 2 — Nearest color Default: 0 Outputs Output file [raster] Console usage processing.runalg(’gdalogr:colorrelief’, input, band, compute_edges, color_table, match_mode, output) See also Fill nodata Description 224 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input layer [raster] Search distance [number] Default: 100 Smooth iterations [number] Default: 0 Band to operate on [number] Default: 1 Validity mask [raster] Optional. Do not use default validity mask [boolean] Default: False Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:fillnodata’, input, distance, iterations, band, mask, no_default_mask, output) See also Grid (Moving average) Description Parameters Input layer [vector: point] Z field [tablefield: numeric] Optional. Radius 1 [number] Default: 0.0 Radius 2 [number] Default: 0.0 Min points [number] Default: 0.0 Angle [number] Default: 0.0 18.1. GDAL algorithm provider 225 QGIS User Guide, Release 2.6 Nodata [number] Default: 0.0 Output raster type [selection] Options: • 0 — Byte • 1 — Int16 • 2 — UInt16 • 3 — UInt32 • 4 — Int32 • 5 — Float32 • 6 — Float64 • 7 — CInt16 • 8 — CInt32 • 9 — CFloat32 • 10 — CFloat64 Default: 5 Outputs Output file [raster] Console usage processing.runalg(’gdalogr:gridaverage’, input, z_field, radius_1, radius_2, min_points, angle, nodata, rtype, output) See also Grid (Data metrics) Description Parameters Input layer [vector: point] Z field [tablefield: numeric] Optional. Metrics [selection] Options: • 0 — Minimum • 1 — Maximum • 2 — Range 226 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 3 — Count • 4 — Average distance • 5 — Average distance between points Default: 0 Radius 1 [number] Default: 0.0 Radius 2 [number] Default: 0.0 Min points [number] Default: 0.0 Angle [number] Default: 0.0 Nodata [number] Default: 0.0 Output raster type [selection] Options: • 0 — Byte • 1 — Int16 • 2 — UInt16 • 3 — UInt32 • 4 — Int32 • 5 — Float32 • 6 — Float64 • 7 — CInt16 • 8 — CInt32 • 9 — CFloat32 • 10 — CFloat64 Default: 5 Outputs Output file [raster] Console usage processing.runalg(’gdalogr:griddatametrics’, input, z_field, metric, radius_1, radius_2, min_points, angle, nodata, rtype, output) 18.1. GDAL algorithm provider 227 QGIS User Guide, Release 2.6 See also Grid (Inverse distance to a power) Description Parameters Input layer [vector: point] Z field [tablefield: numeric] Optional. Power [number] Default: 2.0 Smothing [number] Default: 0.0 Radius 1 [number] Default: 0.0 Radius 2 [number] Default: 0.0 Max points [number] Default: 0.0 Min points [number] Default: 0.0 Angle [number] Default: 0.0 Nodata [number] Default: 0.0 Output raster type [selection] Options: • 0 — Byte • 1 — Int16 • 2 — UInt16 • 3 — UInt32 • 4 — Int32 • 5 — Float32 • 6 — Float64 • 7 — CInt16 • 8 — CInt32 • 9 — CFloat32 228 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 10 — CFloat64 Default: 5 Outputs Output file [raster] Console usage processing.runalg(’gdalogr:gridinvdist’, input, z_field, power, smothing, radius_1, radius_2, max_points, min_points, angle, nodata, rtype, output) See also Grid (Nearest neighbor) Description Parameters Input layer [vector: point] Z field [tablefield: numeric] Optional. Radius 1 [number] Default: 0.0 Radius 2 [number] Default: 0.0 Angle [number] Default: 0.0 Nodata [number] Default: 0.0 Output raster type [selection] Options: • 0 — Byte • 1 — Int16 • 2 — UInt16 • 3 — UInt32 • 4 — Int32 • 5 — Float32 • 6 — Float64 • 7 — CInt16 • 8 — CInt32 18.1. GDAL algorithm provider 229 QGIS User Guide, Release 2.6 • 9 — CFloat32 • 10 — CFloat64 Default: 5 Outputs Output file [raster] Console usage processing.runalg(’gdalogr:gridnearestneighbor’, input, z_field, radius_1, radius_2, angle, nodata, rtype, output) See also Hillshade Description Parameters Input layer [raster] Band number [number] Default: 1 Compute edges [boolean] Default: False Use Zevenbergen&Thorne formula (instead of the Horn’s one) [boolean] Default: False Z factor (vertical exaggeration) [number] Default: 1.0 Scale (ratio of vert. units to horiz.) [number] Default: 1.0 Azimuth of the light [number] Default: 315.0 Altitude of the light [number] Default: 45.0 Outputs Output file [raster] 230 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’gdalogr:hillshade’, input, band, compute_edges, zevenbergen, z_factor, scale, azimuth, altitude, output) See also Near black Description Parameters Input layer [raster] How far from black (white) [number] Default: 15 Search for nearly white pixels instead of nearly black [boolean] Default: False Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:nearblack’, input, near, white, output) See also Proximity (raster distance) Description Parameters Input layer [raster] Values [string] Default: (not set) Dist units [selection] Options: • 0 — GEO • 1 — PIXEL 18.1. GDAL algorithm provider 231 QGIS User Guide, Release 2.6 Default: 0 Max dist (negative value to ignore) [number] Default: -1 No data (negative value to ignore) [number] Default: -1 Fixed buf val (negative value to ignore) [number] Default: -1 Output raster type [selection] Options: • 0 — Byte • 1 — Int16 • 2 — UInt16 • 3 — UInt32 • 4 — Int32 • 5 — Float32 • 6 — Float64 • 7 — CInt16 • 8 — CInt32 • 9 — CFloat32 • 10 — CFloat64 Default: 5 Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:proximity’, input, values, units, max_dist, nodata, buf_val, rtype, output) See also Roughness Description Parameters Input layer [raster] Band number [number] Default: 1 232 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Compute edges [boolean] Default: False Outputs Output file [raster] Console usage processing.runalg(’gdalogr:roughness’, input, band, compute_edges, output) See also Sieve Description Parameters Input layer [raster] Threshold [number] Default: 2 Pixel connection [selection] Options: •0—4 •1—8 Default: 0 Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:sieve’, input, threshold, connections, output) See also Slope Description 18.1. GDAL algorithm provider 233 QGIS User Guide, Release 2.6 Parameters Input layer [raster] Band number [number] Default: 1 Compute edges [boolean] Default: False Use Zevenbergen&Thorne formula (instead of the Horn’s one) [boolean] Default: False Slope expressed as percent (instead of degrees) [boolean] Default: False Scale (ratio of vert. units to horiz.) [number] Default: 1.0 Outputs Output file [raster] Console usage processing.runalg(’gdalogr:slope’, input, band, compute_edges, zevenbergen, as_percent, scale, output) See also TPI (Topographic Position Index) Description Parameters Input layer [raster] Band number [number] Default: 1 Compute edges [boolean] Default: False Outputs Output file [raster] 234 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’gdalogr:tpitopographicpositionindex’, input, band, compute_edges, output) See also TRI (Terrain Ruggedness Index) Description Parameters Input layer [raster] Band number [number] Default: 1 Compute edges [boolean] Default: False Outputs Output file [raster] Console usage processing.runalg(’gdalogr:triterrainruggednessindex’, input, band, compute_edges, output) See also . 18.1.2 GDAL conversion gdal2xyz Description Parameters Input layer [raster] Band number [number] Default: 1 18.1. GDAL algorithm provider 235 QGIS User Guide, Release 2.6 Outputs Output file [table] Console usage processing.runalg(’gdalogr:gdal2xyz’, input, band, output) See also PCT to RGB Description Parameters Input layer [raster] Band to convert [selection] Options: •0—1 •1—2 •2—3 •3—4 •4—5 •5—6 •6—7 •7—8 •8—9 • 9 — 10 • 10 — 11 • 11 — 12 • 12 — 13 • 13 — 14 • 14 — 15 • 15 — 16 • 16 — 17 • 17 — 18 • 18 — 19 • 19 — 20 • 20 — 21 236 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 21 — 22 • 22 — 23 • 23 — 24 • 24 — 25 Default: 0 Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:pcttorgb’, input, nband, output) See also Polygonize (raster to vector) Description Parameters Input layer [raster] Output field name [string] Default: DN Outputs Output layer [vector] Console usage processing.runalg(’gdalogr:polygonize’, input, field, output) See also Rasterize (vector to raster) Description 18.1. GDAL algorithm provider 237 QGIS User Guide, Release 2.6 Parameters Input layer [vector: any] Attribute field [tablefield: any] Write values inside an existing raster layer(*)[boolean] Default: False Set output raster size (ignored if above option is checked) [selection] Options: • 0 — Output size in pixels • 1 — Output resolution in map units per pixel Default: 1 Horizontal [number] Default: 100.0 Vertical [number] Default: 100.0 Raster type [selection] Options: • 0 — Byte • 1 — Int16 • 2 — UInt16 • 3 — UInt32 • 4 — Int32 • 5 — Float32 • 6 — Float64 • 7 — CInt16 • 8 — CInt32 • 9 — CFloat32 • 10 — CFloat64 Default: 0 Outputs Output layer: mandatory to choose an existing raster layer if the (*) option is selected [raster] Console usage processing.runalg(’gdalogr:rasterize’, input, field, writeover, dimensions, width, height, rtype, output) 238 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also RGB to PCT Description Parameters Input layer [raster] Number of colors [number] Default: 2 Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:rgbtopct’, input, ncolors, output) See also Translate (convert format) Description Parameters Input layer [raster] Set the size of the output file (In pixels or %) [number] Default: 100 Output size is a percentage of input size [boolean] Default: True Nodata value, leave as none to take the nodata value from input [string] Default: none Expand [selection] Options: • 0 — none • 1 — gray • 2 — rgb 18.1. GDAL algorithm provider 239 QGIS User Guide, Release 2.6 • 3 — rgba Default: 0 Output projection for output file [leave blank to use input projection] [crs] Default: None Subset based on georeferenced coordinates [extent] Default: 0,1,0,1 Copy all subdatasets of this file to individual output files [boolean] Default: False Additional creation parameters [string] Optional. Default: (not set) Output raster type [selection] Options: • 0 — Byte • 1 — Int16 • 2 — UInt16 • 3 — UInt32 • 4 — Int32 • 5 — Float32 • 6 — Float64 • 7 — CInt16 • 8 — CInt32 • 9 — CFloat32 • 10 — CFloat64 Default: 5 Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:translate’, input, outsize, outsize_perc, no_data, expand, srs, projwin, sds, extra, rtype, output) See also . 240 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 18.1.3 GDAL extraction Clip raster by extent Description Parameters Input layer [raster] Nodata value, leave as none to take the nodata value from input [string] Default: none Clipping extent [extent] Default: 0,1,0,1 Additional creation parameters [string] Optional. Default: (not set) Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:cliprasterbyextent’, input, no_data, projwin, extra, output) See also Clip raster by mask layer Description Parameters Input layer [raster] Mask layer [vector: polygon] Nodata value, leave as none to take the nodata value from input [string] Default: none Create and output alpha band [boolean] Default: False 18.1. GDAL algorithm provider 241 QGIS User Guide, Release 2.6 Keep resolution of output raster [boolean] Default: False Additional creation parameters [string] Optional. Default: (not set) Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:cliprasterbymasklayer’, input, mask, no_data, alpha_band, keep_resolution, extra, output) See also Contour Description Parameters Input layer [raster] Interval between contour lines [number] Default: 10.0 Attribute name (if not set, no elevation attribute is attached) [string] Optional. Default: ELEV Additional creation parameters [string] Optional. Default: (not set) Outputs Output file for contour lines (vector) [vector] Console usage processing.runalg(’gdalogr:contour’, input_raster, interval, field_name, extra, output_vector) 242 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also . 18.1.4 GDAL miscellaneous Build Virtual Raster Description Parameters Input layers [multipleinput: rasters] Resolution [selection] Options: • 0 — average • 1 — highest • 2 — lowest Default: 0 Layer stack [boolean] Default: True Allow projection difference [boolean] Default: False Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:buildvirtualraster’, input, resolution, separate, proj_difference, output) See also Merge Description 18.1. GDAL algorithm provider 243 QGIS User Guide, Release 2.6 Parameters Input layers [multipleinput: rasters] Grab pseudocolor table from first layer [boolean] Default: False Layer stack [boolean] Default: False Output raster type [selection] Options: • 0 — Byte • 1 — Int16 • 2 — UInt16 • 3 — UInt32 • 4 — Int32 • 5 — Float32 • 6 — Float64 • 7 — CInt16 • 8 — CInt32 • 9 — CFloat32 • 10 — CFloat64 Default: 5 Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:merge’, input, pct, separate, rtype, output) See also Build overviews (pyramids) Description Parameters Input layer [raster] Overview levels [string] Default: 2 4 8 16 244 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Remove all existing overviews [boolean] Default: False Resampling method [selection] Options: • 0 — nearest • 1 — average • 2 — gauss • 3 — cubic • 4 — average_mp • 5 — average_magphase • 6 — mode Default: 0 Overview format [selection] Options: • 0 — Internal (if possible) • 1 — External (GTiff .ovr) • 2 — External (ERDAS Imagine .aux) Default: 0 Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:overviews’, input, levels, clean, resampling_method, format) See also Information Description Parameters Input layer [raster] Suppress GCP info [boolean] Default: False Suppress metadata info [boolean] Default: False 18.1. GDAL algorithm provider 245 QGIS User Guide, Release 2.6 Outputs Layer information [html] Console usage processing.runalg(’gdalorg:rasterinfo’, input, nogcp, nometadata, output) See also . 18.1.5 GDAL projections Extract projection Description Parameters Input file [raster] Create also .prj file [boolean] Default: False Outputs Console usage processing.runalg(’gdalogr:extractprojection’, input, prj_file) See also Warp (reproject) Description Parameters Input layer [raster] Source SRS (EPSG Code) [crs] Default: EPSG:4326 Destination SRS (EPSG Code) [crs] Default: EPSG:4326 246 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Output file resolution in target georeferenced units (leave 0 for no change) [number] Default: 0.0 Resampling method [selection] Options: • 0 — near • 1 — bilinear • 2 — cubic • 3 — cubicspline • 4 — lanczos Default: 0 Additional creation parameters [string] Optional. Default: (not set) Output raster type [selection] Options: • 0 — Byte • 1 — Int16 • 2 — UInt16 • 3 — UInt32 • 4 — Int32 • 5 — Float32 • 6 — Float64 • 7 — CInt16 • 8 — CInt32 • 9 — CFloat32 • 10 — CFloat64 Default: 5 Outputs Output layer [raster] Console usage processing.runalg(’gdalogr:warpreproject’, input, source_srs, dest_srs, tr, method, extra, rtype, output) See also . 18.1. GDAL algorithm provider 247 QGIS User Guide, Release 2.6 18.1.6 OGR conversion Convert format Description Parameters Input layer [vector: any] Destination Format [selection] Options: • 0 — ESRI Shapefile • 1 — GeoJSON • 2 — GeoRSS • 3 — SQLite • 4 — GMT • 5 — MapInfo File • 6 — INTERLIS 1 • 7 — INTERLIS 2 • 8 — GML • 9 — Geoconcept • 10 — DXF • 11 — DGN • 12 — CSV • 13 — BNA • 14 — S57 • 15 — KML • 16 — GPX • 17 — PGDump • 18 — GPSTrackMaker • 19 — ODS • 20 — XLSX • 21 — PDF Default: 0 Creation Options [string] Optional. Default: (not set) 248 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Output layer [vector] Console usage processing.runalg(’gdalogr:convertformat’, input_layer, format, options, output_layer) See also . 18.1.7 OGR geoprocessing Clip vectors by extent Description Parameters Input layer [vector: any] Clip extent [extent] Default: 0,1,0,1 Additional creation Options [string] Optional. Default: (not set) Outputs Output layer [vector] Console usage processing.runalg(’gdalogr:clipvectorsbyextent’, input_layer, clip_extent, options, output_layer) See also Clip vectors by polygon Description 18.1. GDAL algorithm provider 249 QGIS User Guide, Release 2.6 Parameters Input layer [vector: any] Clip layer [vector: polygon] Additional creation Options [string] Optional. Default: (not set) Outputs Output layer [vector] Console usage processing.runalg(’gdalogr:clipvectorsbypolygon’, input_layer, clip_layer, options, output_layer) See also . 18.1.8 OGR miscellaneous Execute SQL Description Parameters Input layer [vector: any] SQL [string] Default: (not set) Outputs SQL result [vector] Console usage processing.runalg(’gdalogr:executesql’, input, sql, output) 250 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Import Vector into PostGIS database (available connections) Description Parameters Database (connection name) [selection] Options: • 0 — local Default: 0 Input layer [vector: any] Output geometry type [selection] Options: •0— • 1 — NONE • 2 — GEOMETRY • 3 — POINT • 4 — LINESTRING • 5 — POLYGON • 6 — GEOMETRYCOLLECTION • 7 — MULTIPOINT • 8 — MULTIPOLYGON • 9 — MULTILINESTRING Default: 5 Input CRS (EPSG Code) [crs] Default: EPSG:4326 Output CRS (EPSG Code) [crs] Default: EPSG:4326 Schema name [string] Optional. Default: public Table name, leave blank to use input name [string] Optional. Default: (not set) Primary Key [string] Optional. Default: id 18.1. GDAL algorithm provider 251 QGIS User Guide, Release 2.6 Geometry column name [string] Optional. Default: geom Vector dimensions [selection] Options: •0—2 •1—3 Default: 0 Distance tolerance for simplification [string] Optional. Default: (not set) Maximum distance between 2 nodes (densification) [string] Optional. Default: (not set) Select features by extent (defined in input layer CRS) [extent] Default: 0,1,0,1 Clip the input layer using the above (rectangle) extent [boolean] Default: False Select features using a SQL "WHERE" statement (Ex: column="value") [string] Optional. Default: (not set) Group "n" features per transaction (Default: 20000) [string] Optional. Default: (not set) Overwrite existing table? [boolean] Default: True Append to existing table? [boolean] Default: False Append and add new fields to existing table? [boolean] Default: False Do not launder columns/table name/s? [boolean] Default: False Do not create Spatial Index? [boolean] Default: False Continue after a failure, skipping the failed feature [boolean] Default: False 252 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Additional creation options [string] Optional. Default: (not set) Outputs Console usage processing.runalg(’gdalogr:importvectorintopostgisdatabaseavailableconnections’, database, input_layer, gtype, s_srs, t_srs, schema, table, pk, geocolumn, dim, simplify, segmentize, spat, clip, where, gt, overwrite, append, addfields, launder, index, skipfailures, options) See also Import Vector into PostGIS database (new connection) Description Parameters Input layer [vector: any] Output geometry type [selection] Options: •0— • 1 — NONE • 2 — GEOMETRY • 3 — POINT • 4 — LINESTRING • 5 — POLYGON • 6 — GEOMETRYCOLLECTION • 7 — MULTIPOINT • 8 — MULTIPOLYGON • 9 — MULTILINESTRING Default: 5 Input CRS (EPSG Code) [crs] Default: EPSG:4326 Output CRS (EPSG Code) [crs] Default: EPSG:4326 Host [string] Default: localhost Port [string] Default: 5432 18.1. GDAL algorithm provider 253 QGIS User Guide, Release 2.6 Username [string] Default: (not set) Database Name [string] Default: (not set) Password [string] Default: (not set) Schema name [string] Optional. Default: public Table name, leave blank to use input name [string] Optional. Default: (not set) Primary Key [string] Optional. Default: id Geometry column name [string] Optional. Default: geom Vector dimensions [selection] Options: •0—2 •1—3 Default: 0 Distance tolerance for simplification [string] Optional. Default: (not set) Maximum distance between 2 nodes (densification) [string] Optional. Default: (not set) Select features by extent (defined in input layer CRS) [extent] Default: 0,1,0,1 Clip the input layer using the above (rectangle) extent [boolean] Default: False Select features using a SQL "WHERE" statement (Ex: column="value") [string] Optional. Default: (not set) 254 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Group "n" features per transaction (Default: 20000) [string] Optional. Default: (not set) Overwrite existing table? [boolean] Default: True Append to existing table? [boolean] Default: False Append and add new fields to existing table? [boolean] Default: False Do not launder columns/table name/s? [boolean] Default: False Do not create Spatial Index? [boolean] Default: False Continue after a failure, skipping the failed feature [boolean] Default: False Additional creation options [string] Optional. Default: (not set) Outputs Console usage processing.runalg(’gdalogr:importvectorintopostgisdatabasenewconnection’, input_layer, gtype, s_srs, t_srs, host, port, user, dbname, password, schema, table, pk, geocolumn, dim, simplify, segmentize, spat, clip, where, gt, overwrite, append, addfields, launder, index, skipfailures, options) See also Information Description Parameters Input layer [vector: any] Outputs Layer information [html] 18.1. GDAL algorithm provider 255 QGIS User Guide, Release 2.6 Console usage processing.runalg(’gdalogr:information’, input, output) See also . 18.2 LAStools LAStools is a collection of highly efficient, multicore command line tools for LiDAR data processing. 18.2.1 las2las_filter Description Parameters verbose [boolean] Default: False input LAS/LAZ file [file] Optional. filter (by return, classification, flags) [selection] Options: •0—— • 1 — keep_last • 2 — keep_first • 3 — keep_middle • 4 — keep_single • 5 — drop_single • 6 — keep_double • 7 — keep_class 2 • 8 — keep_class 2 8 • 9 — keep_class 8 • 10 — keep_class 6 • 11 — keep_class 9 • 12 — keep_class 3 4 5 • 13 — keep_class 2 6 • 14 — drop_class 7 • 15 — drop_withheld 256 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Default: 0 second filter (by return, classification, flags) [selection] Options: •0—— • 1 — keep_last • 2 — keep_first • 3 — keep_middle • 4 — keep_single • 5 — drop_single • 6 — keep_double • 7 — keep_class 2 • 8 — keep_class 2 8 • 9 — keep_class 8 • 10 — keep_class 6 • 11 — keep_class 9 • 12 — keep_class 3 4 5 • 13 — keep_class 2 6 • 14 — drop_class 7 • 15 — drop_withheld Default: 0 filter (by coordinate, intensity, GPS time, ...) [selection] Options: •0—— • 1 — clip_x_above • 2 — clip_x_below • 3 — clip_y_above • 4 — clip_y_below • 5 — clip_z_above • 6 — clip_z_below • 7 — drop_intensity_above • 8 — drop_intensity_below • 9 — drop_gps_time_above • 10 — drop_gps_time_below • 11 — drop_scan_angle_above • 12 — drop_scan_angle_below • 13 — keep_point_source • 14 — drop_point_source • 15 — drop_point_source_above 18.2. LAStools 257 QGIS User Guide, Release 2.6 • 16 — drop_point_source_below • 17 — keep_user_data • 18 — drop_user_data • 19 — drop_user_data_above • 20 — drop_user_data_below • 21 — keep_every_nth • 22 — keep_random_fraction • 23 — thin_with_grid Default: 0 value for filter (by coordinate, intensity, GPS time, ...) [string] Default: (not set) second filter (by coordinate, intensity, GPS time, ...) [selection] Options: •0—— • 1 — clip_x_above • 2 — clip_x_below • 3 — clip_y_above • 4 — clip_y_below • 5 — clip_z_above • 6 — clip_z_below • 7 — drop_intensity_above • 8 — drop_intensity_below • 9 — drop_gps_time_above • 10 — drop_gps_time_below • 11 — drop_scan_angle_above • 12 — drop_scan_angle_below • 13 — keep_point_source • 14 — drop_point_source • 15 — drop_point_source_above • 16 — drop_point_source_below • 17 — keep_user_data • 18 — drop_user_data • 19 — drop_user_data_above • 20 — drop_user_data_below • 21 — keep_every_nth • 22 — keep_random_fraction • 23 — thin_with_grid Default: 0 258 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 value for second filter (by coordinate, intensity, GPS time, ...) [string] Default: (not set) Outputs output LAS/LAZ file [file] Console usage processing.runalg(’lidartools:las2lasfilter’, verbose, input_laslaz, filter_return_class_flags1, filter_return_class_flags2, filter_coords_intensity1, filter_coords_intensity1_arg, filter_coords_intensity2, filter_coords_intensity2_arg, output_laslaz) See also 18.2.2 las2las_project Description Parameters verbose [boolean] Default: False input LAS/LAZ file [file] Optional. source projection [selection] Options: •0—— • 1 — utm • 2 — sp83 • 3 — sp27 • 4 — longlat • 5 — latlong Default: 0 source utm zone [selection] Options: •0—— • 1 — 1 (north) • 2 — 2 (north) • 3 — 3 (north) • 4 — 4 (north) • 5 — 5 (north) • 6 — 6 (north) 18.2. LAStools 259 QGIS User Guide, Release 2.6 • 7 — 7 (north) • 8 — 8 (north) • 9 — 9 (north) • 10 — 10 (north) • 11 — 11 (north) • 12 — 12 (north) • 13 — 13 (north) • 14 — 14 (north) • 15 — 15 (north) • 16 — 16 (north) • 17 — 17 (north) • 18 — 18 (north) • 19 — 19 (north) • 20 — 20 (north) • 21 — 21 (north) • 22 — 22 (north) • 23 — 23 (north) • 24 — 24 (north) • 25 — 25 (north) • 26 — 26 (north) • 27 — 27 (north) • 28 — 28 (north) • 29 — 29 (north) • 30 — 30 (north) • 31 — 31 (north) • 32 — 32 (north) • 33 — 33 (north) • 34 — 34 (north) • 35 — 35 (north) • 36 — 36 (north) • 37 — 37 (north) • 38 — 38 (north) • 39 — 39 (north) • 40 — 40 (north) • 41 — 41 (north) • 42 — 42 (north) • 43 — 43 (north) • 44 — 44 (north) • 45 — 45 (north) 260 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 46 — 46 (north) • 47 — 47 (north) • 48 — 48 (north) • 49 — 49 (north) • 50 — 50 (north) • 51 — 51 (north) • 52 — 52 (north) • 53 — 53 (north) • 54 — 54 (north) • 55 — 55 (north) • 56 — 56 (north) • 57 — 57 (north) • 58 — 58 (north) • 59 — 59 (north) • 60 — 60 (north) • 61 — 1 (south) • 62 — 2 (south) • 63 — 3 (south) • 64 — 4 (south) • 65 — 5 (south) • 66 — 6 (south) • 67 — 7 (south) • 68 — 8 (south) • 69 — 9 (south) • 70 — 10 (south) • 71 — 11 (south) • 72 — 12 (south) • 73 — 13 (south) • 74 — 14 (south) • 75 — 15 (south) • 76 — 16 (south) • 77 — 17 (south) • 78 — 18 (south) • 79 — 19 (south) • 80 — 20 (south) • 81 — 21 (south) • 82 — 22 (south) • 83 — 23 (south) • 84 — 24 (south) 18.2. LAStools 261 QGIS User Guide, Release 2.6 • 85 — 25 (south) • 86 — 26 (south) • 87 — 27 (south) • 88 — 28 (south) • 89 — 29 (south) • 90 — 30 (south) • 91 — 31 (south) • 92 — 32 (south) • 93 — 33 (south) • 94 — 34 (south) • 95 — 35 (south) • 96 — 36 (south) • 97 — 37 (south) • 98 — 38 (south) • 99 — 39 (south) • 100 — 40 (south) • 101 — 41 (south) • 102 — 42 (south) • 103 — 43 (south) • 104 — 44 (south) • 105 — 45 (south) • 106 — 46 (south) • 107 — 47 (south) • 108 — 48 (south) • 109 — 49 (south) • 110 — 50 (south) • 111 — 51 (south) • 112 — 52 (south) • 113 — 53 (south) • 114 — 54 (south) • 115 — 55 (south) • 116 — 56 (south) • 117 — 57 (south) • 118 — 58 (south) • 119 — 59 (south) • 120 — 60 (south) Default: 0 source state plane code [selection] Options: 262 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 •0—— • 1 — AK_10 • 2 — AK_2 • 3 — AK_3 • 4 — AK_4 • 5 — AK_5 • 6 — AK_6 • 7 — AK_7 • 8 — AK_8 • 9 — AK_9 • 10 — AL_E • 11 — AL_W • 12 — AR_N • 13 — AR_S • 14 — AZ_C • 15 — AZ_E • 16 — AZ_W • 17 — CA_I • 18 — CA_II • 19 — CA_III • 20 — CA_IV • 21 — CA_V • 22 — CA_VI • 23 — CA_VII • 24 — CO_C • 25 — CO_N • 26 — CO_S • 27 — CT • 28 — DE • 29 — FL_E • 30 — FL_N • 31 — FL_W • 32 — GA_E • 33 — GA_W • 34 — HI_1 • 35 — HI_2 • 36 — HI_3 • 37 — HI_4 • 38 — HI_5 18.2. LAStools 263 QGIS User Guide, Release 2.6 • 39 — IA_N • 40 — IA_S • 41 — ID_C • 42 — ID_E • 43 — ID_W • 44 — IL_E • 45 — IL_W • 46 — IN_E • 47 — IN_W • 48 — KS_N • 49 — KS_S • 50 — KY_N • 51 — KY_S • 52 — LA_N • 53 — LA_S • 54 — MA_I • 55 — MA_M • 56 — MD • 57 — ME_E • 58 — ME_W • 59 — MI_C • 60 — MI_N • 61 — MI_S • 62 — MN_C • 63 — MN_N • 64 — MN_S • 65 — MO_C • 66 — MO_E • 67 — MO_W • 68 — MS_E • 69 — MS_W • 70 — MT_C • 71 — MT_N • 72 — MT_S • 73 — NC • 74 — ND_N • 75 — ND_S • 76 — NE_N • 77 — NE_S 264 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 78 — NH • 79 — NJ • 80 — NM_C • 81 — NM_E • 82 — NM_W • 83 — NV_C • 84 — NV_E • 85 — NV_W • 86 — NY_C • 87 — NY_E • 88 — NY_LI • 89 — NY_W • 90 — OH_N • 91 — OH_S • 92 — OK_N • 93 — OK_S • 94 — OR_N • 95 — OR_S • 96 — PA_N • 97 — PA_S • 98 — PR • 99 — RI • 100 — SC_N • 101 — SC_S • 102 — SD_N • 103 — SD_S • 104 — St.Croix • 105 — TN • 106 — TX_C • 107 — TX_N • 108 — TX_NC • 109 — TX_S • 110 — TX_SC • 111 — UT_C • 112 — UT_N • 113 — UT_S • 114 — VA_N • 115 — VA_S • 116 — VT 18.2. LAStools 265 QGIS User Guide, Release 2.6 • 117 — WA_N • 118 — WA_S • 119 — WI_C • 120 — WI_N • 121 — WI_S • 122 — WV_N • 123 — WV_S • 124 — WY_E • 125 — WY_EC • 126 — WY_W • 127 — WY_WC Default: 0 target projection [selection] Options: •0—— • 1 — utm • 2 — sp83 • 3 — sp27 • 4 — longlat • 5 — latlong Default: 0 target utm zone [selection] Options: •0—— • 1 — 1 (north) • 2 — 2 (north) • 3 — 3 (north) • 4 — 4 (north) • 5 — 5 (north) • 6 — 6 (north) • 7 — 7 (north) • 8 — 8 (north) • 9 — 9 (north) • 10 — 10 (north) • 11 — 11 (north) • 12 — 12 (north) • 13 — 13 (north) • 14 — 14 (north) • 15 — 15 (north) 266 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 16 — 16 (north) • 17 — 17 (north) • 18 — 18 (north) • 19 — 19 (north) • 20 — 20 (north) • 21 — 21 (north) • 22 — 22 (north) • 23 — 23 (north) • 24 — 24 (north) • 25 — 25 (north) • 26 — 26 (north) • 27 — 27 (north) • 28 — 28 (north) • 29 — 29 (north) • 30 — 30 (north) • 31 — 31 (north) • 32 — 32 (north) • 33 — 33 (north) • 34 — 34 (north) • 35 — 35 (north) • 36 — 36 (north) • 37 — 37 (north) • 38 — 38 (north) • 39 — 39 (north) • 40 — 40 (north) • 41 — 41 (north) • 42 — 42 (north) • 43 — 43 (north) • 44 — 44 (north) • 45 — 45 (north) • 46 — 46 (north) • 47 — 47 (north) • 48 — 48 (north) • 49 — 49 (north) • 50 — 50 (north) • 51 — 51 (north) • 52 — 52 (north) • 53 — 53 (north) • 54 — 54 (north) 18.2. LAStools 267 QGIS User Guide, Release 2.6 • 55 — 55 (north) • 56 — 56 (north) • 57 — 57 (north) • 58 — 58 (north) • 59 — 59 (north) • 60 — 60 (north) • 61 — 1 (south) • 62 — 2 (south) • 63 — 3 (south) • 64 — 4 (south) • 65 — 5 (south) • 66 — 6 (south) • 67 — 7 (south) • 68 — 8 (south) • 69 — 9 (south) • 70 — 10 (south) • 71 — 11 (south) • 72 — 12 (south) • 73 — 13 (south) • 74 — 14 (south) • 75 — 15 (south) • 76 — 16 (south) • 77 — 17 (south) • 78 — 18 (south) • 79 — 19 (south) • 80 — 20 (south) • 81 — 21 (south) • 82 — 22 (south) • 83 — 23 (south) • 84 — 24 (south) • 85 — 25 (south) • 86 — 26 (south) • 87 — 27 (south) • 88 — 28 (south) • 89 — 29 (south) • 90 — 30 (south) • 91 — 31 (south) • 92 — 32 (south) • 93 — 33 (south) 268 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 94 — 34 (south) • 95 — 35 (south) • 96 — 36 (south) • 97 — 37 (south) • 98 — 38 (south) • 99 — 39 (south) • 100 — 40 (south) • 101 — 41 (south) • 102 — 42 (south) • 103 — 43 (south) • 104 — 44 (south) • 105 — 45 (south) • 106 — 46 (south) • 107 — 47 (south) • 108 — 48 (south) • 109 — 49 (south) • 110 — 50 (south) • 111 — 51 (south) • 112 — 52 (south) • 113 — 53 (south) • 114 — 54 (south) • 115 — 55 (south) • 116 — 56 (south) • 117 — 57 (south) • 118 — 58 (south) • 119 — 59 (south) • 120 — 60 (south) Default: 0 target state plane code [selection] Options: •0—— • 1 — AK_10 • 2 — AK_2 • 3 — AK_3 • 4 — AK_4 • 5 — AK_5 • 6 — AK_6 • 7 — AK_7 • 8 — AK_8 18.2. LAStools 269 QGIS User Guide, Release 2.6 • 9 — AK_9 • 10 — AL_E • 11 — AL_W • 12 — AR_N • 13 — AR_S • 14 — AZ_C • 15 — AZ_E • 16 — AZ_W • 17 — CA_I • 18 — CA_II • 19 — CA_III • 20 — CA_IV • 21 — CA_V • 22 — CA_VI • 23 — CA_VII • 24 — CO_C • 25 — CO_N • 26 — CO_S • 27 — CT • 28 — DE • 29 — FL_E • 30 — FL_N • 31 — FL_W • 32 — GA_E • 33 — GA_W • 34 — HI_1 • 35 — HI_2 • 36 — HI_3 • 37 — HI_4 • 38 — HI_5 • 39 — IA_N • 40 — IA_S • 41 — ID_C • 42 — ID_E • 43 — ID_W • 44 — IL_E • 45 — IL_W • 46 — IN_E • 47 — IN_W 270 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 48 — KS_N • 49 — KS_S • 50 — KY_N • 51 — KY_S • 52 — LA_N • 53 — LA_S • 54 — MA_I • 55 — MA_M • 56 — MD • 57 — ME_E • 58 — ME_W • 59 — MI_C • 60 — MI_N • 61 — MI_S • 62 — MN_C • 63 — MN_N • 64 — MN_S • 65 — MO_C • 66 — MO_E • 67 — MO_W • 68 — MS_E • 69 — MS_W • 70 — MT_C • 71 — MT_N • 72 — MT_S • 73 — NC • 74 — ND_N • 75 — ND_S • 76 — NE_N • 77 — NE_S • 78 — NH • 79 — NJ • 80 — NM_C • 81 — NM_E • 82 — NM_W • 83 — NV_C • 84 — NV_E • 85 — NV_W • 86 — NY_C 18.2. LAStools 271 QGIS User Guide, Release 2.6 • 87 — NY_E • 88 — NY_LI • 89 — NY_W • 90 — OH_N • 91 — OH_S • 92 — OK_N • 93 — OK_S • 94 — OR_N • 95 — OR_S • 96 — PA_N • 97 — PA_S • 98 — PR • 99 — RI • 100 — SC_N • 101 — SC_S • 102 — SD_N • 103 — SD_S • 104 — St.Croix • 105 — TN • 106 — TX_C • 107 — TX_N • 108 — TX_NC • 109 — TX_S • 110 — TX_SC • 111 — UT_C • 112 — UT_N • 113 — UT_S • 114 — VA_N • 115 — VA_S • 116 — VT • 117 — WA_N • 118 — WA_S • 119 — WI_C • 120 — WI_N • 121 — WI_S • 122 — WV_N • 123 — WV_S • 124 — WY_E • 125 — WY_EC 272 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 126 — WY_W • 127 — WY_WC Default: 0 Outputs output LAS/LAZ file [file] Console usage processing.runalg(’lidartools:las2lasproject’, verbose, input_laslaz, source_projection, source_utm, source_sp, target_projection, target_utm, target_sp, output_laslaz) See also 18.2.3 las2las_transform Description Parameters verbose [boolean] Default: False input LAS/LAZ file [file] Optional. transform (coordinates) [selection] Options: •0—— • 1 — translate_x • 2 — translate_y • 3 — translate_z • 4 — scale_x • 5 — scale_y • 6 — scale_z • 7 — clamp_z_above • 8 — clamp_z_below Default: 0 value for transform (coordinates) [string] Default: (not set) second transform (coordinates) [selection] Options: •0—— 18.2. LAStools 273 QGIS User Guide, Release 2.6 • 1 — translate_x • 2 — translate_y • 3 — translate_z • 4 — scale_x • 5 — scale_y • 6 — scale_z • 7 — clamp_z_above • 8 — clamp_z_below Default: 0 value for second transform (coordinates) [string] Default: (not set) transform (intensities, scan angles, GPS times, ...) [selection] Options: •0—— • 1 — scale_intensity • 2 — translate_intensity • 3 — clamp_intensity_above • 4 — clamp_intensity_below • 5 — scale_scan_angle • 6 — translate_scan_angle • 7 — translate_gps_time • 8 — set_classification • 9 — set_user_data • 10 — set_point_source • 11 — scale_rgb_up • 12 — scale_rgb_down • 13 — repair_zero_returns Default: 0 value for transform (intensities, scan angles, GPS times, ...) [string] Default: (not set) second transform (intensities, scan angles, GPS times, ...) [selection] Options: •0—— • 1 — scale_intensity • 2 — translate_intensity • 3 — clamp_intensity_above • 4 — clamp_intensity_below 274 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 5 — scale_scan_angle • 6 — translate_scan_angle • 7 — translate_gps_time • 8 — set_classification • 9 — set_user_data • 10 — set_point_source • 11 — scale_rgb_up • 12 — scale_rgb_down • 13 — repair_zero_returns Default: 0 value for second transform (intensities, scan angles, GPS times, ...) [string] Default: (not set) operations (first 7 need an argument) [selection] Options: •0—— • 1 — set_point_type • 2 — set_point_size • 3 — set_version_minor • 4 — set_version_major • 5 — start_at_point • 6 — stop_at_point • 7 — remove_vlr • 8 — auto_reoffset • 9 — week_to_adjusted • 10 — adjusted_to_week • 11 — scale_rgb_up • 12 — scale_rgb_down • 13 — remove_all_vlrs • 14 — remove_extra • 15 — clip_to_bounding_box Default: 0 argument for operation [string] Default: (not set) Outputs output LAS/LAZ file [file] 18.2. LAStools 275 QGIS User Guide, Release 2.6 Console usage processing.runalg(’lidartools:las2lastransform’, verbose, input_laslaz, transform_coordinate1, transform_coordinate1_arg, transform_coordinate2, transform_coordinate2_arg, transform_other1, transform_other1_arg, transform_other2, transform_other2_arg, operation, operationarg, output_laslaz) See also 18.2.4 las2txt Description Parameters verbose [boolean] Default: False input LAS/LAZ file [file] Optional. parse_string [string] Default: xyz Outputs Output ASCII file [file] Console usage processing.runalg(’lidartools:las2txt’, verbose, input_laslaz, parse_string, output) See also 18.2.5 lasindex Description Parameters verbose [boolean] Default: False input LAS/LAZ file [file] Optional. is mobile or terrestrial LiDAR (not airborne) [boolean] Default: False 276 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Console usage processing.runalg(’lidartools:lasindex’, verbose, input_laslaz, mobile_or_terrestrial) See also 18.2.6 lasinfo Description Parameters verbose [boolean] Default: False input LAS/LAZ file [file] Optional. Outputs Output ASCII file [file] Console usage processing.runalg(’lidartools:lasinfo’, verbose, input_laslaz, output) See also 18.2.7 lasmerge Description Parameters verbose [boolean] Default: False files are flightlines [boolean] Default: True input LAS/LAZ file [file] Optional. 2nd file [file] Optional. 18.2. LAStools 277 QGIS User Guide, Release 2.6 3rd file [file] Optional. 4th file [file] Optional. 5th file [file] Optional. 6th file [file] Optional. 7th file [file] Optional. Outputs output LAS/LAZ file [file] Console usage processing.runalg(’lidartools:lasmerge’, verbose, files_are_flightlines, input_laslaz, file2, file3, file4, file5, file6, file7, output_laslaz) See also 18.2.8 lasprecision Description Parameters verbose [boolean] Default: False input LAS/LAZ file [file] Optional. Outputs Output ASCII file [file] Console usage processing.runalg(’lidartools:lasprecision’, verbose, input_laslaz, output) 278 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also 18.2.9 lasquery Description Parameters verbose [boolean] Default: False area of interest [extent] Default: 0,1,0,1 Outputs Console usage processing.runalg(’lidartools:lasquery’, verbose, aoi) See also 18.2.10 lasvalidate Description Parameters verbose [boolean] Default: False input LAS/LAZ file [file] Optional. Outputs Output XML file [file] Console usage processing.runalg(’lidartools:lasvalidate’, verbose, input_laslaz, output) 18.2. LAStools 279 QGIS User Guide, Release 2.6 See also 18.2.11 laszip Description Parameters verbose [boolean] Default: False input LAS/LAZ file [file] Optional. only report size [boolean] Default: False Outputs output LAS/LAZ file [file] Console usage processing.runalg(’lidartools:laszip’, verbose, input_laslaz, report_size, output_laslaz) See also 18.2.12 txt2las Description Parameters verbose [boolean] Default: False Input ASCII file [file] Optional. parse lines as [string] Default: xyz skip the first n lines [number] Default: 0 resolution of x and y coordinate [number] Default: 0.01 280 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 resolution of z coordinate [number] Default: 0.01 Outputs output LAS/LAZ file [file] Console usage processing.runalg(’lidartools:txt2las’, verbose, input, parse_string, skip, scale_factor_xy, scale_factor_z, output_laslaz) See also . 18.3 Modeler Tools 18.3.1 Calculator Description Parameters Formula [string] Default: (not set) dummy [number] Default: 0.0 dummy [number] Default: 0.0 dummy [number] Default: 0.0 dummy [number] Default: 0.0 dummy [number] Default: 0.0 dummy [number] Default: 0.0 dummy [number] Default: 0.0 dummy [number] Default: 0.0 18.3. Modeler Tools 281 QGIS User Guide, Release 2.6 dummy [number] Default: 0.0 dummy [number] Default: 0.0 Outputs Result [number] Console usage processing.runalg(’modelertools:calculator’, formula, number0, number1, number2, number3, number4, number5, number6, number7, number8, number9) See also 18.3.2 Raster layer bounds Description Parameters Layer [raster] Outputs min X [number] max X [number] min Y [number] max Y [number] Extent [extent] Console usage processing.runalg(’modelertools:rasterlayerbounds’, layer) See also 18.3.3 Vector layer bounds Description Parameters Layer [vector: any] 282 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs min X [number] max X [number] min Y [number] max Y [number] Extent [extent] Console usage processing.runalg(’modelertools:vectorlayerbounds’, layer) See also . 18.4 OrfeoToolbox algorithm provider Orfeo ToolBox (OTB) is an open source library of image processing algorithms. OTB is based on the medical image processing library ITK and offers particular functionalities for remote sensing image processing in gen- eral and for high spatial resolution images in particular. Targeted algorithms for high resolution optical images (Pleiades, SPOT, QuickBird, WorldView, Landsat, Ikonos), hyperspectral sensors (Hyperion) or SAR (TerraSarX, ERS, Palsar) are available. Note: Please remember that Processing contains only the interface description, so you need to install OTB by yourself and configure Processing properly. . 18.4.1 Calibration Optical calibration Description Parameters Input [raster] Available RAM (Mb) [number] Default: 128 Calibration Level [selection] Options: • 0 — toa Default: 0 18.4. OrfeoToolbox algorithm provider 283 QGIS User Guide, Release 2.6 Convert to milli reflectance [boolean] Default: True Clamp of reflectivity values between [0, 100] [boolean] Default: True Relative Spectral Response File [file] Optional. Outputs Output [raster] Console usage processing.runalg(’otb:opticalcalibration’, -in, -ram, -level, -milli, -clamp, -rsr, -out) See also . 18.4.2 Feature extrcation BinaryMorphologicalOperation (closing) Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Structuring Element Type [selection] Options: • 0 — ball Default: 0 The Structuring Element Radius [number] Default: 5 Morphological Operation [selection] Options: • 0 — closing Default: 0 284 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:binarymorphologicaloperationclosing’, -in, -channel, -ram, -structype, -structype.ball.xradius, -filter, -out) See also BinaryMorphologicalOperation (dilate) Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Structuring Element Type [selection] Options: • 0 — ball Default: 0 The Structuring Element Radius [number] Default: 5 Morphological Operation [selection] Options: • 0 — dilate Default: 0 Foreground Value [number] Default: 1 Background Value [number] Default: 0 Outputs Feature Output Image [raster] 18.4. OrfeoToolbox algorithm provider 285 QGIS User Guide, Release 2.6 Console usage processing.runalg(’otb:binarymorphologicaloperationdilate’, -in, -channel, -ram, -structype, -structype.ball.xradius, -filter, -filter.dilate.foreval, -filter.dilate.backval, -out) See also BinaryMorphologicalOperation (erode) Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Structuring Element Type [selection] Options: • 0 — ball Default: 0 The Structuring Element Radius [number] Default: 5 Morphological Operation [selection] Options: • 0 — erode Default: 0 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:binarymorphologicaloperationerode’, -in, -channel, -ram, -structype, -structype.ball.xradius, -filter, -out) See also BinaryMorphologicalOperation (opening) Description 286 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Structuring Element Type [selection] Options: • 0 — ball Default: 0 The Structuring Element Radius [number] Default: 5 Morphological Operation [selection] Options: • 0 — opening Default: 0 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:binarymorphologicaloperationopening’, -in, -channel, -ram, -structype, -structype.ball.xradius, -filter, -out) See also EdgeExtraction (gradient) Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Edge feature [selection] Options: 18.4. OrfeoToolbox algorithm provider 287 QGIS User Guide, Release 2.6 • 0 — gradient Default: 0 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:edgeextractiongradient’, -in, -channel, -ram, -filter, -out) See also EdgeExtraction (sobel) Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Edge feature [selection] Options: • 0 — sobel Default: 0 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:edgeextractionsobel’, -in, -channel, -ram, -filter, -out) See also EdgeExtraction (touzi) Description 288 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Edge feature [selection] Options: • 0 — touzi Default: 0 The Radius [number] Default: 1 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:edgeextractiontouzi’, -in, -channel, -ram, -filter, -filter.touzi.xradius, -out) See also GrayScaleMorphologicalOperation (closing) Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Structuring Element Type [selection] Options: • 0 — ball Default: 0 The Structuring Element Radius [number] Default: 5 18.4. OrfeoToolbox algorithm provider 289 QGIS User Guide, Release 2.6 Morphological Operation [selection] Options: • 0 — closing Default: 0 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:grayscalemorphologicaloperationclosing’, -in, -channel, -ram, -structype, -structype.ball.xradius, -filter, -out) See also GrayScaleMorphologicalOperation (dilate) Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Structuring Element Type [selection] Options: • 0 — ball Default: 0 The Structuring Element Radius [number] Default: 5 Morphological Operation [selection] Options: • 0 — dilate Default: 0 Outputs Feature Output Image [raster] 290 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’otb:grayscalemorphologicaloperationdilate’, -in, -channel, -ram, -structype, -structype.ball.xradius, -filter, -out) See also GrayScaleMorphologicalOperation (erode) Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Structuring Element Type [selection] Options: • 0 — ball Default: 0 The Structuring Element Radius [number] Default: 5 Morphological Operation [selection] Options: • 0 — erode Default: 0 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:grayscalemorphologicaloperationerode’, -in, -channel, -ram, -structype, -structype.ball.xradius, -filter, -out) See also GrayScaleMorphologicalOperation (opening) Description 18.4. OrfeoToolbox algorithm provider 291 QGIS User Guide, Release 2.6 Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Structuring Element Type [selection] Options: • 0 — ball Default: 0 The Structuring Element Radius [number] Default: 5 Morphological Operation [selection] Options: • 0 — opening Default: 0 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:grayscalemorphologicaloperationopening’, -in, -channel, -ram, -structype, -structype.ball.xradius, -filter, -out) See also Haralick Texture Extraction Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 X Radius [number] Default: 2 292 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Y Radius [number] Default: 2 X Offset [number] Default: 1 Y Offset [number] Default: 1 Image Minimum [number] Default: 0 Image Maximum [number] Default: 255 Histogram number of bin [number] Default: 8 Texture Set Selection [selection] Options: • 0 — simple • 1 — advanced • 2 — higher Default: 0 Outputs Output Image [raster] Console usage processing.runalg(’otb:haralicktextureextraction’, -in, -channel, -ram, -parameters.xrad, -parameters.yrad, -parameters.xoff, -parameters.yoff, -parameters.min, -parameters.max, -parameters.nbbin, -texture, -out) See also Line segment detection Description Parameters Input Image [raster] No rescaling in [0, 255] [boolean] Default: True 18.4. OrfeoToolbox algorithm provider 293 QGIS User Guide, Release 2.6 Outputs Output Detected lines [vector] Console usage processing.runalg(’otb:linesegmentdetection’, -in, -norescale, -out) See also Local Statistic Extraction Description Parameters Input Image [raster] Selected Channel [number] Default: 1 Available RAM (Mb) [number] Default: 128 Neighborhood radius [number] Default: 3 Outputs Feature Output Image [raster] Console usage processing.runalg(’otb:localstatisticextraction’, -in, -channel, -ram, -radius, -out) See also Multivariate alteration detector Description 294 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input Image 1 [raster] Input Image 2 [raster] Available RAM (Mb) [number] Default: 128 Outputs Change Map [raster] Console usage processing.runalg(’otb:multivariatealterationdetector’,-in1,-in2,-ram,-out) See also Radiometric Indices Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Blue Channel [number] Default: 1 Green Channel [number] Default: 1 Red Channel [number] Default: 1 NIR Channel [number] Default: 1 Mir Channel [number] Default: 1 Available Radiometric Indices [selection] Options: • 0 — ndvi • 1 — tndvi • 2 — rvi 18.4. OrfeoToolbox algorithm provider 295 QGIS User Guide, Release 2.6 • 3 — savi • 4 — tsavi • 5 — msavi • 6 — msavi2 • 7 — gemi • 8 — ipvi • 9 — ndwi • 10 — ndwi2 • 11 — mndwi • 12 — ndpi • 13 — ndti • 14 — ri • 15 — ci • 16 — bi • 17 — bi2 Default: 0 Outputs Output Image [raster] Console usage processing.runalg(’otb:radiometricindices’, -in, -ram, -channels.blue, -channels.green, -channels.red, -channels.nir, -channels.mir, -list, -out) See also . 18.4.3 Geometry Image Envelope Description Parameters Input Image [raster] Sampling Rate [number] Default: 0 296 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Projection [string] Optional. Default: None Outputs Output Vector Data [vector] Console usage processing.runalg(’otb:imageenvelope’, -in, -sr, -proj, -out) See also OrthoRectification (epsg) Description Parameters Input Image [raster] Output Cartographic Map Projection [selection] Options: • 0 — epsg Default: 0 EPSG Code [number] Default: 4326 Parameters estimation modes [selection] Options: • 0 — autosize • 1 — autospacing Default: 0 Default pixel value [number] Default: 0 Default elevation [number] Default: 0 Interpolation [selection] Options: • 0 — bco • 1 — nn • 2 — linear 18.4. OrfeoToolbox algorithm provider 297 QGIS User Guide, Release 2.6 Default: 0 Radius for bicubic interpolation [number] Default: 2 Available RAM (Mb) [number] Default: 128 Resampling grid spacing [number] Default: 4 Outputs Output Image [raster] Console usage processing.runalg(’otb:orthorectificationepsg’, -io.in, -map, -map.epsg.code, -outputs.mode, -outputs.default, -elev.default, -interpolator, -interpolator.bco.radius, -opt.ram, -opt.gridspacing, -io.out) See also OrthoRectification (fit-to-ortho) Description Parameters Input Image [raster] Parameters estimation modes [selection] Options: • 0 — orthofit Default: 0 Model ortho-image [raster] Optional. Default pixel value [number] Default: 0 Default elevation [number] Default: 0 Interpolation [selection] Options: • 0 — bco • 1 — nn • 2 — linear Default: 0 298 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Radius for bicubic interpolation [number] Default: 2 Available RAM (Mb) [number] Default: 128 Resampling grid spacing [number] Default: 4 Outputs Output Image [raster] Console usage processing.runalg(’otb:orthorectificationfittoortho’, -io.in, -outputs.mode, -outputs.ortho, -outputs.default, -elev.default, -interpolator, -interpolator.bco.radius, -opt.ram, -opt.gridspacing, -io.out) See also OrthoRectification (lambert-WGS84) Description Parameters Input Image [raster] Output Cartographic Map Projection [selection] Options: • 0 — lambert2 • 1 — lambert93 • 2 — wgs Default: 0 Parameters estimation modes [selection] Options: • 0 — autosize • 1 — autospacing Default: 0 Default pixel value [number] Default: 0 Default elevation [number] Default: 0 Interpolation [selection] Options: 18.4. OrfeoToolbox algorithm provider 299 QGIS User Guide, Release 2.6 • 0 — bco • 1 — nn • 2 — linear Default: 0 Radius for bicubic interpolation [number] Default: 2 Available RAM (Mb) [number] Default: 128 Resampling grid spacing [number] Default: 4 Outputs Output Image [raster] Console usage processing.runalg(’otb:orthorectificationlambertwgs84’, -io.in, -map, -outputs.mode, -outputs.default, -elev.default, -interpolator, -interpolator.bco.radius, -opt.ram, -opt.gridspacing, -io.out) See also OrthoRectification (utm) Description Parameters Input Image [raster] Output Cartographic Map Projection [selection] Options: • 0 — utm Default: 0 Zone number [number] Default: 31 Northern Hemisphere [boolean] Default: True Parameters estimation modes [selection] Options: • 0 — autosize • 1 — autospacing Default: 0 300 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Default pixel value [number] Default: 0 Default elevation [number] Default: 0 Interpolation [selection] Options: • 0 — bco • 1 — nn • 2 — linear Default: 0 Radius for bicubic interpolation [number] Default: 2 Available RAM (Mb) [number] Default: 128 Resampling grid spacing [number] Default: 4 Outputs Output Image [raster] Console usage processing.runalg(’otb:orthorectificationutm’, -io.in, -map, -map.utm.zone, -map.utm.northhem, -outputs.mode, -outputs.default, -elev.default, -interpolator, -interpolator.bco.radius, -opt.ram, -opt.gridspacing, -io.out) See also Pansharpening (bayes) Description Parameters Input PAN Image [raster] Input XS Image [raster] Algorithm [selection] Options: • 0 — bayes Default: 0 Weight [number] Default: 0.9999 18.4. OrfeoToolbox algorithm provider 301 QGIS User Guide, Release 2.6 S coefficient [number] Default: 1 Available RAM (Mb) [number] Default: 128 Outputs Output image [raster] Console usage processing.runalg(’otb:pansharpeningbayes’, -inp, -inxs, -method, -method.bayes.lambda, -method.bayes.s, -ram, -out) See also Pansharpening (lmvm) Description Parameters Input PAN Image [raster] Input XS Image [raster] Algorithm [selection] Options: • 0 — lmvm Default: 0 X radius [number] Default: 3 Y radius [number] Default: 3 Available RAM (Mb) [number] Default: 128 Outputs Output image [raster] Console usage processing.runalg(’otb:pansharpeninglmvm’,-inp,-inxs,-method,-method.lmvm.radiusx,-method.lmvm.radiusy,-ram,-out) 302 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Pansharpening (rcs) Description Parameters Input PAN Image [raster] Input XS Image [raster] Algorithm [selection] Options: • 0 — rcs Default: 0 Available RAM (Mb) [number] Default: 128 Outputs Output image [raster] Console usage processing.runalg(’otb:pansharpeningrcs’,-inp,-inxs,-method,-ram,-out) See also RigidTransformResample (id) Description Parameters Input image [raster] Type of transformation [selection] Options: • 0 — id Default: 0 X scaling [number] Default: 1 18.4. OrfeoToolbox algorithm provider 303 QGIS User Guide, Release 2.6 Y scaling [number] Default: 1 Interpolation [selection] Options: • 0 — nn • 1 — linear • 2 — bco Default: 2 Radius for bicubic interpolation [number] Default: 2 Available RAM (Mb) [number] Default: 128 Outputs Output image [raster] Console usage processing.runalg(’otb:rigidtransformresampleid’, -in, -transform.type, -transform.type.id.scalex, -transform.type.id.scaley, -interpolator, -interpolator.bco.radius, -ram, -out) See also RigidTransformResample (rotation) Description Parameters Input image [raster] Type of transformation [selection] Options: • 0 — rotation Default: 0 Rotation angle [number] Default: 0 X scaling [number] Default: 1 Y scaling [number] Default: 1 304 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Interpolation [selection] Options: • 0 — nn • 1 — linear • 2 — bco Default: 2 Radius for bicubic interpolation [number] Default: 2 Available RAM (Mb) [number] Default: 128 Outputs Output image [raster] Console usage processing.runalg(’otb:rigidtransformresamplerotation’, -in, -transform.type, -transform.type.rotation.angle, -transform.type.rotation.scalex, -transform.type.rotation.scaley, -interpolator, -interpolator.bco.radius, -ram, -out) See also RigidTransformResample (translation) Description Parameters Input image [raster] Type of transformation [selection] Options: • 0 — translation Default: 0 The X translation (in physical units) [number] Default: 0 The Y translation (in physical units) [number] Default: 0 X scaling [number] Default: 1 Y scaling [number] Default: 1 18.4. OrfeoToolbox algorithm provider 305 QGIS User Guide, Release 2.6 Interpolation [selection] Options: • 0 — nn • 1 — linear • 2 — bco Default: 2 Radius for bicubic interpolation [number] Default: 2 Available RAM (Mb) [number] Default: 128 Outputs Output image [raster] Console usage processing.runalg(’otb:rigidtransformresampletranslation’, -in, -transform.type, -transform.type.translation.tx, -transform.type.translation.ty, -transform.type.translation.scalex, -transform.type.translation.scaley, -interpolator, -interpolator.bco.radius, -ram, -out) See also Superimpose sensor Description Parameters Reference input [raster] The image to reproject [raster] Default elevation [number] Default: 0 Spacing of the deformation field [number] Default: 4 Interpolation [selection] Options: • 0 — bco • 1 — nn • 2 — linear Default: 0 Radius for bicubic interpolation [number] Default: 2 306 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Available RAM (Mb) [number] Default: 128 Outputs Output image [raster] Console usage processing.runalg(’otb:superimposesensor’,-inr,-inm,-elev.default,-lms,-interpolator,-interpolator.bco.radius,-ram,-out) See also . 18.4.4 Image filtering DimensionalityReduction (ica) Description Parameters Input Image [raster] Algorithm [selection] Options: • 0 — ica Default: 0 number of iterations [number] Default: 20 Give the increment weight of W in [0, 1] [number] Default: 1 Number of Components [number] Default: 0 Normalize [boolean] Default: True Outputs Output Image [raster] ‘‘ Inverse Output Image‘‘ [raster] Transformation matrix output [file] 18.4. OrfeoToolbox algorithm provider 307 QGIS User Guide, Release 2.6 Console usage processing.runalg(’otb:dimensionalityreductionica’, -in, -method, -method.ica.iter, -method.ica.mu, -nbcomp, -normalize, -out, -outinv, -outmatrix) See also DimensionalityReduction (maf) Description Parameters Input Image [raster] Algorithm [selection] Options: • 0 — maf Default: 0 Number of Components. [number] Default: 0 Normalize. [boolean] Default: True Outputs Output Image [raster] Transformation matrix output [file] Console usage processing.runalg(’otb:dimensionalityreductionmaf’, -in, -method, -nbcomp, -normalize, -out, -outmatrix) See also DimensionalityReduction (napca) Description 308 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input Image [raster] Algorithm [selection] Options: • 0 — napca Default: 0 Set the x radius of the sliding window. [number] Default: 1 Set the y radius of the sliding window. [number] Default: 1 Number of Components. [number] Default: 0 Normalize. [boolean] Default: True Outputs Output Image [raster] ‘‘ Inverse Output Image‘‘ [raster] Transformation matrix output [file] Console usage processing.runalg(’otb:dimensionalityreductionnapca’, -in, -method, -method.napca.radiusx, -method.napca.radiusy, -nbcomp, -normalize, -out, -outinv, -outmatrix) See also DimensionalityReduction (pca) Description Parameters Input Image [raster] Algorithm [selection] Options: • 0 — pca Default: 0 Number of Components. [number] Default: 0 18.4. OrfeoToolbox algorithm provider 309 QGIS User Guide, Release 2.6 Normalize. [boolean] Default: True Outputs Output Image [raster] ‘‘ Inverse Output Image‘‘ [raster] Transformation matrix output [file] Console usage processing.runalg(’otb:dimensionalityreductionpca’, -in, -method, -nbcomp, -normalize, -out, -outinv, -outmatrix) See also Mean Shift filtering (can be used as Exact Large-Scale Mean-Shift segmentation, step 1) Description Parameters Input Image [raster] Spatial radius [number] Default: 5 Range radius [number] Default: 15 Mode convergence threshold [number] Default: 0.1 Maximum number of iterations [number] Default: 100 Range radius coefficient [number] Default: 0 Mode search. [boolean] Default: True Outputs Filtered output [raster] Spatial image [raster] 310 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’otb:meanshiftfilteringcanbeusedasexactlargescalemeanshiftsegmentationstep1’, -in, -spatialr, -ranger, -thres, -maxiter, -rangeramp, -modesearch, -fout, -foutpos) See also Smoothing (anidif) Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Smoothing Type [selection] Options: • 0 — anidif Default: 2 Time Step [number] Default: 0.125 Nb Iterations [number] Default: 10 Outputs Output Image [raster] Console usage processing.runalg(’otb:smoothinganidif’, -in, -ram, -type, -type.anidif.timestep, -type.anidif.nbiter, -out) See also Smoothing (gaussian) Description 18.4. OrfeoToolbox algorithm provider 311 QGIS User Guide, Release 2.6 Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Smoothing Type [selection] Options: • 0 — gaussian Default: 2 Radius [number] Default: 2 Outputs Output Image [raster] Console usage processing.runalg(’otb:smoothinggaussian’, -in, -ram, -type, -type.gaussian.radius, -out) See also Smoothing (mean) Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Smoothing Type [selection] Options: • 0 — mean Default: 2 Radius [number] Default: 2 Outputs Output Image [raster] 312 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’otb:smoothingmean’, -in, -ram, -type, -type.mean.radius, -out) See also . 18.4.5 Image manipulation ColorMapping (continuous) Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Operation [selection] Options: • 0 — labeltocolor Default: 0 Color mapping method [selection] Options: • 0 — continuous Default: 0 Look-up tables [selection] Options: • 0 — red • 1 — green • 2 — blue • 3 — grey • 4 — hot • 5 — cool • 6 — spring • 7 — summer • 8 — autumn • 9 — winter • 10 — copper 18.4. OrfeoToolbox algorithm provider 313 QGIS User Guide, Release 2.6 • 11 — jet • 12 — hsv • 13 — overunder • 14 — relief Default: 0 Mapping range lower value [number] Default: 0 Mapping range higher value [number] Default: 255 Outputs Output Image [raster] Console usage processing.runalg(’otb:colormappingcontinuous’, -in, -ram, -op, -method, -method.continuous.lut, -method.continuous.min, -method.continuous.max, -out) See also ColorMapping (custom) Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Operation [selection] Options: • 0 — labeltocolor Default: 0 Color mapping method [selection] Options: • 0 — custom Default: 0 Look-up table file [file] 314 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Output Image [raster] Console usage processing.runalg(’otb:colormappingcustom’, -in, -ram, -op, -method, -method.custom.lut, -out) See also ColorMapping (image) Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Operation [selection] Options: • 0 — labeltocolor Default: 0 Color mapping method [selection] Options: • 0 — image Default: 0 Support Image [raster] NoData value [number] Default: 0 lower quantile [number] Default: 2 upper quantile [number] Default: 2 Outputs Output Image [raster] 18.4. OrfeoToolbox algorithm provider 315 QGIS User Guide, Release 2.6 Console usage processing.runalg(’otb:colormappingimage’, -in, -ram, -op, -method, -method.image.in, -method.image.nodatavalue, -method.image.low, -method.image.up, -out) See also ColorMapping (optimal) Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Operation [selection] Options: • 0 — labeltocolor Default: 0 Color mapping method [selection] Options: • 0 — optimal Default: 0 Background label [number] Default: 0 Outputs Output Image [raster] Console usage processing.runalg(’otb:colormappingoptimal’, -in, -ram, -op, -method, -method.optimal.background, -out) See also ExtractROI (fit) Description 316 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Extraction mode [selection] Options: • 0 — fit Default: 0 Reference image [raster] Default elevation [number] Default: 0 Outputs Output Image [raster] Console usage processing.runalg(’otb:extractroifit’, -in, -ram, -mode, -mode.fit.ref, -mode.fit.elev.default, -out) See also ExtractROI (standard) Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Extraction mode [selection] Options: • 0 — standard Default: 0 Start X [number] Default: 0 Start Y [number] Default: 0 18.4. OrfeoToolbox algorithm provider 317 QGIS User Guide, Release 2.6 Size X [number] Default: 0 Size Y [number] Default: 0 Outputs Output Image [raster] Console usage processing.runalg(’otb:extractroistandard’, -in, -ram, -mode, -startx, -starty, -sizex, -sizey, -out) See also Images Concatenation Description Parameters Input images list [multipleinput: rasters] Available RAM (Mb) [number] Default: 128 Outputs Output Image [raster] Console usage processing.runalg(’otb:imagesconcatenation’,-il,-ram,-out) See also Image Tile Fusion Description 318 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input Tile Images [multipleinput: rasters] Number of tile columns [number] Default: 0 Number of tile rows [number] Default: 0 Outputs Output Image [raster] Console usage processing.runalg(’otb:imagetilefusion’,-il,-cols,-rows,-out) See also Read image information Description Parameters Input Image [raster] Display the OSSIM keywordlist [boolean] Default: True GCPs Id [string] Default: None GCPs Info [string] Default: None GCPs Image Coordinates [string] Default: None GCPs Geographic Coordinates [string] Default: None Outputs Console usage processing.runalg(’otb:readimageinformation’, -in, -keywordlist, -gcp.ids, -gcp.info, -gcp.imcoord, -gcp.geocoord) 18.4. OrfeoToolbox algorithm provider 319 QGIS User Guide, Release 2.6 See also Rescale Image Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Output min value [number] Default: 0 Output max value [number] Default: 255 Outputs Output Image [raster] Console usage processing.runalg(’otb:rescaleimage’, -in, -ram, -outmin, -outmax, -out) See also Split Image Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Outputs Output Image [file] 320 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’otb:splitimage’, -in, -ram, -out) See also . 18.4.6 Learning Classification Map Regularization Description Parameters Input classification image [raster] Structuring element radius (in pixels) [number] Default: 1 Multiple majority: Undecided(X)/Original [boolean] Default: True Label for the NoData class [number] Default: 0 Label for the Undecided class [number] Default: 0 Available RAM (Mb) [number] Default: 128 Outputs Output regularized image [raster] Console usage processing.runalg(’otb:classificationmapregularization’, -io.in, -ip.radius, -ip.suvbool, -ip.nodatalabel, -ip.undecidedlabel, -ram, -io.out) See also ComputeConfusionMatrix (raster) Description 18.4. OrfeoToolbox algorithm provider 321 QGIS User Guide, Release 2.6 Parameters Input Image [raster] Ground truth [selection] Options: • 0 — raster Default: 0 Input reference image [raster] Value for nodata pixels [number] Default: 0 Available RAM (Mb) [number] Default: 128 Outputs Matrix output [file] Console usage processing.runalg(’otb:computeconfusionmatrixraster’, -in, -ref, -ref.raster.in, -nodatalabel, -ram, -out) See also ComputeConfusionMatrix (vector) Description Parameters Input Image [raster] Ground truth [selection] Options: • 0 — vector Default: 0 Input reference vector data [file] Field name [string] Optional. Default: Class Value for nodata pixels [number] Default: 0 322 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Available RAM (Mb) [number] Default: 128 Outputs Matrix output [file] Console usage processing.runalg(’otb:computeconfusionmatrixvector’, -in, -ref, -ref.vector.in, -ref.vector.field, -nodatalabel, -ram, -out) See also Compute Images second order statistics Description Parameters Input images [multipleinput: rasters] Background Value [number] Default: 0.0 Outputs Output XML file [file] Console usage processing.runalg(’otb:computeimagessecondorderstatistics’,-il,-bv,-out) See also FusionOfClassifications (dempstershafer) Description Parameters Input classifications [multipleinput: rasters] Fusion method [selection] Options: 18.4. OrfeoToolbox algorithm provider 323 QGIS User Guide, Release 2.6 • 0 — dempstershafer Default: 0 Confusion Matrices [multipleinput: files] Mass of belief measurement [selection] Options: • 0 — precision • 1 — recall • 2 — accuracy • 3 — kappa Default: 0 Label for the NoData class [number] Default: 0 Label for the Undecided class [number] Default: 0 Outputs The output classification image [raster] Console usage processing.runalg(’otb:fusionofclassificationsdempstershafer’,-il,-method,-method.dempstershafer.cmfl,-method.dempstershafer.mob,-nodatalabel,-undecidedlabel,-out) See also FusionOfClassifications (majorityvoting) Description Parameters Input classifications [multipleinput: rasters] Fusion method [selection] Options: • 0 — majorityvoting Default: 0 Label for the NoData class [number] Default: 0 Label for the Undecided class [number] Default: 0 324 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs The output classification image [raster] Console usage processing.runalg(’otb:fusionofclassificationsmajorityvoting’,-il,-method,-nodatalabel,-undecidedlabel,-out) See also Image Classification Description Parameters Input Image [raster] Input Mask [raster] Optional. Model file [file] Statistics file [file] Optional. Available RAM (Mb) [number] Default: 128 Outputs Output Image [raster] Console usage processing.runalg(’otb:imageclassification’, -in, -mask, -model, -imstat, -ram, -out) See also SOM Classification Description 18.4. OrfeoToolbox algorithm provider 325 QGIS User Guide, Release 2.6 Parameters InputImage [raster] ValidityMask [raster] Optional. TrainingProbability [number] Default: 1 TrainingSetSize [number] Default: 0 StreamingLines [number] Default: 0 SizeX [number] Default: 32 SizeY [number] Default: 32 NeighborhoodX [number] Default: 10 NeighborhoodY [number] Default: 10 NumberIteration [number] Default: 5 BetaInit [number] Default: 1 BetaFinal [number] Default: 0.1 InitialValue [number] Default: 0 Available RAM (Mb) [number] Default: 128 set user defined seed [number] Default: 0 Outputs OutputImage [raster] SOM Map [raster] Console usage processing.runalg(’otb:somclassification’, -in, -vm, -tp, -ts, -sl, -sx, -sy, -nx, -ny, -ni, -bi, -bf, -iv, -ram, -rand, -out, -som) 326 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also TrainImagesClassifier (ann) Description Parameters Input Image List [multipleinput: rasters] Input Vector Data List [multipleinput: any vectors] Input XML image statistics file [file] Optional. Default elevation [number] Default: 0 Maximum training sample size per class [number] Default: 1000 Maximum validation sample size per class [number] Default: 1000 On edge pixel inclusion [boolean] Default: True Training and validation sample ratio [number] Default: 0.5 Name of the discrimination field [string] Default: Class Classifier to use for the training [selection] Options: • 0 — ann Default: 0 Train Method Type [selection] Options: • 0 — reg • 1 — back Default: 0 Number of neurons in each intermediate layer [string] Default: None Neuron activation function type [selection] Options: • 0 — ident • 1 — sig 18.4. OrfeoToolbox algorithm provider 327 QGIS User Guide, Release 2.6 • 2 — gau Default: 1 Alpha parameter of the activation function [number] Default: 1 Beta parameter of the activation function [number] Default: 1 Strength of the weight gradient term in the BACKPROP method [number] Default: 0.1 Strength of the momentum term (the difference between weights on the 2 previous iterations) [number] Default: 0.1 Initial value Delta_0 of update-values Delta_{ij} in RPROP method [number] Default: 0.1 Update-values lower limit Delta_{min} in RPROP method [number] Default: 1e-07 Termination criteria [selection] Options: • 0 — iter • 1 — eps • 2 — all Default: 2 Epsilon value used in the Termination criteria [number] Default: 0.01 Maximum number of iterations used in the Termination criteria [number] Default: 1000 set user defined seed [number] Default: 0 Outputs Output confusion matrix [file] Output model [file] Console usage processing.runalg(’otb:trainimagesclassifierann’,-io.il,-io.vd,-io.imstat,-elev.default,-sample.mt,-sample.mv,-sample.edg,-sample.vtr,-sample.vfn,-classifier,-classifier.ann.t,-classifier.ann.sizes,-classifier.ann.f,-classifier.ann.a,-classifier.ann.b,-classifier.ann.bpdw,-classifier.ann.bpms,-classifier.ann.rdw,-classifier.ann.rdwm,-classifier.ann.term,-classifier.ann.eps,-classifier.ann.iter,-rand,-io.confmatout,-io.out) 328 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also TrainImagesClassifier (bayes) Description Parameters Input Image List [multipleinput: rasters] Input Vector Data List [multipleinput: any vectors] Input XML image statistics file [file] Optional. Default elevation [number] Default: 0 Maximum training sample size per class [number] Default: 1000 Maximum validation sample size per class [number] Default: 1000 On edge pixel inclusion [boolean] Default: True Training and validation sample ratio [number] Default: 0.5 Name of the discrimination field [string] Default: Class Classifier to use for the training [selection] Options: • 0 — bayes Default: 0 set user defined seed [number] Default: 0 Outputs Output confusion matrix [file] Output model [file] Console usage processing.runalg(’otb:trainimagesclassifierbayes’,-io.il,-io.vd,-io.imstat,-elev.default,-sample.mt,-sample.mv,-sample.edg,-sample.vtr,-sample.vfn,-classifier,-rand,-io.confmatout,-io.out) 18.4. OrfeoToolbox algorithm provider 329 QGIS User Guide, Release 2.6 See also TrainImagesClassifier (boost) Description Parameters Input Image List [multipleinput: rasters] Input Vector Data List [multipleinput: any vectors] Input XML image statistics file [file] Optional. Default elevation [number] Default: 0 Maximum training sample size per class [number] Default: 1000 Maximum validation sample size per class [number] Default: 1000 On edge pixel inclusion [boolean] Default: True Training and validation sample ratio [number] Default: 0.5 Name of the discrimination field [string] Default: Class Classifier to use for the training [selection] Options: • 0 — boost Default: 0 Boost Type [selection] Options: • 0 — discrete • 1 — real • 2 — logit • 3 — gentle Default: 1 Weak count [number] Default: 100 Weight Trim Rate [number] Default: 0.95 330 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Maximum depth of the tree [number] Default: 1 set user defined seed [number] Default: 0 Outputs Output confusion matrix [file] Output model [file] Console usage processing.runalg(’otb:trainimagesclassifierboost’,-io.il,-io.vd,-io.imstat,-elev.default,-sample.mt,-sample.mv,-sample.edg,-sample.vtr,-sample.vfn,-classifier,-classifier.boost.t,-classifier.boost.w,-classifier.boost.r,-classifier.boost.m,-rand,-io.confmatout,-io.out) See also TrainImagesClassifier (dt) Description Parameters Input Image List [multipleinput: rasters] Input Vector Data List [multipleinput: any vectors] Input XML image statistics file [file] Optional. Default elevation [number] Default: 0 Maximum training sample size per class [number] Default: 1000 Maximum validation sample size per class [number] Default: 1000 On edge pixel inclusion [boolean] Default: True Training and validation sample ratio [number] Default: 0.5 Name of the discrimination field [string] Default: Class Classifier to use for the training [selection] Options: • 0 — dt 18.4. OrfeoToolbox algorithm provider 331 QGIS User Guide, Release 2.6 Default: 0 Maximum depth of the tree [number] Default: 65535 Minimum number of samples in each node [number] Default: 10 Termination criteria for regression tree [number] Default: 0.01 Cluster possible values of a categorical variable into K <= cat clusters to find a suboptimal split [number] Default: 10 K-fold cross-validations [number] Default: 10 Set Use1seRule flag to false [boolean] Default: True Set TruncatePrunedTree flag to false [boolean] Default: True set user defined seed [number] Default: 0 Outputs Output confusion matrix [file] Output model [file] Console usage processing.runalg(’otb:trainimagesclassifierdt’,-io.il,-io.vd,-io.imstat,-elev.default,-sample.mt,-sample.mv,-sample.edg,-sample.vtr,-sample.vfn,-classifier,-classifier.dt.max,-classifier.dt.min,-classifier.dt.ra,-classifier.dt.cat,-classifier.dt.f,-classifier.dt.r,-classifier.dt.t,-rand,-io.confmatout,-io.out) See also TrainImagesClassifier (gbt) Description Parameters Input Image List [multipleinput: rasters] Input Vector Data List [multipleinput: any vectors] Input XML image statistics file [file] Optional. 332 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Default elevation [number] Default: 0 Maximum training sample size per class [number] Default: 1000 Maximum validation sample size per class [number] Default: 1000 On edge pixel inclusion [boolean] Default: True Training and validation sample ratio [number] Default: 0.5 Name of the discrimination field [string] Default: Class Classifier to use for the training [selection] Options: • 0 — gbt Default: 0 Number of boosting algorithm iterations [number] Default: 200 Regularization parameter [number] Default: 0.01 Portion of the whole training set used for each algorithm iteration [number] Default: 0.8 Maximum depth of the tree [number] Default: 3 set user defined seed [number] Default: 0 Outputs Output confusion matrix [file] Output model [file] Console usage processing.runalg(’otb:trainimagesclassifiergbt’,-io.il,-io.vd,-io.imstat,-elev.default,-sample.mt,-sample.mv,-sample.edg,-sample.vtr,-sample.vfn,-classifier,-classifier.gbt.w,-classifier.gbt.s,-classifier.gbt.p,-classifier.gbt.max,-rand,-io.confmatout,-io.out) 18.4. OrfeoToolbox algorithm provider 333 QGIS User Guide, Release 2.6 See also TrainImagesClassifier (knn) Description Parameters Input Image List [multipleinput: rasters] Input Vector Data List [multipleinput: any vectors] Input XML image statistics file [file] Optional. Default elevation [number] Default: 0 Maximum training sample size per class [number] Default: 1000 Maximum validation sample size per class [number] Default: 1000 On edge pixel inclusion [boolean] Default: True Training and validation sample ratio [number] Default: 0.5 Name of the discrimination field [string] Default: Class Classifier to use for the training [selection] Options: • 0 — knn Default: 0 Number of Neighbors [number] Default: 32 set user defined seed [number] Default: 0 Outputs Output confusion matrix [file] Output model [file] 334 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’otb:trainimagesclassifierknn’,-io.il,-io.vd,-io.imstat,-elev.default,-sample.mt,-sample.mv,-sample.edg,-sample.vtr,-sample.vfn,-classifier,-classifier.knn.k,-rand,-io.confmatout,-io.out) See also TrainImagesClassifier (libsvm) Description Parameters Input Image List [multipleinput: rasters] Input Vector Data List [multipleinput: any vectors] Input XML image statistics file [file] Optional. Default elevation [number] Default: 0 Maximum training sample size per class [number] Default: 1000 Maximum validation sample size per class [number] Default: 1000 On edge pixel inclusion [boolean] Default: True Training and validation sample ratio [number] Default: 0.5 Name of the discrimination field [string] Default: Class Classifier to use for the training [selection] Options: • 0 — libsvm Default: 0 SVM Kernel Type [selection] Options: • 0 — linear • 1 — rbf • 2 — poly • 3 — sigmoid Default: 0 18.4. OrfeoToolbox algorithm provider 335 QGIS User Guide, Release 2.6 Cost parameter C [number] Default: 1 Parameters optimization [boolean] Default: True set user defined seed [number] Default: 0 Outputs Output confusion matrix [file] Output model [file] Console usage processing.runalg(’otb:trainimagesclassifierlibsvm’,-io.il,-io.vd,-io.imstat,-elev.default,-sample.mt,-sample.mv,-sample.edg,-sample.vtr,-sample.vfn,-classifier,-classifier.libsvm.k,-classifier.libsvm.c,-classifier.libsvm.opt,-rand,-io.confmatout,-io.out) See also TrainImagesClassifier (rf) Description Parameters Input Image List [multipleinput: rasters] Input Vector Data List [multipleinput: any vectors] Input XML image statistics file [file] Optional. Default elevation [number] Default: 0 Maximum training sample size per class [number] Default: 1000 Maximum validation sample size per class [number] Default: 1000 On edge pixel inclusion [boolean] Default: True Training and validation sample ratio [number] Default: 0.5 Name of the discrimination field [string] Default: Class 336 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Classifier to use for the training [selection] Options: • 0 — rf Default: 0 Maximum depth of the tree [number] Default: 5 Minimum number of samples in each node [number] Default: 10 Termination Criteria for regression tree [number] Default: 0 Cluster possible values of a categorical variable into K <= cat clusters to find a suboptimal split [number] Default: 10 Size of the randomly selected subset of features at each tree node [number] Default: 0 Maximum number of trees in the forest [number] Default: 100 Sufficient accuracy (OOB error) [number] Default: 0.01 set user defined seed [number] Default: 0 Outputs Output confusion matrix [file] Output model [file] Console usage processing.runalg(’otb:trainimagesclassifierrf’,-io.il,-io.vd,-io.imstat,-elev.default,-sample.mt,-sample.mv,-sample.edg,-sample.vtr,-sample.vfn,-classifier,-classifier.rf.max,-classifier.rf.min,-classifier.rf.ra,-classifier.rf.cat,-classifier.rf.var,-classifier.rf.nbtrees,-classifier.rf.acc,-rand,-io.confmatout,-io.out) See also TrainImagesClassifier (svm) Description 18.4. OrfeoToolbox algorithm provider 337 QGIS User Guide, Release 2.6 Parameters Input Image List [multipleinput: rasters] Input Vector Data List [multipleinput: any vectors] Input XML image statistics file [file] Optional. Default elevation [number] Default: 0 Maximum training sample size per class [number] Default: 1000 Maximum validation sample size per class [number] Default: 1000 On edge pixel inclusion [boolean] Default: True Training and validation sample ratio [number] Default: 0.5 Name of the discrimination field [string] Default: Class Classifier to use for the training [selection] Options: • 0 — svm Default: 0 SVM Model Type [selection] Options: • 0 — csvc • 1 — nusvc • 2 — oneclass Default: 0 SVM Kernel Type [selection] Options: • 0 — linear • 1 — rbf • 2 — poly • 3 — sigmoid Default: 0 Cost parameter C [number] Default: 1 Parameter nu of a SVM optimization problem (NU_SVC / ONE_CLASS) [number] Default: 0 338 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameter coef0 of a kernel function (POLY / SIGMOID) [number] Default: 0 Parameter gamma of a kernel function (POLY / RBF / SIGMOID) [number] Default: 1 Parameter degree of a kernel function (POLY) [number] Default: 1 Parameters optimization [boolean] Default: True set user defined seed [number] Default: 0 Outputs Output confusion matrix [file] Output model [file] Console usage processing.runalg(’otb:trainimagesclassifiersvm’,-io.il,-io.vd,-io.imstat,-elev.default,-sample.mt,-sample.mv,-sample.edg,-sample.vtr,-sample.vfn,-classifier,-classifier.svm.m,-classifier.svm.k,-classifier.svm.c,-classifier.svm.nu,-classifier.svm.coef0,-classifier.svm.gamma,-classifier.svm.degree,-classifier.svm.opt,-rand,-io.confmatout,-io.out) See also Unsupervised KMeans image classification Description Parameters Input Image [raster] Available RAM (Mb) [number] Default: 128 Validity Mask [raster] Optional. Training set size [number] Default: 100 Number of classes [number] Default: 5 Maximum number of iterations [number] Default: 1000 18.4. OrfeoToolbox algorithm provider 339 QGIS User Guide, Release 2.6 Convergence threshold [number] Default: 0.0001 Outputs Output Image [raster] Centroid filename [file] Console usage processing.runalg(’otb:unsupervisedkmeansimageclassification’, -in, -ram, -vm, -ts, -nc, -maxit, -ct, -out, -outmeans) See also . 18.4.7 Miscellaneous Band Math Description Parameters Input image list [multipleinput: rasters] Available RAM (Mb) [number] Default: 128 Expression [string] Default: None Outputs Output Image [raster] Console usage processing.runalg(’otb:bandmath’,-il,-ram,-exp,-out) See also ComputeModulusAndPhase-one (OneEntry) Description 340 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Number Of inputs [selection] Options: • 0 — one Default: 0 Input image [raster] Available RAM (Mb) [number] Default: 128 Outputs Modulus [raster] Phase [raster] Console usage processing.runalg(’otb:computemodulusandphaseoneoneentry’, -nbinput, -nbinput.one.in, -ram, -mod, -pha) See also ComputeModulusAndPhase-two (TwoEntries) Description Parameters Number Of inputs [selection] Options: • 0 — two Default: 0 Real part input [raster] Imaginary part input [raster] Available RAM (Mb) [number] Default: 128 Outputs Modulus [raster] Phase [raster] 18.4. OrfeoToolbox algorithm provider 341 QGIS User Guide, Release 2.6 Console usage processing.runalg(’otb:computemodulusandphasetwotwoentries’,-nbinput,-nbinput.two.re,-nbinput.two.im,-ram,-mod,-pha) See also Images comparaison Description Parameters Reference image [raster] Reference image channel [number] Default: 1 Measured image [raster] Measured image channel [number] Default: 1 Start X [number] Default: 0 Start Y [number] Default: 0 Size X [number] Default: 0 Size Y [number] Default: 0 Outputs Console usage processing.runalg(’otb:imagescomparaison’, -ref.in, -ref.channel, -meas.in, -meas.channel, -roi.startx, -roi.starty, -roi.sizex, -roi.sizey) See also Image to KMZ Export Description 342 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input image [raster] Tile Size [number] Default: 512 Image logo [raster] Optional. Image legend [raster] Optional. Default elevation [number] Default: 0 Outputs Output .kmz product [file] Console usage processing.runalg(’otb:imagetokmzexport’, -in, -tilesize, -logo, -legend, -elev.default, -out) See also . 18.4.8 Segmentation Connected Component Segmentation Description Parameters Input Image [raster] Mask expression [string] Optional. Default: None Connected Component Expression [string] Default: None Minimum Object Size [number] Default: 2 18.4. OrfeoToolbox algorithm provider 343 QGIS User Guide, Release 2.6 OBIA Expression [string] Optional. Default: None Default elevation [number] Default: 0 Outputs Output Shape [vector] Console usage processing.runalg(’otb:connectedcomponentsegmentation’, -in, -mask, -expr, -minsize, -obia, -elev.default, -out) See also Exact Large-Scale Mean-Shift segmentation, step 2 Description Parameters Filtered image [raster] Spatial image [raster] Optional. Range radius [number] Default: 15 Spatial radius [number] Default: 5 Minimum Region Size [number] Default: 0 Size of tiles in pixel (X-axis) [number] Default: 500 Size of tiles in pixel (Y-axis) [number] Default: 500 Directory where to write temporary files [file] Optional. Temporary files cleaning [boolean] Default: True 344 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Output Image [raster] Console usage processing.runalg(’otb:exactlargescalemeanshiftsegmentationstep2’, -in, -inpos, -ranger, -spatialr, -minsize, -tilesizex, -tilesizey, -tmpdir, -cleanup, -out) See also Exact Large-Scale Mean-Shift segmentation, step 3 (optional) Description Parameters Input image [raster] Segmented image [raster] Minimum Region Size [number] Default: 50 Size of tiles in pixel (X-axis) [number] Default: 500 Size of tiles in pixel (Y-axis) [number] Default: 500 Outputs Output Image [raster] Console usage processing.runalg(’otb:exactlargescalemeanshiftsegmentationstep3optional’, -in, -inseg, -minsize, -tilesizex, -tilesizey, -out) See also Exact Large-Scale Mean-Shift segmentation, step 4 Description 18.4. OrfeoToolbox algorithm provider 345 QGIS User Guide, Release 2.6 Parameters Input Image [raster] Segmented image [raster] Size of tiles in pixel (X-axis) [number] Default: 500 Size of tiles in pixel (Y-axis) [number] Default: 500 Outputs Output GIS vector file [vector] Console usage processing.runalg(’otb:exactlargescalemeanshiftsegmentationstep4’, -in, -inseg, -tilesizex, -tilesizey, -out) See also Hoover compare segmentation Description Parameters Input ground truth [raster] Input machine segmentation [raster] Background label [number] Default: 0 Overlapping threshold [number] Default: 0.75 Correct detection score [number] Default: 0.0 Over-segmentation score [number] Default: 0.0 Under-segmentation score [number] Default: 0.0 Missed detection score [number] Default: 0.0 346 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Colored ground truth output [raster] Colored machine segmentation output [raster] Console usage processing.runalg(’otb:hoovercomparesegmentation’,-ingt,-inms,-bg,-th,-rc,-rf,-ra,-rm,-outgt,-outms) See also Segmentation (cc) Description Parameters Input Image [raster] Segmentation algorithm [selection] Options: • 0 — cc Default: 0 Condition [string] Default: None Processing mode [selection] Options: • 0 — vector Default: 0 Writing mode for the output vector file [selection] Options: • 0 — ulco • 1 — ovw • 2 — ulovw • 3 — ulu Default: 0 Mask Image [raster] Optional. 8-neighbor connectivity [boolean] Default: True 18.4. OrfeoToolbox algorithm provider 347 QGIS User Guide, Release 2.6 Stitch polygons [boolean] Default: True Minimum object size [number] Default: 1 Simplify polygons [number] Default: 0.1 Layer name [string] Default: layer Geometry index field name [string] Default: DN Tiles size [number] Default: 1024 Starting geometry index [number] Default: 1 OGR options for layer creation [string] Optional. Default: None Outputs Output vector file [vector] Console usage processing.runalg(’otb:segmentationcc’, -in, -filter, -filter.cc.expr, -mode, -mode.vector.outmode, -mode.vector.inmask, -mode.vector.neighbor, -mode.vector.stitch, -mode.vector.minsize, -mode.vector.simplify, -mode.vector.layername, -mode.vector.fieldname, -mode.vector.tilesize, -mode.vector.startlabel, -mode.vector.ogroptions, -mode.vector.out) See also Segmentation (edison) Description Parameters Input Image [raster] Segmentation algorithm [selection] Options: • 0 — edison Default: 0 Spatial radius [number] Default: 5 348 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Range radius [number] Default: 15 Minimum region size [number] Default: 100 Scale factor [number] Default: 1 Processing mode [selection] Options: • 0 — vector Default: 0 Writing mode for the output vector file [selection] Options: • 0 — ulco • 1 — ovw • 2 — ulovw • 3 — ulu Default: 0 Mask Image [raster] Optional. 8-neighbor connectivity [boolean] Default: True Stitch polygons [boolean] Default: True Minimum object size [number] Default: 1 Simplify polygons [number] Default: 0.1 Layer name [string] Default: layer Geometry index field name [string] Default: DN Tiles size [number] Default: 1024 Starting geometry index [number] Default: 1 OGR options for layer creation [string] Optional. Default: None 18.4. OrfeoToolbox algorithm provider 349 QGIS User Guide, Release 2.6 Outputs Output vector file [vector] Console usage processing.runalg(’otb:segmentationedison’, -in, -filter, -filter.edison.spatialr, -filter.edison.ranger, -filter.edison.minsize, -filter.edison.scale, -mode, -mode.vector.outmode, -mode.vector.inmask, -mode.vector.neighbor, -mode.vector.stitch, -mode.vector.minsize, -mode.vector.simplify, -mode.vector.layername, -mode.vector.fieldname, -mode.vector.tilesize, -mode.vector.startlabel, -mode.vector.ogroptions, -mode.vector.out) See also Segmentation (meanshift) Description Parameters Input Image [raster] Segmentation algorithm [selection] Options: • 0 — meanshift Default: 0 Spatial radius [number] Default: 5 Range radius [number] Default: 15 Mode convergence threshold [number] Default: 0.1 Maximum number of iterations [number] Default: 100 Minimum region size [number] Default: 100 Processing mode [selection] Options: • 0 — vector Default: 0 Writing mode for the output vector file [selection] Options: • 0 — ulco • 1 — ovw • 2 — ulovw 350 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 3 — ulu Default: 0 Mask Image [raster] Optional. 8-neighbor connectivity [boolean] Default: True Stitch polygons [boolean] Default: True Minimum object size [number] Default: 1 Simplify polygons [number] Default: 0.1 Layer name [string] Default: layer Geometry index field name [string] Default: DN Tiles size [number] Default: 1024 Starting geometry index [number] Default: 1 OGR options for layer creation [string] Optional. Default: None Outputs Output vector file [vector] Console usage processing.runalg(’otb:segmentationmeanshift’, -in, -filter, -filter.meanshift.spatialr, -filter.meanshift.ranger, -filter.meanshift.thres, -filter.meanshift.maxiter, -filter.meanshift.minsize, -mode, -mode.vector.outmode, -mode.vector.inmask, -mode.vector.neighbor, -mode.vector.stitch, -mode.vector.minsize, -mode.vector.simplify, -mode.vector.layername, -mode.vector.fieldname, -mode.vector.tilesize, -mode.vector.startlabel, -mode.vector.ogroptions, -mode.vector.out) See also Segmentation (mprofiles) Description 18.4. OrfeoToolbox algorithm provider 351 QGIS User Guide, Release 2.6 Parameters Input Image [raster] Segmentation algorithm [selection] Options: • 0 — mprofiles Default: 0 Profile Size [number] Default: 5 Initial radius [number] Default: 1 Radius step. [number] Default: 1 Threshold of the final decision rule [number] Default: 1 Processing mode [selection] Options: • 0 — vector Default: 0 Writing mode for the output vector file [selection] Options: • 0 — ulco • 1 — ovw • 2 — ulovw • 3 — ulu Default: 0 Mask Image [raster] Optional. 8-neighbor connectivity [boolean] Default: True Stitch polygons [boolean] Default: True Minimum object size [number] Default: 1 Simplify polygons [number] Default: 0.1 Layer name [string] Default: layer 352 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Geometry index field name [string] Default: DN Tiles size [number] Default: 1024 Starting geometry index [number] Default: 1 OGR options for layer creation [string] Optional. Default: None Outputs Output vector file [vector] Console usage processing.runalg(’otb:segmentationmprofiles’, -in, -filter, -filter.mprofiles.size, -filter.mprofiles.start, -filter.mprofiles.step, -filter.mprofiles.sigma, -mode, -mode.vector.outmode, -mode.vector.inmask, -mode.vector.neighbor, -mode.vector.stitch, -mode.vector.minsize, -mode.vector.simplify, -mode.vector.layername, -mode.vector.fieldname, -mode.vector.tilesize, -mode.vector.startlabel, -mode.vector.ogroptions, -mode.vector.out) See also Segmentation (watershed) Description Parameters Input Image [raster] Segmentation algorithm [selection] Options: • 0 — watershed Default: 0 Depth Threshold [number] Default: 0.01 Flood Level [number] Default: 0.1 Processing mode [selection] Options: • 0 — vector Default: 0 Writing mode for the output vector file [selection] Options: 18.4. OrfeoToolbox algorithm provider 353 QGIS User Guide, Release 2.6 • 0 — ulco • 1 — ovw • 2 — ulovw • 3 — ulu Default: 0 Mask Image [raster] Optional. 8-neighbor connectivity [boolean] Default: True Stitch polygons [boolean] Default: True Minimum object size [number] Default: 1 Simplify polygons [number] Default: 0.1 Layer name [string] Default: layer Geometry index field name [string] Default: DN Tiles size [number] Default: 1024 Starting geometry index [number] Default: 1 OGR options for layer creation [string] Optional. Default: None Outputs Output vector file [vector] Console usage processing.runalg(’otb:segmentationwatershed’, -in, -filter, -filter.watershed.threshold, -filter.watershed.level, -mode, -mode.vector.outmode, -mode.vector.inmask, -mode.vector.neighbor, -mode.vector.stitch, -mode.vector.minsize, -mode.vector.simplify, -mode.vector.layername, -mode.vector.fieldname, -mode.vector.tilesize, -mode.vector.startlabel, -mode.vector.ogroptions, -mode.vector.out) See also . 354 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 18.4.9 Stereo Stereo Framework Description Parameters Input images list [multipleinput: rasters] Couples list [string] Optional. Default: None Image channel used for the block matching [number] Default: 1 Default elevation [number] Default: 0 Output resolution [number] Default: 1 NoData value [number] Default: -32768 Method to fuse measures in each DSM cell [selection] Options: • 0 — max • 1 — min • 2 — mean • 3 — acc Default: 0 Parameters estimation modes [selection] Options: • 0 — fit • 1 — user Default: 0 Upper Left X [number] Default: 0.0 Upper Left Y [number] Default: 0.0 Size X [number] Default: 0 18.4. OrfeoToolbox algorithm provider 355 QGIS User Guide, Release 2.6 Size Y [number] Default: 0 Pixel Size X [number] Default: 0.0 Pixel Size Y [number] Default: 0.0 Output Cartographic Map Projection [selection] Options: • 0 — utm • 1 — lambert2 • 2 — lambert93 • 3 — wgs • 4 — epsg Default: 3 Zone number [number] Default: 31 Northern Hemisphere [boolean] Default: True EPSG Code [number] Default: 4326 Step of the deformation grid (in pixels) [number] Default: 16 Sub-sampling rate for epipolar grid inversion [number] Default: 10 Block-matching metric [selection] Options: • 0 — ssdmean • 1 — ssd • 2 — ncc • 3 — lp Default: 0 p value [number] Default: 1 Radius of blocks for matching filter (in pixels) [number] Default: 2 Minimum altitude offset (in meters) [number] Default: -20 356 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Maximum altitude offset (in meters) [number] Default: 20 Use bijection consistency in block matching strategy [boolean] Default: True Use median disparities filtering [boolean] Default: True Correlation metric threshold [number] Default: 0.6 Input left mask [raster] Optional. Input right mask [raster] Optional. Discard pixels with low local variance [number] Default: 50 Available RAM (Mb) [number] Default: 128 Outputs Output DSM [raster] Console usage processing.runalg(’otb:stereoframework’,-input.il,-input.co,-input.channel,-elev.default,-output.res,-output.nodata,-output.fusionmethod,-output.mode,-output.mode.user.ulx,-output.mode.user.uly,-output.mode.user.sizex,-output.mode.user.sizey,-output.mode.user.spacingx,-output.mode.user.spacingy,-map,-map.utm.zone,-map.utm.northhem,-map.epsg.code,-stereorect.fwdgridstep,-stereorect.invgridssrate,-bm.metric,-bm.metric.lp.p,-bm.radius,-bm.minhoffset,-bm.maxhoffset,-postproc.bij,-postproc.med,-postproc.metrict,-mask.left,-mask.right,-mask.variancet,-ram,-output.out) See also . 18.4.10 Vector Concatenate Description Parameters Input VectorDatas to concatenate [multipleinput: any vectors] 18.4. OrfeoToolbox algorithm provider 357 QGIS User Guide, Release 2.6 Outputs Concatenated VectorData [vector] Console usage processing.runalg(’otb:concatenate’,-vd,-out) See also . 18.5 QGIS algorithm provider QGIS algortihm provider implements various analysis and geoprocessing operations using mostly only QGIS API. So almost all algorthms from this provider will work “out of the box” without any additional configuration. This provider incorporates fTools functionality, some algorithms from mmQGIS plugin and also adds its own algorithms. . 18.5.1 Database Import into PostGIS Description Parameters Layer to import [vector: any] Database (connection name) [selection] Options: • 0 — local Default: 0 Schema (schema name) [string] Default: public Table to import to (leave blank to use layer name) [string] Default: (not set) Primary key field [tablefield: any] Optional. Geometry column [string] Default: geom 358 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Overwrite [boolean] Default: True Create spatial index [boolean] Default: True Convert field names to lowercase [boolean] Default: True Drop length constraints on character fields [boolean] Default: False Outputs Console usage processing.runalg(’qgis:importintopostgis’, input, database, schema, tablename, primary_key, geometry_column, overwrite, createindex, lowercase_names, drop_string_length) See also PostGIS execute SQL Description Parameters Database [string] Default: (not set) SQL query [string] Default: (not set) Outputs Console usage processing.runalg(’qgis:postgisexecutesql’, database, sql) See also . 18.5. QGIS algorithm provider 359 QGIS User Guide, Release 2.6 18.5.2 Raster general Set style for raster layer Description Parameters Raster layer [raster] Style file [file] Outputs Styled layer [raster] Console usage processing.runalg(’qgis:setstyleforrasterlayer’, input, style) See also . 18.5.3 Raster Hypsometric curves Description Calculate hypsometric curves for features of polygon layer and save them as CSV file for further processing. Parameters DEM to analyze [raster] DEM to use for calculating altitudes. Boundary layer [vector: polygon] Polygonal vector layer with boundaries of areas used to calculate hypso- metric curves. Step [number] Distanse between curves. Default: 100.0 Use % of area instead of absolute value [boolean] Write area percentage to “Area” field of the CSV file instead of absolute area value. Default: False 360 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Output directory [directory] Directory where output will be saved. For each feature from input vector layer CSV file with area and altitude values will be created. File name consists of prefix hystogram_ followed by layer name and feature ID. Console usage processing.runalg(’qgis:hypsometriccurves’, input_dem, boundary_layer, step, use_percentage, output_directory) See also Raster layer statistics Description Calculates basic statistics of the raster layer. Parameters Input layer [raster] Raster to analyze. Outputs Statistics [html] Analysis results in HTML format. Minimum value [number] Minimum cell value. Maximum value [number] Maximum cell value. Sum [number] Sum of all cells values. Mean value [number] Mean cell value. valid cells count [number] Number of cell with data. No-data cells count [number] Number of NODATA cells. Standard deviation [number] Standard deviation of cells values. Console usage processing.runalg(’qgis:rasterlayerstatistics’, input, output_html_file) See also Zonal Statistics Description Calculates some statistics values for pixels of input raster inside certain zones, defined as polygon layer. Following values calculated for each zone: • minimum 18.5. QGIS algorithm provider 361 QGIS User Guide, Release 2.6 • maximum • sum • count • mean • standard deviation • number of unique values • range • variance Parameters Raster layer [raster] Raster to analyze. Raster band [number] Number of raster band to analyze. Default: 1 Vector layer containing zones [vector: polygon] Layer with zones boundaries. Output column prefix [string] Prefix for output fields. Default: _ Load whole raster in memory [boolean] Determines if raster band will be loaded in memory (True) or readed by chunks (False). Useful only when disk IO or raster scanning inefficiencies are your limiting factor. Default: True Outputs Output layer [vector] The resulting layer. Basically this is same layer as zones layer with new columns containing statistics added. Console usage processing.runalg(’qgis:zonalstatistics’, input_raster, raster_band, input_vector, column_prefix, global_extent, output_layer) See also . 18.5.4 Table Frequency analysis Description 362 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters input [vector: any] fields [string] Default: (not set) Outputs output [table] Console usage processing.runalg(’qgis:frequencyanalysis’, input, fields, output) See also . 18.5.5 Vector analysis Count points in polygon Description Counts the number of points present in each feature of a polygon layer. Parameters Polygons [vector: polygon] Polygons layer. Points [vector: point] Points layer. Count field name [string] The name of the attribute table column containing the points number. Default: NUMPOINTS Outputs Result [vector] Resulting layer with the attribute table containing the new column of the points count. Console usage processing.runalg(’qgis:countpointsinpolygon’, polygons, points, field, output) 18.5. QGIS algorithm provider 363 QGIS User Guide, Release 2.6 See also Count points in polygon (weighted) Description Counts the number of points in each feature of a polygon layer and calculates the mean of the selected field for each feature of the polygon layer. These values will be added to the attribute table of the resulting polygon layer. Parameters Polygons [vector: polygon] Polygons layer. Points [vector: point] Points layer. Weight field [tablefield: any] Weight field of the points attribute table. Count field name [string] Name of the column for the new weighted field. Default: NUMPOINTS Outputs Result [vector] The resulting polygons layer. Console usage processing.runalg(’qgis:countpointsinpolygonweighted’, polygons, points, weight, field, output) See also Count unique points in polygon Description Counts the number of unique values of a points in a polygons layer. Creates a new polygons layer with an extra column in the attribute table containing the count of unique values for each feature. Parameters Polygons [vector: polygon] Polygons layer. Points [vector: point] Points layer. Class field [tablefield: any] Points layer column name of the unique value chosen. Count field name [string] Column name containing the count of unique values in the resulting polygons layer. Default: NUMPOINTS Outputs Result [vector] The resulting polygons layer. 364 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’qgis:countuniquepointsinpolygon’, polygons, points, classfield, field, output) See also Distance matrix Description Parameters Input point layer [vector: point] Input unique ID field [tablefield: any] Target point layer [vector: point] Target unique ID field [tablefield: any] Output matrix type [selection] Options: • 0 — Linear (N*k x 3) distance matrix • 1 — Standard (N x T) distance matrix • 2 — Summary distance matrix (mean, std. dev., min, max) Default: 0 Use only the nearest (k) target points [number] Default: 0 Outputs Distance matrix [table] Console usage processing.runalg(’qgis:distancematrix’, input_layer, input_field, target_layer, target_field, matrix_type, nearest_points, distance_matrix) See also Distance to nearest hub Description 18.5. QGIS algorithm provider 365 QGIS User Guide, Release 2.6 Parameters Source points layer [vector: any] Destination hubs layer [vector: any] Hub layer name attribute [tablefield: any] Output shape type [selection] Options: • 0 — Point • 1 — Line to hub Default: 0 Measurement unit [selection] Options: • 0 — Meters • 1 — Feet • 2 — Miles • 3 — Kilometers • 4 — Layer units Default: 0 Outputs Output [vector] Console usage processing.runalg(’qgis:distancetonearesthub’, points, hubs, field, geometry, unit, output) See also Generate points (pixel centroids) along line Description Parameters Raster layer [raster] Vector layer [vector: line] Outputs Output layer [vector] 366 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’qgis:generatepointspixelcentroidsalongline’, input_raster, input_vector, output_layer) See also Generate points (pixel centroids) inside polygons Description Parameters Raster layer [raster] Vector layer [vector: polygon] Outputs Output layer [vector] Console usage processing.runalg(’qgis:generatepointspixelcentroidsinsidepolygons’, input_raster, input_vector, output_layer) See also Hub lines Description Creates hub and spoke diagrams with lines drawn from points on the Spoke Point layer to matching points in the Hub Point layer. Determination of which hub goes with each point is based on a match between the Hub ID field on the hub points and the Spoke ID field on the spoke points. Parameters Hub point layer [vector: any] Hub ID field [tablefield: any] Spoke point layer [vector: any] Spoke ID field [tablefield: any] Outputs Output [vector] The resulting layer. 18.5. QGIS algorithm provider 367 QGIS User Guide, Release 2.6 Console usage processing.runalg(’qgis:hublines’, hubs, hub_field, spokes, spoke_field, output) See also Mean coordinate(s) Description Calculates the mean of the coordinates of a layer starting from a field of the attribute table. Parameters Input layer [vector: any] Weight field [tablefield: numeric] Optional. Field to use if you want to perform a weighted mean. Unique ID field [tablefield: numeric] Optional. Unique field on which the calculation of the mean will be made. Outputs Result [vector] The resulting points layer. Console usage processing.runalg(’qgis:meancoordinates’, points, weight, uid, output) See also Nearest neighbour analysis Description Parameters Points [vector: point] Outputs Result [html] Observed mean distance [number] Expected mean distance [number] Nearest neighbour index [number] 368 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Number of points [number] Z-Score [number] Console usage processing.runalg(’qgis:nearestneighbouranalysis’, points, output) See also Sum line lengths Description Parameters Lines [vector: line] Polygons [vector: polygon] Lines length field name [string] Default: LENGTH Lines count field name [string] Default: COUNT Outputs Result [vector] Console usage processing.runalg(’qgis:sumlinelengths’, lines, polygons, len_field, count_field, output) See also . 18.5.6 Vector creation Create grid Description Creates a grid. 18.5. QGIS algorithm provider 369 QGIS User Guide, Release 2.6 Parameters Grid type [selection] Grid type. Options: • 0 — Rectangle (line) • 1 — Rectangle (polygon) • 2 — Diamond (polygon) • 3 — Hexagon (polygon) Default: 0 Width [number] Horizontal extent of the grid. Default: 360.0 Height [number] Vertical extent of the grid. Default: 180.0 Horizontal spacing [number] X-axes spacing between the lines. Default: 10.0 Vertical spacing [number] Y-axes spacing between the lines. Default: 10.0 Center X [number] X-coordinate of the grid center. Default: 0.0 Center Y [number] Y-coordinate of the grid center. Default: 0.0 Output CRS [crs] Coordinate reference system for grid. Default: EPSG:4326 Outputs Output [vector] The resulting grid layer (lines or polygons). Console usage processing.runalg(’qgis:creategrid’, type, width, height, hspacing, vspacing, centerx, centery, crs, output) See also Points layer from table Description Creates points layer from geometryless table with columns that contain point coordinates. 370 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input layer [table] Input table X field [tablefield: any] Table column containing the X coordinate. Y field [tablefield: any] Table column containing the Y coordinate. Target CRS [crs] Coordinate reference system to use for layer. Default: EPSG:4326 Outputs Output layer [vector] The resulting layer. Console usage processing.runalg(’qgis:pointslayerfromtable’, input, xfield, yfield, target_crs, output) See also Points to path Description Parameters Input point layer [vector: point] Group field [tablefield: any] Order field [tablefield: any] Date format (if order field is DateTime) [string] Optional. Default: (not set) Outputs Paths [vector] Directory [directory] Console usage processing.runalg(’qgis:pointstopath’, vector, group_field, order_field, date_format, output_lines, output_text) 18.5. QGIS algorithm provider 371 QGIS User Guide, Release 2.6 See also Random points along line Description Parameters Input layer [vector: line] Number of points [number] Default: 1 Minimum distance [number] Default: 0.0 Outputs Random points [vector] Console usage processing.runalg(’qgis:randompointsalongline’, vector, point_number, min_distance, output) See also Random points in extent Description Parameters Input extent [extent] Default: 0,1,0,1 Points number [number] Default: 1 Minimum distance [number] Default: 0.0 Outputs Random points [vector] 372 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’qgis:randompointsinextent’, extent, point_number, min_distance, output) See also Random points in layer bounds Description Parameters Input layer [vector: polygon] Points number [number] Default: 1 Minimum distance [number] Default: 0.0 Outputs Random points [vector] Console usage processing.runalg(’qgis:randompointsinlayerbounds’, vector, point_number, min_distance, output) See also Random points inside polygons (fixed) Description Parameters Input layer [vector: polygon] Sampling strategy [selection] Options: • 0 — Points count • 1 — Points density Default: 0 18.5. QGIS algorithm provider 373 QGIS User Guide, Release 2.6 Number or density of points [number] Default: 1.0 Minimum distance [number] Default: 0.0 Outputs Random points [vector] Console usage processing.runalg(’qgis:randompointsinsidepolygonsfixed’, vector, strategy, value, min_distance, output) See also Random points inside polygons (variable) Description Parameters Input layer [vector: polygon] Sampling strategy [selection] Options: • 0 — Points count • 1 — Points density Default: 0 Number field [tablefield: numeric] Minimum distance [number] Default: 0.0 Outputs Random points [vector] Console usage processing.runalg(’qgis:randompointsinsidepolygonsvariable’, vector, strategy, field, min_distance, output) 374 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Regular points Description Parameters Input extent [extent] Default: 0,1,0,1 Point spacing/count [number] Default: 0.0001 Initial inset from corner (LH side) [number] Default: 0.0 Apply random offset to point spacing [boolean] Default: False Use point spacing [boolean] Default: True Outputs Regular points [vector] Console usage processing.runalg(’qgis:regularpoints’, extent, spacing, inset, randomize, is_spacing, output) See also Vector grid Description Parameters Grid extent [extent] Default: 0,1,0,1 X spacing [number] Default: 0.0001 Y spacing [number] Default: 0.0001 18.5. QGIS algorithm provider 375 QGIS User Guide, Release 2.6 Grid type [selection] Options: • 0 — Output grid as polygons • 1 — Output grid as lines Default: 0 Outputs Grid [vector] Console usage processing.runalg(’qgis:vectorgrid’, extent, step_x, step_y, type, output) See also . 18.5.7 Vector general Delete duplicate geometries Description Parameters Input layer [vector: any] Outputs Output [vector] Console usage processing.runalg(’qgis:deleteduplicategeometries’, input, output) See also Join atributes by location Description 376 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Target vector layer [vector: any] Join vector layer [vector: any] Attribute summary [selection] Options: • 0 — Take attributes of the first located feature • 1 — Take summary of intersecting features Default: 0 Statistics for summary (comma separated) [string] Default: sum,mean,min,max,median Output table [selection] Options: • 0 — Only keep matching records • 1 — Keep all records (including non-matching target records) Default: 0 Outputs Output layer [vector] Console usage processing.runalg(’qgis:joinatributesbylocation’, target, join, summary, stats, keep, output) See also Join attributes table Description Parameters Input layer [vector: any] Input layer 2 [table] Table field [tablefield: any] Table field 2 [tablefield: any] Outputs Output layer [vector] 18.5. QGIS algorithm provider 377 QGIS User Guide, Release 2.6 Console usage processing.runalg(’qgis:joinattributestable’, input_layer, input_layer_2, table_field, table_field_2, output_layer) See also Merge vector layers Description Parameters Input layer 1 [vector: any] Input layer 2 [vector: any] Outputs Output [vector] Console usage processing.runalg(’qgis:mergevectorlayers’, layer1, layer2, output) See also Polygon from layer extent Description Parameters Input layer [vector: any] Calculate extent for each feature separately [boolean] Default: False Outputs Output layer [vector] Console usage processing.runalg(’qgis:polygonfromlayerextent’, input_layer, by_feature, output) 378 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Reproject layer Description Reprojects a vector layer in a different CRS. Parameters Input layer [vector: any] Layer to reproject. Target CRS [crs] Destination coordinate reference system. Default: EPSG:4326 Outputs Reprojected layer [vector] The resulting layer. Console usage processing.runalg(’qgis:reprojectlayer’, input, target_crs, output) See also Save selected features Description Saves the selected features as a new layer. Parameters Input layer [vector: any] Layer to process. Outputs Output layer with selected features [vector] The resulting layer. Console usage processing.runalg(’qgis:saveselectedfeatures’, input_layer, output_layer) 18.5. QGIS algorithm provider 379 QGIS User Guide, Release 2.6 See also Set style for vector layer Description Parameters Vector layer [vector: any] Style file [file] Outputs Styled layer [vector] Console usage processing.runalg(’qgis:setstyleforvectorlayer’, input, style) See also Snap points to grid Description Parameters Input Layer [vector: any] Horizontal spacing [number] Default: 0.1 Vertical spacing [number] Default: 0.1 Outputs Output [vector] Console usage processing.runalg(’qgis:snappointstogrid’, input, hspacing, vspacing, output) 380 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Split vector layer Description Parameters Input layer [vector: any] Unique ID field [tablefield: any] Outputs Output directory [directory] Console usage processing.runalg(’qgis:splitvectorlayer’, input, field, output) See also . 18.5.8 Vector geometry Concave hull Description Parameters Input point layer [vector: point] Threshold (0-1, where 1 is equivalent with Convex Hull) [number] Default: 0.3 Allow holes [boolean] Default: True Split multipart geometry into singleparts geometries [boolean] Default: False 18.5. QGIS algorithm provider 381 QGIS User Guide, Release 2.6 Outputs Concave hull [vector] Console usage processing.runalg(’qgis:concavehull’, input, alpha, holes, no_multigeometry, output) See also Convert geometry type Description Converts a geometry type to another one. Parameters Input layer [vector: any] Layer in input. New geometry type [selection] Type of conversion to perform. Options: • 0 — Centroids • 1 — Nodes • 2 — Linestrings • 3 — Multilinestrings • 4 — Polygons Default: 0 Outputs Output [vector] The resulting layer. Console usage processing.runalg(’qgis:convertgeometrytype’, input, type, output) See also Convex hull Description 382 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input layer [vector: any] Field (optional, only used if creating convex hulls by classes) [tablefield: any] Optional. Method [selection] Options: • 0 — Create single minimum convex hull • 1 — Create convex hulls based on field Default: 0 Outputs Convex hull [vector] Console usage processing.runalg(’qgis:convexhull’, input, field, method, output) See also Create points along lines Description Parameters lines [vector: any] distance [number] Default: 1 startpoint [number] Default: 0 endpoint [number] Default: 0 Outputs output [vector] 18.5. QGIS algorithm provider 383 QGIS User Guide, Release 2.6 Console usage processing.runalg(’qgis:createpointsalonglines’, lines, distance, startpoint, endpoint, output) See also Delaunay triangulation Description Parameters Input layer [vector: point] Outputs Delaunay triangulation [vector] Console usage processing.runalg(’qgis:delaunaytriangulation’, input, output) See also Densify geometries given an interval Description Parameters Input layer [vector: polygon, line] Interval between Vertices to add [number] Default: 1.0 Outputs Densified layer [vector] Console usage processing.runalg(’qgis:densifygeometriesgivenaninterval’, input, interval, output) 384 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Densify geometries Description Parameters Input layer [vector: polygon, line] Vertices to add [number] Default: 1 Outputs Densified layer [vector] Console usage processing.runalg(’qgis:densifygeometries’, input, vertices, output) See also Dissolve Description Parameters Input layer [vector: polygon, line] Dissolve all (do not use field) [boolean] Default: True Unique ID field [tablefield: any] Optional. Outputs Dissolved [vector] Console usage processing.runalg(’qgis:dissolve’, input, dissolve_all, field, output) 18.5. QGIS algorithm provider 385 QGIS User Guide, Release 2.6 See also Eliminate sliver polygons Description Parameters Input layer [vector: polygon] Use current selection in input layer (works only if called from toolbox) [boolean] Default: False Selection attribute [tablefield: any] Comparison [selection] Options: • 0 — == • 1 — != •2—> • 3 — >= •4—< • 5 — <= • 6 — begins with • 7 — contains Default: 0 Value [string] Default: 0 Merge selection with the neighbouring polygon with the [selection] Options: • 0 — Largest area • 1 — Smallest Area • 2 — Largest common boundary Default: 0 Outputs Cleaned layer [vector] 386 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’qgis:eliminatesliverpolygons’, input, keepselection, attribute, comparison, comparisonvalue, mode, output) See also Explode lines Description Parameters Input layer [vector: line] Outputs Output layer [vector] Console usage processing.runalg(’qgis:explodelines’, input, output) See also Extract nodes Description Parameters Input layer [vector: polygon, line] Outputs Output layer [vector] Console usage processing.runalg(’qgis:extractnodes’, input, output) 18.5. QGIS algorithm provider 387 QGIS User Guide, Release 2.6 See also Fill holes Description Parameters Polygons [vector: any] Max area [number] Default: 100000 Outputs Results [vector] Console usage processing.runalg(’qgis:fillholes’, polygons, max_area, results) See also Fixed distance buffer Description Parameters Input layer [vector: any] Distance [number] Default: 10.0 Segments [number] Default: 5 Dissolve result [boolean] Default: False Outputs Buffer [vector] 388 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’qgis:fixeddistancebuffer’, input, distance, segments, dissolve, output) See also Keep n biggest parts Description Parameters Polygons [vector: polygon] To keep [number] Default: 1 Outputs Results [vector] Console usage processing.runalg(’qgis:keepnbiggestparts’, polygons, to_keep, results) See also Lines to polygons Description Parameters Input layer [vector: line] Outputs Output layer [vector] Console usage processing.runalg(’qgis:linestopolygons’, input, output) 18.5. QGIS algorithm provider 389 QGIS User Guide, Release 2.6 See also Multipart to singleparts Description Parameters Input layer [vector: any] Outputs Output layer [vector] Console usage processing.runalg(’qgis:multiparttosingleparts’, input, output) See also Points displacement Description Moves overlapped points at small distance, that they all become visible. The result is very similar to the output of the “Point displacement” renderer but it is permanent. Parameters Input layer [vector: point] Layer with overlapped points. Displacement distance [number] Desired displacement distance NOTE: displacement distance should be in same units as layer. Default: 0.00015 Horizontal distribution for two point case [boolean] Controls distrobution direction in case of two overlapped points. If True points wwill be distributed horizontally, otherwise they will be distributed vertically. Default: True Outputs Output layer [vector] The resulting layer with shifted overlapped points. Console usage processing.runalg(’qgis:pointsdisplacement’, input_layer, distance, horizontal, output_layer) 390 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Polygon centroids Description Parameters Input layer [vector: polygon] Outputs Output layer [vector] Console usage processing.runalg(’qgis:polygoncentroids’, input_layer, output_layer) See also Polygonize Description Parameters Input layer [vector: line] Keep table structure of line layer [boolean] Default: False Create geometry columns [boolean] Default: True Outputs Output layer [vector] Console usage processing.runalg(’qgis:polygonize’, input, fields, geometry, output) 18.5. QGIS algorithm provider 391 QGIS User Guide, Release 2.6 See also Polygons to lines Description Parameters Input layer [vector: polygon] Outputs Output layer [vector] Console usage processing.runalg(’qgis:polygonstolines’, input, output) See also Simplify geometries Description Parameters Input layer [vector: polygon, line] Tolerance [number] Default: 1.0 Outputs Simplified layer [vector] Console usage processing.runalg(’qgis:simplifygeometries’, input, tolerance, output) 392 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Singleparts to multipart Description Parameters Input layer [vector: any] Unique ID field [tablefield: any] Outputs Output layer [vector] Console usage processing.runalg(’qgis:singlepartstomultipart’, input, field, output) See also Variable distance buffer Description Parameters Input layer [vector: any] Distance field [tablefield: any] Segments [number] Default: 5 Dissolve result [boolean] Default: False Outputs Buffer [vector] Console usage processing.runalg(’qgis:variabledistancebuffer’, input, field, segments, dissolve, output) 18.5. QGIS algorithm provider 393 QGIS User Guide, Release 2.6 See also Voronoi polygons Description Parameters Input layer [vector: point] Buffer region [number] Default: 0.0 Outputs Voronoi polygons [vector] Console usage processing.runalg(’qgis:voronoipolygons’, input, buffer, output) See also . 18.5.9 Vector overlay Clip Description Parameters Input layer [vector: any] Clip layer [vector: any] Outputs Clipped [vector] Console usage processing.runalg(’qgis:clip’, input, overlay, output) 394 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Difference Description Parameters Input layer [vector: any] Difference layer [vector: any] Outputs Difference [vector] Console usage processing.runalg(’qgis:difference’, input, overlay, output) See also Intersection Description Parameters Input layer [vector: any] Intersect layer [vector: any] Outputs Intersection [vector] Console usage processing.runalg(’qgis:intersection’, input, input2, output) 18.5. QGIS algorithm provider 395 QGIS User Guide, Release 2.6 See also Line intersections Description Parameters Input layer [vector: line] Intersect layer [vector: line] Input unique ID field [tablefield: any] Intersect unique ID field [tablefield: any] Outputs Output layer [vector] Console usage processing.runalg(’qgis:lineintersections’, input_a, input_b, field_a, field_b, output) See also Symetrical difference Description Parameters Input layer [vector: any] Difference layer [vector: any] Outputs Symetrical difference [vector] Console usage processing.runalg(’qgis:symetricaldifference’, input, overlay, output) 396 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Union Description Parameters Input layer [vector: any] Input layer 2 [vector: any] Outputs Union [vector] Console usage processing.runalg(’qgis:union’, input, input2, output) See also . 18.5.10 Vector selection Extract by attribute Description Parameters Input Layer [vector: any] Selection attribute [tablefield: any] Operator [selection] Options: •0—= • 1 — != •2—> • 3 — >= •4—< • 5 — <= • 6 — begins with 18.5. QGIS algorithm provider 397 QGIS User Guide, Release 2.6 • 7 — contains Default: 0 Value [string] Default: (not set) Outputs Output [vector] Console usage processing.runalg(’qgis:extractbyattribute’, input, field, operator, value, output) See also Extract by location Description Parameters Layer to select from [vector: any] Additional layer (intersection layer) [vector: any] Include input features that touch the selection features [boolean] Default: False Include input features that overlap/cross the selection features [boolean] Default: False Include input features completely within the selection features [boolean] Default: False Outputs Selection [vector] Console usage processing.runalg(’qgis:extractbylocation’, input, intersect, touches, overlaps, within, output) 398 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Random extract Description Parameters Input layer [vector: any] Method [selection] Options: • 0 — Number of selected features • 1 — Percentage of selected features Default: 0 Number/percentage of selected features [number] Default: 10 Outputs Selection [vector] Console usage processing.runalg(’qgis:randomextract’, input, method, number, output) See also Random extract within subsets Description Parameters Input layer [vector: any] ID Field [tablefield: any] Method [selection] Options: • 0 — Number of selected features • 1 — Percentage of selected features Default: 0 18.5. QGIS algorithm provider 399 QGIS User Guide, Release 2.6 Number/percentage of selected features [number] Default: 10 Outputs Selection [vector] Console usage processing.runalg(’qgis:randomextractwithinsubsets’, input, field, method, number, output) See also Random selection Description Parameters Input layer [vector: any] Method [selection] Options: • 0 — Number of selected features • 1 — Percentage of selected features Default: 0 Number/percentage of selected features [number] Default: 10 Outputs Selection [vector] Console usage processing.runalg(’qgis:randomselection’, input, method, number) See also Random selection within subsets Description 400 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input layer [vector: any] ID Field [tablefield: any] Method [selection] Options: • 0 — Number of selected features • 1 — Percentage of selected features Default: 0 Number/percentage of selected features [number] Default: 10 Outputs Selection [vector] Console usage processing.runalg(’qgis:randomselectionwithinsubsets’, input, field, method, number) See also Select by attribute Description Selects and saves as new layer all features from input layer that satisfy condition. NOTE: algorithm is case-sensitive (“qgis” is different from “Qgis” and “QGIS”) Parameters Input Layer [vector: any] Layer to process. Selection attribute [tablefield: any] Field on which perform the selection. Operator [selection] Comparison operator. Options: •0—= • 1 — != •2—> • 3 — >= •4—< • 5 — <= • 6 — begins with • 7 — contains 18.5. QGIS algorithm provider 401 QGIS User Guide, Release 2.6 Default: 0 Value [string] Value to compare. Default: (not set) Outputs Output [vector] The resulting layer. Console usage processing.runalg(’qgis:selectbyattribute’, input, field, operator, value, output) See also Select by expression Description Parameters Input Layer [vector: any] Expression [string] Default: (not set) Modify current selection by [selection] Options: • 0 — creating new selection • 1 — adding to current selection • 2 — removing from current selection Default: 0 Outputs Output [vector] Console usage processing.runalg(’qgis:selectbyexpression’, layername, expression, method) 402 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Select by location Description Parameters Layer to select from [vector: any] Additional layer (intersection layer) [vector: any] Include input features that touch the selection features [boolean] Default: False Include input features that overlap/cross the selection features [boolean] Default: False Include input features completely within the selection features [boolean] Default: False Modify current selection by [selection] Options: • 0 — creating new selection • 1 — adding to current selection • 2 — removing from current selection Default: 0 Outputs Selection [vector] Console usage processing.runalg(’qgis:selectbylocation’, input, intersect, touches, overlaps, within, method) See also . 18.5. QGIS algorithm provider 403 QGIS User Guide, Release 2.6 18.5.11 Vector table Add autoincremental field Description Parameters Input layer [vector: any] Outputs Output layer [vector] Console usage processing.runalg(’qgis:addautoincrementalfield’, input, output) See also Add field to attributes table Description Parameters Input layer [vector: any] Field name [string] Default: (not set) Field type [selection] Options: • 0 — Integer • 1 — Float • 2 — String Default: 0 Field length [number] Default: 10 Field precision [number] Default: 0 404 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Output layer [vector] Console usage processing.runalg(’qgis:addfieldtoattributestable’, input_layer, field_name, field_type, field_length, field_precision, output_layer) See also Advanced Python field calculator Description Parameters Input layer [vector: any] Result field name [string] Default: NewField Field type [selection] Options: • 0 — Integer • 1 — Float • 2 — String Default: 0 Field length [number] Default: 10 Field precision [number] Default: 0 Global expression [string] Optional. Default: (not set) Formula [string] Default: value = Outputs Output layer [vector] 18.5. QGIS algorithm provider 405 QGIS User Guide, Release 2.6 Console usage processing.runalg(’qgis:advancedpythonfieldcalculator’, input_layer, field_name, field_type, field_length, field_precision, global, formula, output_layer) See also Basic statistics for numeric fields Description Parameters Input vector layer [vector: any] Field to calculate statistics on [tablefield: numeric] Outputs Statistics for numeric field [html] Coefficient of Variation [number] Minimum value [number] Maximum value [number] Sum [number] Mean value [number] Count [number] Range [number] Median [number] Number of unique values [number] Standard deviation [number] Console usage processing.runalg(’qgis:basicstatisticsfornumericfields’, input_layer, field_name, output_html_file) See also Basic statistics for text fields Description 406 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input vector layer [vector: any] Field to calculate statistics on [tablefield: string] Outputs Statistics for text field [html] Minimum length [number] Maximum length [number] Mean length [number] Count [number] Number of empty values [number] Number of non-empty values [number] Number of unique values [number] Console usage processing.runalg(’qgis:basicstatisticsfortextfields’, input_layer, field_name, output_html_file) See also Create equivalent numerical field Description Parameters Input layer [vector: any] Class field [tablefield: any] Outputs Output layer [vector] Console usage processing.runalg(’qgis:createequivalentnumericalfield’, input, field, output) 18.5. QGIS algorithm provider 407 QGIS User Guide, Release 2.6 See also Delete column Description Parameters Input layer [vector: any] Field to delete [tablefield: any] Outputs Output [vector] Console usage processing.runalg(’qgis:deletecolumn’, input, column, output) See also Export/Add geometry columns Description Parameters Input layer [vector: any] Calculate using [selection] Options: • 0 — Layer CRS • 1 — Project CRS • 2 — Ellipsoidal Default: 0 Outputs Output layer [vector] Console usage 408 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 processing.runalg(’qgis:exportaddgeometrycolumns’, input, calc_method, output) See also Field calculator Description Parameters Input layer [vector: any] Result field name [string] Default: (not set) Field type [selection] Options: • 0 — Float • 1 — Integer • 2 — String • 3 — Date Default: 0 Field length [number] Default: 10 Field precision [number] Default: 3 Create new field [boolean] Default: True Formula [string] Default: (not set) Outputs Output layer [vector] Console usage processing.runalg(’qgis:fieldcalculator’, input_layer, field_name, field_type, field_length, field_precision, new_field, formula, output_layer) 18.5. QGIS algorithm provider 409 QGIS User Guide, Release 2.6 See also List unique values Description Lists unique values of an attribute table field and counts their number. Parameters Input layer [vector: any] Layer to analyze. Target field [tablefield: any] Field to analyze. Outputs Unique values [html] Analysis results in HTML format. Total unique values [number] Total number of unique values in given field. Unique values [string] List of all unique values in given field. Console usage processing.runalg(’qgis:listuniquevalues’, input_layer, field_name, output) See also Number of unique values in classes Description Parameters input [vector: any] class field [tablefield: any] value field [tablefield: any] Outputs output [vector] Console usage processing.runalg(’qgis:numberofuniquevaluesinclasses’, input, class_field, value_field, output) 410 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Statistics by categories Description Parameters Input vector layer [vector: any] Field to calculate statistics on [tablefield: numeric] Field with categories [tablefield: any] Outputs Statistics [table] Console usage processing.runalg(’qgis:statisticsbycategories’, input_layer, values_field_name, categories_field_name, output) See also Text to float Description Parameters Input Layer [vector: any] Text attribute to convert to float [tablefield: string] Outputs Output [vector] Console usage processing.runalg(’qgis:texttofloat’, input, field, output) See also . 18.5. QGIS algorithm provider 411 QGIS User Guide, Release 2.6 18.6 R algorithm provider R also called GNU S, is a strongly functional language and environment to statistically explore data sets, make many graphical displays of data from custom data sets Note: Please remember that Processing contains only R scripts, so you need to install R by yourself and configure Processing properly. . 18.6.1 Basic statistics Frequency table Description Parameters Layer [vector: any] Field [tablefield: any] Outputs R Console Output [html] Console usage processing.runalg(’r:frequencytable’, layer, field, r_console_output) See also Kolmogrov-Smirnov test Description Parameters Layer [vector: any] Field [tablefield: any] Outputs R Console Output [html] 412 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’r:kolmogrovsmirnovtest’, layer, field, r_console_output) See also Summary statistics Description Parameters Layer [vector: any] Field [tablefield: any] Outputs R Console Output [html] Console usage processing.runalg(’r:summarystatistics’, layer, field, r_console_output) See also . 18.6.2 Home range Characteristic hull method Description Parameters Layer [vector: any] Field [tablefield: any] Outputs Home_ranges [vector] 18.6. R algorithm provider 413 QGIS User Guide, Release 2.6 Console usage processing.runalg(’r:characteristichullmethod’, layer, field, home_ranges) See also Kernel h ref Description Parameters Layer [vector: any] Field [tablefield: any] Grid [number] Default: 10.0 Percentage [number] Default: 10.0 Folder [directory] Optional. Outputs Home_ranges [vector] Console usage processing.runalg(’r:kernelhref’, layer, field, grid, percentage, folder, home_ranges) See also Minimum convex polygon Description Parameters Layer [vector: any] Percentage [number] Default: 10.0 Field [tablefield: any] 414 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Home_ranges [vector] Console usage processing.runalg(’r:minimumconvexpolygon’, layer, percentage, field, home_ranges) See also Single-linkage cluster analysis Description Parameters Layer [vector: any] Field [tablefield: any] Percentage [number] Default: 10.0 Outputs R Plots [html] Home_ranges [vector] Console usage processing.runalg(’r:singlelinkageclusteranalysis’, layer, field, percentage, rplots, home_ranges) See also . 18.6.3 Point pattern F function Description 18.6. R algorithm provider 415 QGIS User Guide, Release 2.6 Parameters Layer [vector: any] Nsim [number] Default: 10.0 Outputs R Plots [html] Console usage processing.runalg(’r:ffunction’, layer, nsim, rplots) See also G function Description Parameters Layer [vector: any] Nsim [number] Default: 10.0 Outputs R Plots [html] Console usage processing.runalg(’r:gfunction’, layer, nsim, rplots) See also Monte-Carlo spatial randomness Description 416 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Layer [vector: any] Simulations [number] Default: 100.0 Optional plot name [string] Default: (not set) Outputs R Plots [html] R Console Output [html] Console usage processing.runalg(’r:montecarlospatialrandomness’, layer, simulations, optional_plot_name, rplots, r_console_output) See also Quadrat analysis Description Parameters Layer [vector: any] Outputs R Plots [html] R Console Output [html] Console usage processing.runalg(’r:quadratanalysis’, layer, rplots, r_console_output) See also Random sampling grid Description 18.6. R algorithm provider 417 QGIS User Guide, Release 2.6 Parameters Layer [vector: any] Size [number] Default: 10.0 Outputs Output [vector] Console usage processing.runalg(’r:randomsamplinggrid’, layer, size, output) See also Regular sampling grid Description Parameters Layer [vector: any] Size [number] Default: 10.0 Outputs Output [vector] Console usage processing.runalg(’r:regularsamplinggrid’, layer, size, output) See also Relative distribution (distance covariate) Description 418 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Layer [vector: any] Covariate [vector: any] Covariate name [string] Default: mandatory_covariate_name_(no_spaces) x label [string] Default: (not set) Plot name [string] Default: (not set) Legend position [string] Default: float Outputs R Plots [html] Console usage processing.runalg(’r:relativedistributiondistancecovariate’, layer, covariate, covariate_name, x_label, plot_name, legend_position, rplots) See also Relative distribution (raster covariate) Description Parameters points [vector: any] covariate [raster] covariate name [string] Default: mandatory_covariate_name_(no_spaces) x label [string] Default: (not set) plot name [string] Default: (not set) legend position [string] Default: float 18.6. R algorithm provider 419 QGIS User Guide, Release 2.6 Outputs R Plots [html] Console usage processing.runalg(’r:relativedistributionrastercovariate’, points, covariate, covariate_name, x_label, plot_name, legend_position, rplots) See also Ripley - Rasson spatial domain Description Parameters Layer [vector: any] Outputs Output [vector] Console usage processing.runalg(’r:ripleyrassonspatialdomain’, layer, output) See also . 18.6.4 Raster processing Advanced raster histogram Description Parameters Layer [raster] Dens or Hist [string] Default: Hist 420 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs R Plots [html] Console usage processing.runalg(’r:advancedrasterhistogram’, layer, dens_or_hist, rplots) See also Raster histogram Description Parameters Layer [raster] Outputs R Plots [html] Console usage processing.runalg(’r:rasterhistogram’, layer, rplots) See also . 18.6.5 Vector processing Histogram Description Parameters Layer [vector: any] Field [tablefield: any] Outputs R Plots [html] 18.6. R algorithm provider 421 QGIS User Guide, Release 2.6 Console usage processing.runalg(’r:histogram’, layer, field, rplots) See also . 18.7 SAGA algorithm provider SAGA (System for Automated Geoscientific Analyses) is a free, hybrid, cross-platform GIS software. SAGA provides many geoscientific methods which are bundled in so-called module libraries. Note: Please remember that Processing contains only the interface description, so you need to install SAGA by yourself and configure Processing properly. . 18.7.1 Geostatistics Directional statistics for single grid Description Parameters Grid [raster] Points [vector: any] Optional. Direction [Degree] [number] Default: 0.0 Tolerance [Degree] [number] Default: 0.0 Maximum Distance [Cells] [number] Default: 0 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 422 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1.0 Outputs Arithmetic Mean [raster] Difference from Arithmetic Mean [raster] Minimum [raster] Maximum [raster] Range [raster] Variance [raster] Standard Deviation [raster] Mean less Standard Deviation [raster] Mean plus Standard Deviation [raster] Deviation from Arithmetic Mean [raster] Percentile [raster] Directional Statistics for Points [vector] Console usage processing.runalg(’saga:directionalstatisticsforsinglegrid’, grid, points, direction, tolerance, maxdistance, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, mean, difmean, min, max, range, var, stddev, stddevlo, stddevhi, devmean, percent, points_out) See also Fast representativeness Description Parameters Input [raster] Level of Generalisation [number] Default: 16 18.7. SAGA algorithm provider 423 QGIS User Guide, Release 2.6 Outputs Output [raster] Output Lod [raster] Output Seeds [raster] Console usage processing.runalg(’saga:fastrepresentativeness’, input, lod, result, result_lod, seeds) See also Geographically weighted multiple regression (points/grids) Description Parameters Predictors [multipleinput: rasters] Output of Regression Parameters [boolean] Default: True Points [vector: point] Dependent Variable [tablefield: any] Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1.0 Search Range [selection] Options: • 0 — [0] search radius (local) • 1 — [1] no search radius (global) 424 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Default: 0 Search Radius [number] Default: 100 Search Mode [selection] Options: • 0 — [0] all directions • 1 — [1] quadrants Default: 0 Number of Points [selection] Options: • 0 — [0] maximum number of observations • 1 — [1] all points Default: 0 Maximum Number of Observations [number] Default: 10 Minimum Number of Observations [number] Default: 4 Outputs Regression [raster] Coefficient of Determination [raster] Regression Parameters [raster] Residuals [vector] Console usage processing.runalg(’saga:geographicallyweightedmultipleregressionpointsgrids’, predictors, parameters, points, dependent, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, range, radius, mode, npoints, maxpoints, minpoints, regression, quality, slopes, residuals) See also Geographically weighted multiple regression (points) Description Parameters Points [vector: any] Dependent Variable [tablefield: any] Distance Weighting [selection] Options: 18.7. SAGA algorithm provider 425 QGIS User Guide, Release 2.6 • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1.0 Search Range [selection] Options: • 0 — [0] search radius (local) • 1 — [1] no search radius (global) Default: 0 Search Radius [number] Default: 100 Search Mode [selection] Options: • 0 — [0] all directions • 1 — [1] quadrants Default: 0 Number of Points [selection] Options: • 0 — [0] maximum number of observations • 1 — [1] all points Default: 0 Maximum Number of Observations [number] Default: 10 Minimum Number of Observations [number] Default: 4 Outputs Regression [vector] 426 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:geographicallyweightedmultipleregressionpoints’, points, dependent, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, range, radius, mode, npoints, maxpoints, minpoints, regression) See also Geographically weighted multiple regression Description Parameters Points [vector: point] Dependent Variable [tablefield: any] Target Grids [selection] Options: • 0 — [0] user defined Default: 0 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1 Search Range [selection] Options: • 0 — [0] search radius (local) • 1 — [1] no search radius (global) Default: 0 Search Radius [number] Default: 100 Search Mode [selection] Options: 18.7. SAGA algorithm provider 427 QGIS User Guide, Release 2.6 • 0 — [0] all directions • 1 — [1] quadrants Default: 0 Number of Points [selection] Options: • 0 — [0] maximum number of observations • 1 — [1] all points Default: 0 Maximum Number of Observations [number] Default: 10 Minimum Number of Observations [number] Default: 4 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Quality [raster] Intercept [raster] Quality [raster] Intercept [raster] Console usage processing.runalg(’saga:geographicallyweightedmultipleregression’, points, dependent, target, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, range, radius, mode, npoints, maxpoints, minpoints, output_extent, user_size, user_quality, user_intercept, grid_quality, grid_intercept) See also Geographically weighted regression (points/grid) Description Parameters Predictor [raster] Points [vector: point] Dependent Variable [tablefield: any] Distance Weighting [selection] Options: 428 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1.0 Search Range [selection] Options: • 0 — [0] search radius (local) • 1 — [1] no search radius (global) Default: 0 Search Radius [number] Default: 0 Search Mode [selection] Options: • 0 — [0] all directions • 1 — [1] quadrants Default: 0 Number of Points [selection] Options: • 0 — [0] maximum number of observations • 1 — [1] all points Default: 0 Maximum Number of Observations [number] Default: 10 Minimum Number of Observations [number] Default: 4 Outputs Regression [raster] Coefficient of Determination [raster] Intercept [raster] Slope [raster] Residuals [vector] 18.7. SAGA algorithm provider 429 QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:geographicallyweightedregressionpointsgrid’, predictor, points, dependent, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, range, radius, mode, npoints, maxpoints, minpoints, regression, quality, intercept, slope, residuals) See also Geographically weighted regression Description Parameters Points [vector: point] Dependent Variable [tablefield: any] Predictor [tablefield: any] Target Grids [selection] Options: • 0 — [0] user defined Default: 0 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 0 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 0.0 Search Range [selection] Options: • 0 — [0] search radius (local) • 1 — [1] no search radius (global) Default: 0 Search Radius [number] Default: 100 430 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Search Mode [selection] Options: • 0 — [0] all directions • 1 — [1] quadrants Default: 0 Number of Points [selection] Options: • 0 — [0] maximum number of observations • 1 — [1] all points Default: 0 Maximum Number of Observations [number] Default: 10 Minimum Number of Observations [number] Default: 4 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Quality [raster] Intercept [raster] Slope [raster] Console usage processing.runalg(’saga:geographicallyweightedregression’, points, dependent, predictor, target, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, range, radius, mode, npoints, maxpoints, minpoints, output_extent, user_size, user_grid, user_quality, user_intercept, user_slope) See also Global moran’s i for grids Description Parameters Grid [raster] Case of contiguity [selection] Options: 18.7. SAGA algorithm provider 431 QGIS User Guide, Release 2.6 • 0 — [0] Rook • 1 — [1] Queen Default: 0 Outputs Result [table] Console usage processing.runalg(’saga:globalmoransiforgrids’, grid, contiguity, result) See also Minimum distance analysis Description Performs a complete distance analysis of a point layer: • minimum distance of points • maximum distance of points • average distance of all the points • standard deviation of the distance • duplicated points Parameters Points [vector: point] Layer to analyze. Outputs Minimum Distance Analysis [table] The resulting table. Console usage processing.runalg(’saga:minimumdistanceanalysis’, points, table) See also Multi-band variation Description 432 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Grids [multipleinput: rasters] Radius [Cells] [number] Default: 1 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1.0 Outputs Mean Distance [raster] Standard Deviation [raster] Distance [raster] Console usage processing.runalg(’saga:multibandvariation’, bands, radius, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, mean, stddev, diff) See also Multiple regression analysis (grid/grids) Description Parameters Dependent [raster] Grids [multipleinput: rasters] Grid Interpolation [selection] Options: 18.7. SAGA algorithm provider 433 QGIS User Guide, Release 2.6 • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 Include X Coordinate [boolean] Default: True Include Y Coordinate [boolean] Default: True Method [selection] Options: • 0 — [0] include all • 1 — [1] forward • 2 — [2] backward • 3 — [3] stepwise Default: 0 P in [number] Default: 5 P out [number] Default: 5 Outputs Regression [raster] Residuals [raster] Details: Coefficients [table] Details: Model [table] Details: Steps [table] Console usage processing.runalg(’saga:multipleregressionanalysisgridgrids’, dependent, grids, interpol, coord_x, coord_y, method, p_in, p_out, regression, residuals, info_coeff, info_model, info_steps) See also Multiple regression analysis (points/grids) Description 434 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Grids [multipleinput: rasters] Shapes [vector: any] Attribute [tablefield: any] Grid Interpolation [selection] Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 Include X Coordinate [boolean] Default: True Include Y Coordinate [boolean] Default: True Method [selection] Options: • 0 — [0] include all • 1 — [1] forward • 2 — [2] backward • 3 — [3] stepwise Default: 0 P in [number] Default: 5 P out [number] Default: 5 Outputs Details: Coefficients [table] Details: Model [table] Details: Steps [table] Residuals [vector] Regression [raster] Console usage processing.runalg(’saga:multipleregressionanalysispointsgrids’, grids, shapes, attribute, interpol, coord_x, coord_y, method, p_in, p_out, info_coeff, info_model, info_steps, residuals, regression) 18.7. SAGA algorithm provider 435 QGIS User Guide, Release 2.6 See also Polynomial regression Description Parameters Points [vector: any] Attribute [tablefield: any] Polynom [selection] Options: • 0 — [0] simple planar surface • 1 — [1] bi-linear saddle • 2 — [2] quadratic surface • 3 — [3] cubic surface • 4 — [4] user defined Default: 0 Maximum X Order [number] Default: 4 Maximum Y Order [number] Default: 4 Maximum Total Order [number] Default: 4 Trend Surface [selection] Options: • 0 — [0] user defined Default: 0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Residuals [vector] Grid [raster] 436 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:polynomialregression’, points, attribute, polynom, xorder, yorder, torder, target, output_extent, user_size, residuals, user_grid) See also Radius of variance (grid) Description Parameters Grid [raster] Standard Deviation [number] Default: 1.0 Maximum Search Radius (cells) [number] Default: 20 Type of Output [selection] Options: • 0 — [0] Cells • 1 — [1] Map Units Default: 0 Outputs Variance Radius [raster] Console usage processing.runalg(’saga:radiusofvariancegrid’, input, variance, radius, output, result) See also Regression analysis Description 18.7. SAGA algorithm provider 437 QGIS User Guide, Release 2.6 Parameters Grid [raster] Shapes [vector: any] Attribute [tablefield: any] Grid Interpolation [selection] Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 Regression Function [selection] Options: • 0 — [0] Y = a + b * X (linear) • 1 — [1] Y = a + b / X • 2 — [2] Y = a / (b - X) • 3 — [3] Y = a * X^b (power) • 4 — [4] Y = a e^(b * X) (exponential) • 5 — [5] Y = a + b * ln(X) (logarithmic) Default: 0 Outputs Regression [raster] Residuals [vector] Console usage processing.runalg(’saga:regressionanalysis’, grid, shapes, attribute, interpol, method, regression, residual) See also Representativeness Description 438 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Grid [raster] Radius (Cells) [number] Default: 10 Exponent [number] Default: 1 Outputs Representativeness [raster] Console usage processing.runalg(’saga:representativeness’, input, radius, exponent, result) See also Residual analysis Description Parameters Grid [raster] Radius (Cells) [number] Default: 7 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1.0 18.7. SAGA algorithm provider 439 QGIS User Guide, Release 2.6 Outputs Mean Value [raster] Difference from Mean Value [raster] Standard Deviation [raster] Value Range [raster] Minimum Value [raster] Maximum Value [raster] Deviation from Mean Value [raster] Percentile [raster] Console usage processing.runalg(’saga:residualanalysis’, grid, radius, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, mean, diff, stddev, range, min, max, devmean, percent) See also Spatial point pattern analysis Description Parameters Points [vector: point] Vertex Distance [Degree] [number] Default: 5 Outputs Mean Centre [vector] Standard Distance [vector] Bounding Box [vector] Console usage processing.runalg(’saga:spatialpointpatternanalysis’, points, step, centre, stddist, bbox) See also Statistics for grids Description 440 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Grids [multipleinput: rasters] Outputs Arithmetic Mean [raster] Minimum [raster] Maximum [raster] Variance [raster] Standard Deviation [raster] Mean less Standard Deviation [raster] Mean plus Standard Deviation [raster] Console usage processing.runalg(’saga:statisticsforgrids’, grids, mean, min, max, var, stddev, stddevlo, stddevhi) See also Variogram cloud Description Parameters Points [vector: point] Attribute [tablefield: any] Maximum Distance [number] Default: 0.0 Skip Number [number] Default: 1 Outputs Variogram Cloud [table] Console usage processing.runalg(’saga:variogramcloud’, points, field, distmax, nskip, result) 18.7. SAGA algorithm provider 441 QGIS User Guide, Release 2.6 See also Variogram surface Description Parameters Points [vector: point] Attribute [tablefield: any] Number of Distance Classes [number] Default: 10 Skip Number [number] Default: 1 Outputs Number of Pairs [raster] Variogram Surface [raster] Covariance Surface [raster] Console usage processing.runalg(’saga:variogramsurface’, points, field, distcount, nskip, count, variance, covariance) See also Zonal grid statistics Description Parameters Zone Grid [raster] Categorial Grids [multipleinput: rasters] Optional. Grids to analyse [multipleinput: rasters] Optional. Aspect [raster] Optional. 442 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Short Field Names [boolean] Default: True Outputs Zonal Statistics [table] Console usage processing.runalg(’saga:zonalgridstatistics’, zones, catlist, statlist, aspect, shortnames, outtab) See also . 18.7.2 Grid analysis Accumulated cost (anisotropic) Description Parameters Cost Grid [raster] Direction of max cost [raster] Destination Points [raster] k factor [number] Default: 1 Threshold for different route [number] Default: 0 Outputs Accumulated Cost [raster] Console usage processing.runalg(’saga:accumulatedcostanisotropic’, cost, direction, points, k, threshold, acccost) 18.7. SAGA algorithm provider 443 QGIS User Guide, Release 2.6 See also Accumulated cost (isotropic) Description Parameters Cost Grid [raster] Destination Points [raster] Threshold for different route [number] Default: 0.0 Outputs Accumulated Cost [raster] Closest Point [raster] Console usage processing.runalg(’saga:accumulatedcostisotropic’, cost, points, threshold, acccost, closestpt) See also Aggregation index Description Parameters Input Grid [raster] Max. Number of Classes [number] Default: 5 Outputs Result [table] Console usage processing.runalg(’saga:aggregationindex’, input, maxnumclass, result) 444 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Analytical hierarchy process Description Parameters Input Grids [multipleinput: rasters] Pairwise Comparisons Table [table] Outputs Output Grid [raster] Console usage processing.runalg(’saga:analyticalhierarchyprocess’, grids, table, output) See also Cross-classification and tabulation Description Parameters Input Grid 1 [raster] Input Grid 2 [raster] Max. Number of Classes [number] Default: 5 Outputs Cross-Classification Grid [raster] Cross-Tabulation Table [table] Console usage processing.runalg(’saga:crossclassificationandtabulation’, input, input2, maxnumclass, resultgrid, resulttable) 18.7. SAGA algorithm provider 445 QGIS User Guide, Release 2.6 See also Fragmentation (alternative) Description Parameters Classification [raster] Class Identifier [number] Default: 1 Neighborhood Min [number] Default: 1 Neighborhood Max [number] Default: 1 Level Aggregation [selection] Options: • 0 — [0] average • 1 — [1] multiplicative Default: 0 Add Border [boolean] Default: True Connectivity Weighting [number] Default: 1.1 Minimum Density [Percent] [number] Default: 10 Minimum Density for Interior Forest [Percent] [number] Default: 99 Search Distance Increment [number] Default: 0.0 Density from Neighbourhood [boolean] Default: True Outputs Density [Percent] [raster] Connectivity [Percent] [raster] Fragmentation [raster] Summary [table] 446 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:fragmentationalternative’, classes, class, neighborhood_min, neighborhood_max, aggregation, border, weight, density_min, density_int, level_grow, density_mean, density, connectivity, fragmentation, fragstats) See also Fragmentation classes from density and connectivity Description Parameters Density [Percent] [raster] Connectivity [Percent] [raster] Add Border [boolean] Default: True Connectivity Weighting [number] Default: 0 Minimum Density [Percent] [number] Default: 10 Minimum Density for Interior Forest [Percent] [number] Default: 99 Outputs Fragmentation [raster] Console usage processing.runalg(’saga:fragmentationclassesfromdensityandconnectivity’, density, connectivity, border, weight, density_min, density_int, fragmentation) See also Fragmentation (standard) Description 18.7. SAGA algorithm provider 447 QGIS User Guide, Release 2.6 Parameters Classification [raster] Class Identifier [number] Default: 1 Neighborhood Min [number] Default: 1 Neighborhood Max [number] Default: 3 Level Aggregation [selection] Options: • 0 — [0] average • 1 — [1] multiplicative Default: 0 Add Border [boolean] Default: True Connectivity Weighting [number] Default: 1.1 Minimum Density [Percent] [number] Default: 10 Minimum Density for Interior Forest [Percent] [number] Default: 99 Neighborhood Type [selection] Options: • 0 — [0] square • 1 — [1] circle Default: 0 Include diagonal neighbour relations [boolean] Default: True Outputs Density [Percent] [raster] Connectivity [Percent] [raster] Fragmentation [raster] Summary [table] Console usage processing.runalg(’saga:fragmentationstandard’, classes, class, neighborhood_min, neighborhood_max, aggregation, border, weight, density_min, density_int, circular, diagonal, density, connectivity, fragmentation, fragstats) 448 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Layer of extreme value Description Parameters Grids [multipleinput: rasters] Method [selection] Options: • 0 — [0] Maximum • 1 — [1] Minimum Default: 0 Outputs Result [raster] Console usage processing.runalg(’saga:layerofextremevalue’, grids, criteria, result) See also Least cost paths Description Parameters Source Point(s) [vector: point] Accumulated cost [raster] Values [multipleinput: rasters] Optional. Outputs Profile (points) [vector] Profile (lines) [vector] 18.7. SAGA algorithm provider 449 QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:leastcostpaths’, source, dem, values, points, line) See also Ordered Weighted Averaging Description Parameters Input Grids [multipleinput: rasters] Weights [fixedtable] Outputs Output Grid [raster] Console usage processing.runalg(’saga:orderedweightedaveraging’, grids, weights, output) See also Pattern analysis Description Parameters Input Grid [raster] Size of Analysis Window [selection] Options: • 0 — [0] 3 X 3 • 1 — [1] 5 X 5 • 2 — [2] 7 X 7 Default: 0 Max. Number of Classes [number] Default: 0 450 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Relative Richness [raster] Diversity [raster] Dominance [raster] Fragmentation [raster] Number of Different Classes [raster] Center Versus Neighbours [raster] Console usage processing.runalg(’saga:patternanalysis’, input, winsize, maxnumclass, relative, diversity, dominance, fragmentation, ndc, cvn) See also Soil texture classification Description Parameters Sand [raster] Optional. Silt [raster] Optional. Clay [raster] Optional. Outputs Soil Texture [raster] Sum [raster] Console usage processing.runalg(’saga:soiltextureclassification’, sand, silt, clay, texture, sum) See also . 18.7. SAGA algorithm provider 451 QGIS User Guide, Release 2.6 18.7.3 Grid calculus Function Description Parameters xmin [number] Default: 0.0 xmax [number] Default: 0.0 ymin [number] Default: 0.0 ymax [number] Default: 0.0 Formula [string] Default: (not set) Outputs Function [raster] Console usage processing.runalg(’saga:function’, xmin, xmax, ymin, ymax, formul, result) See also Fuzzify Description Parameters Grid [raster] A[number] Default: 0.0 B[number] Default: 0.0 452 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 C[number] Default: 0.0 D[number] Default: 0.0 Membership Function Type [selection] Options: • 0 — [0] linear • 1 — [1] sigmoidal • 2 — [2] j-shaped Default: 0 Adjust to Grid [boolean] Default: True Outputs Fuzzified Grid [raster] Console usage processing.runalg(’saga:fuzzify’, input, a, b, c, d, type, autofit, output) See also Fuzzy intersection (and) Description Parameters Grids [multipleinput: rasters] Operator Type [selection] Options: • 0 — [0] min(a, b) (non-interactive) • 1 — [1] a * b • 2 — [2] max(0, a + b - 1) Default: 0 Outputs Intersection [raster] 18.7. SAGA algorithm provider 453 QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:fuzzyintersectionand’, grids, type, and) See also Fuzzy union (or) Description Parameters Grids [multipleinput: rasters] Operator Type [selection] Options: • 0 — [0] max(a, b) (non-interactive) • 1 — [1] a + b - a * b • 2 — [2] min(1, a + b) Default: 0 Outputs Union [raster] Console usage processing.runalg(’saga:fuzzyunionor’, grids, type, or) See also Geometric figures Description Draws simple geometric figures. Parameters Cell Count [number] Number of cells to use. Default: 0 Cell Size [number] Size of the single cell. Default: 0 454 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Figure [selection] Type of the figure. Options: • 0 — [0] Cone (up) • 1 — [1] Cone (down) • 2 — [2] Plane Default: 0 Direction of Plane [Degree] [number] Rotation factor in degrees. Default: 0 Outputs Result [raster] The resulting layer. Console usage processing.runalg(’saga:geometricfigures’, cell_count, cell_size, figure, plane, result) See also Gradient vector from cartesian to polar coordinates Description Parameters X Component [raster] Y Component [raster] Polar Angle Units [selection] Options: • 0 — [0] radians • 1 — [1] degree Default: 0 Polar Coordinate System [selection] Options: • 0 — [0] mathematical • 1 — [1] geographical • 2 — [2] user defined Default: 0 User defined Zero Direction [number] Default: 0.0 18.7. SAGA algorithm provider 455 QGIS User Guide, Release 2.6 User defined Orientation [selection] Options: • 0 — [0] clockwise • 1 — [1] counterclockwise Default: 0 Outputs Direction [raster] Length [raster] Console usage processing.runalg(’saga:gradientvectorfromcartesiantopolarcoordinates’, dx, dy, units, system, system_zero, system_orient, dir, len) See also Gradient vector from polar to cartesian coordinates Description Parameters Direction [raster] Length [raster] Polar Angle Units [selection] Options: • 0 — [0] radians • 1 — [1] degree Default: 0 Polar Coordinate System [selection] Options: • 0 — [0] mathematical • 1 — [1] geographical • 2 — [2] user defined Default: 0 User defined Zero Direction [number] Default: 0.0 User defined Orientation [selection] Options: • 0 — [0] clockwise 456 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 1 — [1] counterclockwise Default: 0 Outputs X Component [raster] Y Component [raster] Console usage processing.runalg(’saga:gradientvectorfrompolartocartesiancoordinates’, dir, len, units, system, system_zero, system_orient, dx, dy) See also Grid difference Description Creates a new grid layer as the result of the difference between two other grid layers. Parameters A[raster] First layer. B[raster] Second layer. Outputs Difference (A - B) [raster] The resulting layer. Console usage processing.runalg(’saga:griddifference’, a, b, c) See also Grid division Description Creates a new grid layer as the result of the division between two other grid layers. Parameters Dividend [raster] First layer. Divisor [raster] Second layer. 18.7. SAGA algorithm provider 457 QGIS User Guide, Release 2.6 Outputs Quotient [raster] The resulting layer. Console usage processing.runalg(’saga:griddivision’, a, b, c) See also Grid normalisation Description Normalises the grid values according to minimum and maximum values chosen. Parameters Grid [raster] Grid to normalize. Target Range (min) [number] Minimum value. Default: 0 Target Range (max) [number] Maximum value. Default: 1 Outputs Normalised Grid [raster] The resulting layer. Console usage processing.runalg(’saga:gridnormalisation’, input, range_min, range_max, output) See also Grids product Description Parameters Grids [multipleinput: rasters] Outputs Product [raster] 458 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:gridsproduct’, grids, result) See also Grids sum Description Creates a new grid layer as the result of the sum of two or more grid layers. Parameters Grids [multipleinput: rasters] Grid layers to sum Outputs Sum [raster] The resulting layer. Console usage processing.runalg(’saga:gridssum’, grids, result) See also Grid standardisation Description Standardises the grid layer values. Parameters Grid [raster] Grid to process. Stretch Factor [number] stretching factor. Default: 1.0 Outputs Standardised Grid [raster] The resulting layer. Console usage processing.runalg(’saga:gridstandardisation’, input, stretch, output) 18.7. SAGA algorithm provider 459 QGIS User Guide, Release 2.6 See also Grid volume Description Parameters Grid [raster] Method [selection] Options: • 0 — [0] Count Only Above Base Level • 1 — [1] Count Only Below Base Level • 2 — [2] Subtract Volumes Below Base Level • 3 — [3] Add Volumes Below Base Level Default: 0 Base Level [number] Default: 0.0 Outputs Console usage processing.runalg(’saga:gridvolume’, grid, method, level) See also Metric conversions Description Performs numerical conversions of the grid values. Parameters Grid [raster] Grid to process. Conversion [selection] Conversion type. Options: • 0 — [0] radians to degree • 1 — [1] degree to radians • 2 — [2] Celsius to Fahrenheit • 3 — [3] Fahrenheit to Celsius Default: 0 460 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Converted Grid [raster] The resulting layer. Console usage processing.runalg(’saga:metricconversions’, grid, conversion, conv) See also Polynomial trend from grids Description Parameters Dependent Variables [multipleinput: rasters] Independent Variable (per Grid and Cell) [multipleinput: rasters] Optional. Independent Variable (per Grid) [fixedtable] Type of Approximated Function [selection] Options: • 0 — [0] first order polynom (linear regression) • 1 — [1] second order polynom • 2 — [2] third order polynom • 3 — [3] fourth order polynom • 4 — [4] fifth order polynom Default: 0 Outputs Polynomial Coefficients [raster] Coefficient of Determination [raster] Console usage processing.runalg(’saga:polynomialtrendfromgrids’, grids, y_grids, y_table, polynom, parms, quality) 18.7. SAGA algorithm provider 461 QGIS User Guide, Release 2.6 See also Random field Description Generates a random grid layer. Parameters Width (Cells) [number] Width of the layer in cells. Default: 100 Height (Cells) [number] Height of the layer in cells. Default: 100 Cellsize [number] Cell size to use. Default: 100.0 West [number] West coordinate of the bottom-left corner of the grid. Default: 0.0 South [number] South coordinate of the bottom-left corner of the grid. Default: 0.0 Method [selection] Statistical method used for the calculation. Options: • 0 — [0] Uniform • 1 — [1] Gaussian Default: 0 Range Min [number] Minimum cell value to use. Default: 0.0 Range Max [number] Maximum cell value to use. Default: 1.0 Arithmetic Mean [number] Mean of all the cell values to use. Default: 0.0 Standard Deviation [number] Standard deviation of all the cell values to use. Default: 1.0 Outputs Random Field [raster] The resulting layer. Console usage processing.runalg(’saga:randomfield’, nx, ny, cellsize, xmin, ymin, method, range_min, range_max, mean, stddev, output) 462 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Random terrain generation Description Parameters Radius (cells) [number] Default: 10 Iterations [number] Default: 10 Target Dimensions [selection] Options: • 0 — [0] User defined Default: 0 Grid Size [number] Default: 1.0 Cols [number] Default: 100 Rows [number] Default: 100 Outputs Grid [raster] Console usage processing.runalg(’saga:randomterraingeneration’, radius, iterations, target_type, user_cell_size, user_cols, user_rows, target_grid) See also Raster calculator Description 18.7. SAGA algorithm provider 463 QGIS User Guide, Release 2.6 Parameters Main input layer [raster] Additional layers [multipleinput: rasters] Optional. Formula [string] Default: (not set) Outputs Result [raster] Console usage processing.runalg(’saga:rastercalculator’, grids, xgrids, formula, result) See also . 18.7.4 Grid filter Dtm filter (slope-based) Description Parameters Grid to filter [raster] Search Radius [number] Default: 2 Approx. Terrain Slope [number] Default: 30.0 Use Confidence Interval [boolean] Default: True Outputs Bare Earth [raster] Removed Objects [raster] 464 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:dtmfilterslopebased’, input, radius, terrainslope, stddev, ground, nonground) See also Filter clumps Description Parameters Input Grid [raster] Min. Size [number] Default: 10 Outputs Filtered Grid [raster] Console usage processing.runalg(’saga:filterclumps’, grid, threshold, output) See also Gaussian filter Description Parameters Grid [raster] Standard Deviation [number] Default: 1 Search Mode [selection] Options: • 0 — [0] Square • 1 — [1] Circle Default: 0 Search Radius [number] Default: 3 18.7. SAGA algorithm provider 465 QGIS User Guide, Release 2.6 Outputs Filtered Grid [raster] Console usage processing.runalg(’saga:gaussianfilter’, input, sigma, mode, radius, result) See also Laplacian filter Description Parameters Grid [raster] Method [selection] Options: • 0 — [0] standard kernel 1 • 1 — [1] standard kernel 2 • 2 — [2] Standard kernel 3 • 3 — [3] user defined kernel Default: 0 Standard Deviation (Percent of Radius) [number] Default: 0 Radius [number] Default: 1 Search Mode [selection] Options: • 0 — [0] square • 1 — [1] circle Default: 0 Outputs Filtered Grid [raster] Console usage processing.runalg(’saga:laplacianfilter’, input, method, sigma, radius, mode, result) 466 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Majority filter Description Parameters Grid [raster] Search Mode [selection] Options: • 0 — [0] Square • 1 — [1] Circle Default: 0 Radius [number] Default: 1 Threshold [Percent] [number] Default: 0 Outputs Filtered Grid [raster] Console usage processing.runalg(’saga:majorityfilter’, input, mode, radius, threshold, result) See also Morphological filter Description Parameters Grid [raster] Search Mode [selection] Options: • 0 — [0] Square • 1 — [1] Circle Default: 0 18.7. SAGA algorithm provider 467 QGIS User Guide, Release 2.6 Radius [number] Default: 1 Method [selection] Options: • 0 — [0] Dilation • 1 — [1] Erosion • 2 — [2] Opening • 3 — [3] Closing Default: 0 Outputs Filtered Grid [raster] Console usage processing.runalg(’saga:morphologicalfilter’, input, mode, radius, method, result) See also Multi direction lee filter Description Parameters Grid [raster] Estimated Noise (absolute) [number] Default: 1.0 Estimated Noise (relative) [number] Default: 1.0 Weighted [boolean] Default: True Method [selection] Options: • 0 — [0] noise variance given as absolute value • 1 — [1] noise variance given relative to mean standard deviation • 2 — [2] original calculation (Ringeler) Default: 0 468 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Filtered Grid [raster] Minimum Standard Deviation [raster] Direction of Minimum Standard Deviation [raster] Console usage processing.runalg(’saga:multidirectionleefilter’, input, noise_abs, noise_rel, weighted, method, result, stddev, dir) See also Rank filter Description Parameters Grid [raster] Search Mode [selection] Options: • 0 — [0] Square • 1 — [1] Circle Default: 0 Radius [number] Default: 1 Rank [Percent] [number] Default: 50 Outputs Filtered Grid [raster] Console usage processing.runalg(’saga:rankfilter’, input, mode, radius, rank, result) See also Simple filter Description 18.7. SAGA algorithm provider 469 QGIS User Guide, Release 2.6 Parameters Grid [raster] Search Mode [selection] Options: • 0 — [0] Square • 1 — [1] Circle Default: 0 Filter [selection] Options: • 0 — [0] Smooth • 1 — [1] Sharpen • 2 — [2] Edge Default: 0 Radius [number] Default: 2 Outputs Filtered Grid [raster] Console usage processing.runalg(’saga:simplefilter’, input, mode, method, radius, result) See also User defined filter Description Parameters Grid [raster] Filter Matrix [table] Optional. Default Filter Matrix (3x3) [fixedtable] Outputs Filtered Grid [raster] 470 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:userdefinedfilter’, input, filter, filter_3x3, result) See also . 18.7.5 Grid gridding Inverse distance weighted Description Inverse distance grid interpolation from irregular distributed points. Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Distance Weighting [selection] Options: • 0 — [0] inverse distance to a power • 1 — [1] linearly decreasing within search radius • 2 — [2] exponential weighting scheme • 3 — [3] gaussian weighting scheme Default: 0 Inverse Distance Power [number] Default: 2 Exponential and Gaussian Weighting Bandwidth [number] Default: 1 Search Range [selection] Options: • 0 — [0] search radius (local) • 1 — [1] no search radius (global) Default: 0 Search Radius [number] Default: 100.0 18.7. SAGA algorithm provider 471 QGIS User Guide, Release 2.6 Search Mode [selection] Options: • 0 — [0] all directions • 1 — [1] quadrants Default: 0 Number of Points [selection] Options: • 0 — [0] maximum number of points • 1 — [1] all points Default: 0 Maximum Number of Points [number] Default: 10 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:inversedistanceweighted’, shapes, field, target, weighting, power, bandwidth, range, radius, mode, points, npoints, output_extent, user_size, user_grid) See also Kernel density estimation Description Parameters Points [vector: point] Weight [tablefield: any] Radius [number] Default: 10 Kernel [selection] Options: • 0 — [0] quartic kernel • 1 — [1] gaussian kernel 472 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Default: 0 Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:kerneldensityestimation’, points, population, radius, kernel, target, output_extent, user_size, user_grid) See also Modifed quadratic shepard Description Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Quadratic Neighbors [number] Default: 13 Weighting Neighbors [number] Default: 19 Left [number] Default: 0.0 Right [number] Default: 0.0 18.7. SAGA algorithm provider 473 QGIS User Guide, Release 2.6 Bottom [number] Default: 0.0 Top [number] Default: 0.0 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:modifedquadraticshepard’, shapes, field, target, quadratic_neighbors, weighting_neighbors, user_xmin, user_xmax, user_ymin, user_ymax, user_size, user_grid) See also Natural neighbour Description Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Sibson [boolean] Default: True Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] 474 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:naturalneighbour’, shapes, field, target, sibson, output_extent, user_size, user_grid) See also Nearest neighbour Description Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:nearestneighbour’, shapes, field, target, output_extent, user_size, user_grid) See also Shapes to grid Description 18.7. SAGA algorithm provider 475 QGIS User Guide, Release 2.6 Parameters Shapes [vector: any] Attribute [tablefield: any] Method for Multiple Values [selection] Options: • 0 — [0] first • 1 — [1] last • 2 — [2] minimum • 3 — [3] maximum • 4 — [4] mean Default: 0 Method for Lines [selection] Options: • 0 — [0] thin • 1 — [1] thick Default: 0 Preferred Target Grid Type [selection] Options: • 0 — [0] Integer (1 byte) • 1 — [1] Integer (2 byte) • 2 — [2] Integer (4 byte) • 3 — [3] Floating Point (4 byte) • 4 — [4] Floating Point (8 byte) Default: 0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:shapestogrid’, input, field, multiple, line_type, grid_type, output_extent, user_size, user_grid) 476 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Triangulation Description Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:triangulation’, shapes, field, target, output_extent, user_size, user_grid) See also . 18.7.6 Grid spline B-spline approximation Description 18.7. SAGA algorithm provider 477 QGIS User Guide, Release 2.6 Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Resolution [number] Default: 1.0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:bsplineapproximation’, shapes, field, target, level, output_extent, user_size, user_grid) See also Cubic spline approximation Description Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Minimal Number of Points [number] Default: 3 Maximal Number of Points [number] Default: 20 478 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Points per Square [number] Default: 5 Tolerance [number] Default: 140.0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:cubicsplineapproximation’, shapes, field, target, npmin, npmax, nppc, k, output_extent, user_size, user_grid) See also Multilevel b-spline interpolation (from grid) Description Parameters Grid [raster] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Method [selection] Options: • 0 — [0] without B-spline refinement • 1 — [1] with B-spline refinement Default: 0 Threshold Error [number] Default: 0.0001 Maximum Level [number] Default: 11.0 Data Type [selection] Options: 18.7. SAGA algorithm provider 479 QGIS User Guide, Release 2.6 • 0 — [0] same as input grid • 1 — [1] floating point Default: 0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:multilevelbsplineinterpolationfromgrid’, gridpoints, target, method, epsilon, level_max, datatype, output_extent, user_size, user_grid) See also Multilevel b-spline interpolation Description Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Method [selection] Options: • 0 — [0] without B-spline refinement • 1 — [1] with B-spline refinement Default: 0 Threshold Error [number] Default: 0.0001 Maximum Level [number] Default: 11.0 Output extent [extent] Default: 0,1,0,1 480 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:multilevelbsplineinterpolation’, shapes, field, target, method, epsilon, level_max, output_extent, user_size, user_grid) See also Thin plate spline (global) Description Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Regularisation [number] Default: 0.0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:thinplatesplineglobal’, shapes, field, target, regul, output_extent, user_size, user_grid) 18.7. SAGA algorithm provider 481 QGIS User Guide, Release 2.6 See also Thin plate spline (local) Description Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Regularisation [number] Default: 0.0001 Search Radius [number] Default: 100.0 Search Mode [selection] Options: • 0 — [0] all directions • 1 — [1] quadrants Default: 0 Points Selection [selection] Options: • 0 — [0] all points in search radius • 1 — [1] maximum number of points Default: 0 Maximum Number of Points [number] Default: 10 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] 482 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:thinplatesplinelocal’, shapes, field, target, regul, radius, mode, select, maxpoints, output_extent, user_size, user_grid) See also Thin plate spline (tin) Description Parameters Points [vector: point] Attribute [tablefield: any] Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Regularisation [number] Default: 0.0 Neighbourhood [selection] Options: • 0 — [0] immediate • 1 — [1] level 1 • 2 — [2] level 2 Default: 0 Add Frame [boolean] Default: True Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] Console usage processing.runalg(’saga:thinplatesplinetin’, shapes, field, target, regul, level, frame, output_extent, user_size, user_grid) 18.7. SAGA algorithm provider 483 QGIS User Guide, Release 2.6 See also . 18.7.7 Grid tools Aggregate Description Parameters Grid [raster] Aggregation Size [number] Default: 3 Method [selection] Options: • 0 — [0] Sum • 1 — [1] Min • 2 — [2] Max Default: 0 Outputs Console usage processing.runalg(’saga:aggregate’, input, size, method) See also Change grid values Description Parameters Grid [raster] Replace Condition [selection] Options: • 0 — [0] Grid value equals low value • 1 — [1] Low value < grid value < high value 484 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 2 — [2] Low value <= grid value < high value Default: 0 Lookup Table [fixedtable] Outputs Changed Grid [raster] Console usage processing.runalg(’saga:changegridvalues’, grid_in, method, lookup, grid_out) See also Close gaps Description Parameters Grid [raster] Mask [raster] Optional. Tension Threshold [number] Default: 0.1 Outputs Changed Grid [raster] Console usage processing.runalg(’saga:closegaps’, input, mask, threshold, result) See also Close gaps with spline Description 18.7. SAGA algorithm provider 485 QGIS User Guide, Release 2.6 Parameters Grid [raster] Mask [raster] Optional. Only Process Gaps with Less Cells [number] Default: 0 Maximum Points [number] Default: 1000 Number of Points for Local Interpolation [number] Default: 10 Extended Neighourhood [boolean] Default: True Neighbourhood [selection] Options: • 0 — [0] Neumann • 1 — [1] Moore Default: 0 Radius (Cells) [number] Default: 0 Relaxation [number] Default: 0.0 Outputs Closed Gaps Grid [raster] Console usage processing.runalg(’saga:closegapswithspline’, grid, mask, maxgapcells, maxpoints, localpoints, extended, neighbours, radius, relaxation, closed) See also Close one cell gaps Description Parameters Grid [raster] 486 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Changed Grid [raster] Console usage processing.runalg(’saga:closeonecellgaps’, input, result) See also Convert data storage type Description Parameters Grid [raster] Data storage type [selection] Options: • 0 — [0] bit • 1 — [1] unsigned 1 byte integer • 2 — [2] signed 1 byte integer • 3 — [3] unsigned 2 byte integer • 4 — [4] signed 2 byte integer • 5 — [5] unsigned 4 byte integer • 6 — [6] signed 4 byte integer • 7 — [7] 4 byte floating point number • 8 — [8] 8 byte floating point number Default: 0 Outputs Converted Grid [raster] Console usage processing.runalg(’saga:convertdatastoragetype’, input, type, output) 18.7. SAGA algorithm provider 487 QGIS User Guide, Release 2.6 See also Crop to data Description Parameters Input layer [raster] Outputs Cropped layer [raster] Console usage processing.runalg(’saga:croptodata’, input, output) See also Grid buffer Description Parameters Features Grid [raster] Distance [number] Default: 1000 Buffer Distance [selection] Options: • 0 — [0] Fixed • 1 — [1] Cell value Default: 0 Outputs Buffer Grid [raster] Console usage 488 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 processing.runalg(’saga:gridbuffer’, features, dist, buffertype, buffer) See also Grid masking Description Parameters Grid [raster] Mask [raster] Outputs Masked Grid [raster] Console usage processing.runalg(’saga:gridmasking’, grid, mask, masked) See also Grid orientation Description Parameters Grid [raster] Method [selection] Options: • 0 — [0] Copy • 1 — [1] Flip • 2 — [2] Mirror • 3 — [3] Invert Default: 0 Outputs Changed Grid [raster] 18.7. SAGA algorithm provider 489 QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:gridorientation’, input, method, result) See also Grid proximity buffer Description Parameters Source Grid [raster] Buffer distance [number] Default: 500.0 Equidistance [number] Default: 100.0 Outputs Distance Grid [raster] Allocation Grid [raster] Buffer Grid [raster] Console usage processing.runalg(’saga:gridproximitybuffer’, source, dist, ival, distance, alloc, buffer) See also Grid shrink/expand Description Parameters Grid [raster] Operation [selection] Options: • 0 — [0] Shrink • 1 — [1] Expand 490 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Default: 0 Search Mode [selection] Options: • 0 — [0] Square • 1 — [1] Circle Default: 0 Radius [number] Default: 1 Method [selection] Options: • 0 — [0] min • 1 — [1] max • 2 — [2] mean • 3 — [3] majority Default: 0 Outputs Result Grid [raster] Console usage processing.runalg(’saga:gridshrinkexpand’, input, operation, mode, radius, method_expand, result) See also Invert data/no-data Description Parameters Grid [raster] Outputs Result [raster] Console usage processing.runalg(’saga:invertdatanodata’, input, output) 18.7. SAGA algorithm provider 491 QGIS User Guide, Release 2.6 See also Merge raster layers Description Parameters Grids to Merge [multipleinput: rasters] Preferred data storage type [selection] Options: • 0 — [0] 1 bit • 1 — [1] 1 byte unsigned integer • 2 — [2] 1 byte signed integer • 3 — [3] 2 byte unsigned integer • 4 — [4] 2 byte signed integer • 5 — [5] 4 byte unsigned integer • 6 — [6] 4 byte signed integer • 7 — [7] 4 byte floating point • 8 — [8] 8 byte floating point Default: 0 Interpolation [selection] Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 Overlapping Cells [selection] Options: • 0 — [0] mean value • 1 — [1] first value in order of grid list Default: 0 Outputs Merged Grid [raster] 492 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:mergerasterlayers’, grids, type, interpol, overlap, merged) See also Patching Description Parameters Grid [raster] Patch Grid [raster] Interpolation Method [selection] Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 Outputs Completed Grid [raster] Console usage processing.runalg(’saga:patching’, original, additional, interpolation, completed) See also Proximity grid Description Parameters Features [raster] 18.7. SAGA algorithm provider 493 QGIS User Guide, Release 2.6 Outputs Distance [raster] Direction [raster] Allocation [raster] Console usage processing.runalg(’saga:proximitygrid’, features, distance, direction, allocation) See also Reclassify grid values Description Parameters Grid [raster] Method [selection] Options: • 0 — [0] single • 1 — [1] range • 2 — [2] simple table Default: 0 old value (for single value change) [number] Default: 0.0 new value (for single value change) [number] Default: 1.0 operator (for single value change) [selection] Options: • 0 — [0] = • 1 — [1] < • 2 — [2] <= • 3 — [3] >= • 4 — [4] > Default: 0 minimum value (for range) [number] Default: 0.0 494 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 maximum value (for range) [number] Default: 1.0 new value(for range) [number] Default: 2.0 operator (for range) [selection] Options: • 0 — [0] <= • 1 — [1] < Default: 0 Lookup Table [fixedtable] operator (for table) [selection] Options: • 0 — [0] min <= value < max • 1 — [1] min <= value <= max • 2 — [2] min < value <= max • 3 — [3] min < value < max Default: 0 replace no data values [boolean] Default: True new value for no data values [number] Default: 0.0 replace other values [boolean] Default: True new value for other values [number] Default: 0.0 Outputs Reclassified Grid [raster] Console usage processing.runalg(’saga:reclassifygridvalues’, input, method, old, new, soperator, min, max, rnew, roperator, retab, toperator, nodataopt, nodata, otheropt, others, result) See also Resampling Description 18.7. SAGA algorithm provider 495 QGIS User Guide, Release 2.6 Parameters Grid [raster] Preserve Data Type [boolean] Default: True Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Interpolation Method (Scale Up) [selection] Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation • 5 — [5] Mean Value • 6 — [6] Mean Value (cell area weighted) • 7 — [7] Minimum Value • 8 — [8] Maximum Value • 9 — [9] Majority Default: 0 Interpolation Method (Scale Down) [selection] Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 Output extent [extent] Default: 0,1,0,1 Cellsize [number] Default: 100.0 Outputs Grid [raster] 496 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:resampling’, input, keep_type, target, scale_up_method, scale_down_method, output_extent, user_size, user_grid) See also Sort grid Description Parameters Input Grid [raster] Down sort [boolean] Default: True Outputs Sorted Grid [raster] Console usage processing.runalg(’saga:sortgrid’, grid, down, output) See also Split RGB bands Description Parameters Input layer [raster] Outputs Output R band layer [raster] Output G band layer [raster] Output B band layer [raster] 18.7. SAGA algorithm provider 497 QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:splitrgbbands’, input, r, g, b) See also Threshold buffer Description Parameters Features Grid [raster] Value Grid [raster] Threshold Grid [raster] Optional. Threshold [number] Default: 0.0 Threshold Type [selection] Options: • 0 — [0] Absolute • 1 — [1] Relative from cell value Default: 0 Outputs Buffer Grid [raster] Console usage processing.runalg(’saga:thresholdbuffer’, features, value, thresholdgrid, threshold, thresholdtype, buffer) See also . 18.7.8 Grid visualization Histogram surface Description 498 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Grid [raster] Method [selection] Options: • 0 — [0] rows • 1 — [1] columns • 2 — [2] circle Default: 0 Outputs Histogram [raster] Console usage processing.runalg(’saga:histogramsurface’, grid, method, hist) See also Rgb composite Description Parameters R[raster] G[raster] B[raster] Method for R value [selection] Options: • 0 — 0 - 255 • 1 — Rescale to 0 - 255 • 2 — User defined rescale • 3 — Percentiles • 4 — Percentage of standard deviation Default: 0 Method for G value [selection] Options: • 0 — 0 - 255 • 1 — Rescale to 0 - 255 18.7. SAGA algorithm provider 499 QGIS User Guide, Release 2.6 • 2 — User defined rescale • 3 — Percentiles • 4 — Percentage of standard deviation Default: 0 Method for B value [selection] Options: • 0 — 0 - 255 • 1 — Rescale to 0 - 255 • 2 — User defined rescale • 3 — Percentiles • 4 — Percentage of standard deviation Default: 0 Rescale Range for RED min [number] Default: 0 Rescale Range for RED max [number] Default: 255 Percentiles Range for RED max [number] Default: 1 Percentiles Range for RED max [number] Default: 99 Percentage of standard deviation for RED [number] Default: 150.0 Rescale Range for GREEN min [number] Default: 0 Rescale Range for GREEN max [number] Default: 255 Percentiles Range for GREEN max [number] Default: 1 Percentiles Range for GREEN max [number] Default: 99 Percentage of standard deviation for GREEN [number] Default: 150.0 Rescale Range for BLUE min [number] Default: 0 Rescale Range for BLUE max [number] Default: 255 Percentiles Range for BLUE max [number] Default: 1 500 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Percentiles Range for BLUE max [number] Default: 99 Percentage of standard deviation for BLUE [number] Default: 150.0 Outputs Output RGB [raster] Console usage processing.runalg(’saga:rgbcomposite’, grid_r, grid_g, grid_b, r_method, g_method, b_method, r_range_min, r_range_max, r_perctl_min, r_perctl_max, r_percent, g_range_min, g_range_max, g_perctl_min, g_perctl_max, g_percent, b_range_min, b_range_max, b_perctl_min, b_perctl_max, b_percent, grid_rgb) See also . 18.7.9 Imagery classification Change detection Description Parameters Initial State [raster] Look-up Table [table] Optional. Value [tablefield: any] Value (Maximum) [tablefield: any] Name [tablefield: any] Final State [raster] Look-up Table [table] Optional. Value [tablefield: any] Value (Maximum) [tablefield: any] Name [tablefield: any] Report Unchanged Classes [boolean] Default: True Output as... [selection] Options: 18.7. SAGA algorithm provider 501 QGIS User Guide, Release 2.6 • 0 — [0] cells • 1 — [1] percent • 2 — [2] area Default: 0 Outputs Changes [raster] Changes [table] Console usage processing.runalg(’saga:changedetection’, initial, ini_lut, ini_lut_min, ini_lut_max, ini_lut_nam, final, fin_lut, fin_lut_min, fin_lut_max, fin_lut_nam, nochange, output, change, changes) See also Cluster analysis for grids Description Parameters Grids [multipleinput: rasters] Method [selection] Options: • 0 — [0] Iterative Minimum Distance (Forgy 1965) • 1 — [1] Hill-Climbing (Rubin 1967) • 2 — [2] Combined Minimum Distance / Hillclimbing Default: 0 Clusters [number] Default: 5 Normalise [boolean] Default: True Old Version [boolean] Default: True Outputs Clusters [raster] Statistics [table] 502 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:clusteranalysisforgrids’, grids, method, ncluster, normalise, oldversion, cluster, statistics) See also Supervised classification Description Parameters Grids [multipleinput: rasters] Training Areas [vector: polygon] Class Identifier [tablefield: any] Method [selection] Options: • 0 — [0] Binary Encoding • 1 — [1] Parallelepiped • 2 — [2] Minimum Distance • 3 — [3] Mahalanobis Distance • 4 — [4] Maximum Likelihood • 5 — [5] Spectral Angle Mapping • 6 — [6] Winner Takes All Default: 0 Normalise [boolean] Default: True Distance Threshold [number] Default: 0.0 Probability Threshold (Percent) [number] Default: 0.0 Probability Reference [selection] Options: • 0 — [0] absolute • 1 — [1] relative Default: 0 Spectral Angle Threshold (Degree) [number] Default: 0.0 18.7. SAGA algorithm provider 503 QGIS User Guide, Release 2.6 Outputs Class Information [table] Classification [raster] Quality [raster] Console usage processing.runalg(’saga:supervisedclassification’, grids, roi, roi_id, method, normalise, threshold_dist, threshold_prob, relative_prob, threshold_angle, class_info, classes, quality) See also . 18.7.10 Imagery RGA Fast region growing algorithm Description Parameters Input Grids [multipleinput: rasters] Seeds Grid [raster] Smooth Rep [raster] Optional. Outputs Segmente [raster] Mean [raster] Console usage processing.runalg(’saga:fastregiongrowingalgorithm’, input, start, rep, result, mean) See also . 504 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 18.7.11 Imagery segmentation Grid skeletonization Description Parameters Grid [raster] Method [selection] Options: • 0 — [0] Standard • 1 — [1] Hilditch’s Algorithm • 2 — [2] Channel Skeleton Default: 0 Initialisation [selection] Options: • 0 — [0] Less than • 1 — [1] Greater than Default: 0 Threshold (Init.) [number] Default: 0.0 Convergence [number] Default: 3.0 Outputs Skeleton [raster] Skeleton [vector] Console usage processing.runalg(’saga:gridskeletonization’, input, method, init_method, init_threshold, convergence, result, vector) See also Seed generation Description 18.7. SAGA algorithm provider 505 QGIS User Guide, Release 2.6 Parameters Features [multipleinput: rasters] Bandwidth (Cells) [number] Default: 2 Type of Surface [selection] Options: • 0 — [0] smoothed surface • 1 — [1] variance (a) • 2 — [2] variance (b) Default: 0 Extraction of... [selection] Options: • 0 — [0] minima • 1 — [1] maxima • 2 — [2] minima and maxima Default: 0 Feature Aggregation [selection] Options: • 0 — [0] additive • 1 — [1] multiplicative Default: 0 Normalized [boolean] Default: True Outputs Surface [raster] Seeds Grid [raster] Seeds [vector] Console usage processing.runalg(’saga:seedgeneration’, grids, factor, type_surface, type_seeds, type_merge, normalize, surface, seeds_grid, seeds) See also Simple region growing Description 506 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Seeds [raster] Features [multipleinput: rasters] Method [selection] Options: • 0 — [0] feature space and position • 1 — [1] feature space Default: 0 Neighbourhood [selection] Options: • 0 — [0] 4 (von Neumann) • 1 — [1] 8 (Moore) Default: 0 Variance in Feature Space [number] Default: 1.0 Variance in Position Space [number] Default: 1.0 Threshold - Similarity [number] Default: 0.0 Refresh [boolean] Default: True Leaf Size (for Speed Optimisation) [number] Default: 256 Outputs Segments [raster] Similarity [raster] Seeds [table] Console usage processing.runalg(’saga:simpleregiongrowing’, seeds, features, method, neighbour, sig_1, sig_2, threshold, refresh, leafsize, segments, similarity, table) See also Watershed segmentation Description 18.7. SAGA algorithm provider 507 QGIS User Guide, Release 2.6 Parameters Grid [raster] Output [selection] Options: • 0 — [0] Seed Value • 1 — [1] Segment ID Default: 0 Method [selection] Options: • 0 — [0] Minima • 1 — [1] Maxima Default: 0 Join Segments based on Threshold Value [selection] Options: • 0 — [0] do not join • 1 — [1] seed to saddle difference • 2 — [2] seeds difference Default: 0 Threshold [number] Default: 0 Allow Edge Pixels to be Seeds [boolean] Default: True Borders [boolean] Default: True Outputs Segments [raster] Seed Points [vector] Borders [raster] Console usage processing.runalg(’saga:watershedsegmentation’, grid, output, down, join, threshold, edge, bborders, segments, seeds, borders) See also . 508 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 18.7.12 Imagery tools Vegetation index[distance based] Description Parameters Near Infrared Band [raster] Red Band [raster] Slope of the soil line [number] Default: 0.0 Intercept of the soil line [number] Default: 0.0 Outputs PVI (Richardson and Wiegand) [raster] PVI (Perry & Lautenschlager) [raster] PVI (Walther & Shabaani) [raster] PVI (Qi, et al) [raster] Console usage processing.runalg(’saga:vegetationindexdistancebased’, nir, red, slope, intercept, pvi, pvi1, pvi2, pvi3) See also Vegetation index[slope based] Description Parameters Near Infrared Band [raster] Red Band [raster] 18.7. SAGA algorithm provider 509 QGIS User Guide, Release 2.6 Outputs Normalized Difference Vegetation Index [raster] Ratio Vegetation Index [raster] Transformed Vegetation Index [raster] Corrected Transformed Vegetation Index [raster] Thiam’s Transformed Vegetation Index [raster] Normalized Ratio Vegetation Index [raster] Console usage processing.runalg(’saga:vegetationindexslopebased’, nir, red, ndvi, ratio, tvi, ctvi, ttvi, nratio) See also . 18.7.13 Kriging Ordinary kriging (global) Description Parameters Points [vector: point] Attribute [tablefield: any] Create Variance Grid [boolean] Default: True Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Variogram Model [selection] Options: • 0 — [0] Spherical Model • 1 — [1] Exponential Model • 2 — [2] Gaussian Model • 3 — [3] Linear Regression • 4 — [4] Exponential Regression • 5 — [5] Power Function Regression 510 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Default: 0 Block Kriging [boolean] Default: True Block Size [number] Default: 100 Logarithmic Transformation [boolean] Default: True Nugget [number] Default: 0.0 Sill [number] Default: 0.0 Range [number] Default: 0.0 Linear Regression [number] Default: 1.0 Exponential Regression [number] Default: 0.1 Power Function - A [number] Default: 1.0 Power Function - B [number] Default: 0.5 Grid Size [number] Default: 1.0 Fit Extent [boolean] Default: True Output extent [extent] Default: 0,1,0,1 Outputs Grid [raster] Variance [raster] Console usage processing.runalg(’saga:ordinarykrigingglobal’, shapes, field, bvariance, target, model, block, dblock, blog, nugget, sill, range, lin_b, exp_b, pow_a, pow_b, user_cell_size, user_fit_extent, output_extent, grid, variance) 18.7. SAGA algorithm provider 511 QGIS User Guide, Release 2.6 See also Ordinary kriging Description Parameters Points [vector: point] Attribute [tablefield: any] Create Variance Grid [boolean] Default: True Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Variogram Model [selection] Options: • 0 — [0] Spherical Model • 1 — [1] Exponential Model • 2 — [2] Gaussian Model • 3 — [3] Linear Regression • 4 — [4] Exponential Regression • 5 — [5] Power Function Regression Default: 0 Block Kriging [boolean] Default: True Block Size [number] Default: 100 Logarithmic Transformation [boolean] Default: True Nugget [number] Default: 0.0 Sill [number] Default: 10.0 Range [number] Default: 100.0 Linear Regression [number] Default: 1.0 512 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Exponential Regression [number] Default: 0.1 Power Function - A [number] Default: 1 Power Function - B [number] Default: 0.5 Maximum Search Radius (map units) [number] Default: 1000.0 Min.Number of m_Points [number] Default: 4 Max. Number of m_Points [number] Default: 20 Grid Size [number] Default: 1.0 Fit Extent [boolean] Default: True Output extent [extent] Default: 0,1,0,1 Outputs Grid [raster] Variance [raster] Console usage processing.runalg(’saga:ordinarykriging’, shapes, field, bvariance, target, model, block, dblock, blog, nugget, sill, range, lin_b, exp_b, pow_a, pow_b, maxradius, npoints_min, npoints_max, user_cell_size, user_fit_extent, output_extent, grid, variance) See also Universal kriging (global) Description Parameters Points [vector: point] Attribute [tablefield: any] Create Variance Grid [boolean] Default: True 18.7. SAGA algorithm provider 513 QGIS User Guide, Release 2.6 Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Variogram Model [selection] Options: • 0 — [0] Spherical Model • 1 — [1] Exponential Model • 2 — [2] Gaussian Model • 3 — [3] Linear Regression • 4 — [4] Exponential Regression • 5 — [5] Power Function Regression Default: 0 Block Kriging [boolean] Default: True Block Size [number] Default: 100 Logarithmic Transformation [boolean] Default: True Nugget [number] Default: 0.0 Sill [number] Default: 0.0 Range [number] Default: 0.0 Linear Regression [number] Default: 1 Exponential Regression [number] Default: 0.5 Power Function - A [number] Default: 1.0 Power Function - B [number] Default: 0.1 Grids [multipleinput: rasters] Grid Interpolation [selection] Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation 514 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 Grid Size [number] Default: 1.0 Fit Extent [boolean] Default: True Output extent [extent] Default: 0,1,0,1 Outputs Grid [raster] Variance [raster] Console usage processing.runalg(’saga:universalkrigingglobal’, shapes, field, bvariance, target, model, block, dblock, blog, nugget, sill, range, lin_b, exp_b, pow_a, pow_b, grids, interpol, user_cell_size, user_fit_extent, output_extent, grid, variance) See also Universal kriging Description Parameters Points [vector: point] Attribute [tablefield: any] Create Variance Grid [boolean] Default: True Target Grid [selection] Options: • 0 — [0] user defined Default: 0 Variogram Model [selection] Options: • 0 — [0] Spherical Model • 1 — [1] Exponential Model • 2 — [2] Gaussian Model • 3 — [3] Linear Regression 18.7. SAGA algorithm provider 515 QGIS User Guide, Release 2.6 • 4 — [4] Exponential Regression • 5 — [5] Power Function Regression Default: 0 Block Kriging [boolean] Default: True Block Size [number] Default: 100 Logarithmic Transformation [boolean] Default: True Nugget [number] Default: 0.0 Sill [number] Default: 0.0 Range [number] Default: 0.0 Linear Regression [number] Default: 1.0 Exponential Regression [number] Default: 0.1 Power Function - A [number] Default: 1 Power Function - B [number] Default: 0.5 Grids [multipleinput: rasters] Grid Interpolation [selection] Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 Min.Number of m_Points [number] Default: 4 Max. Number of m_Points [number] Default: 20 Maximum Search Radius (map units) [number] Default: 1000.0 516 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Grid Size [number] Default: 1.0 Fit Extent [boolean] Default: True Output extent [extent] Default: 0,1,0,1 Outputs Grid [raster] Variance [raster] Console usage processing.runalg(’saga:universalkriging’, shapes, field, bvariance, target, model, block, dblock, blog, nugget, sill, range, lin_b, exp_b, pow_a, pow_b, grids, interpol, npoints_min, npoints_max, maxradius, user_cell_size, user_fit_extent, output_extent, grid, variance) See also . 18.7.14 Shapes grid Add grid values to points Description Creates a new vector layer as a result of the union of a points layer with the interpolated value of one or more base background grid layer(s). This way, the new layer created will have a new column in the attribute table that reflects the interpolated value of the background grid. Parameters Points [vector: point] Input layer. Grids [multipleinput: rasters] Background grid layer(s) Interpolation [selection] interpolation method to use. Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 18.7. SAGA algorithm provider 517 QGIS User Guide, Release 2.6 Outputs Result [vector] The resulting layer. Console usage processing.runalg(’saga:addgridvaluestopoints’, shapes, grids, interpol, result) See also Add grid values to shapes Description Parameters Shapes [vector: any] Grids [multipleinput: rasters] Interpolation [selection] Options: • 0 — [0] Nearest Neighbor • 1 — [1] Bilinear Interpolation • 2 — [2] Inverse Distance Interpolation • 3 — [3] Bicubic Spline Interpolation • 4 — [4] B-Spline Interpolation Default: 0 Outputs Result [vector] Console usage processing.runalg(’saga:addgridvaluestoshapes’, shapes, grids, interpol, result) See also Clip grid with polygon Description 518 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input [raster] Polygons [vector: polygon] Outputs Output [raster] Console usage processing.runalg(’saga:clipgridwithpolygon’, input, polygons, output) See also Contour lines from grid Description Parameters Grid [raster] Minimum Contour Value [number] Default: 0.0 Maximum Contour Value [number] Default: 10000.0 Equidistance [number] Default: 100.0 Outputs Contour Lines [vector] Console usage processing.runalg(’saga:contourlinesfromgrid’, input, zmin, zmax, zstep, contour) See also Gradient vectors from directional components Description 18.7. SAGA algorithm provider 519 QGIS User Guide, Release 2.6 Parameters X Component [raster] Y Component [raster] Step [number] Default: 1 Size Range Min [number] Default: 25.0 Size Range Max [number] Default: 100.0 Aggregation [selection] Options: • 0 — [0] nearest neighbour • 1 — [1] mean value Default: 0 Style [selection] Options: • 0 — [0] simple line • 1 — [1] arrow • 2 — [2] arrow (centered to cell) Default: 0 Outputs Gradient Vectors [vector] Console usage processing.runalg(’saga:gradientvectorsfromdirectionalcomponents’, x, y, step, size_min, size_max, aggr, style, vectors) See also Gradient vectors from direction and length Description Parameters Direction [raster] Length [raster] 520 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Step [number] Default: 1 Size Range Min [number] Default: 25.0 Size Range Max [number] Default: 100.0 Aggregation [selection] Options: • 0 — [0] nearest neighbour • 1 — [1] mean value Default: 0 Style [selection] Options: • 0 — [0] simple line • 1 — [1] arrow • 2 — [2] arrow (centered to cell) Default: 0 Outputs Gradient Vectors [vector] Console usage processing.runalg(’saga:gradientvectorsfromdirectionandlength’, dir, len, step, size_min, size_max, aggr, style, vectors) See also Gradient vectors from surface Description Parameters Surface [raster] Step [number] Default: 1 Size Range Min [number] Default: 25.0 Size Range Max [number] Default: 100.0 18.7. SAGA algorithm provider 521 QGIS User Guide, Release 2.6 Aggregation [selection] Options: • 0 — [0] nearest neighbour • 1 — [1] mean value Default: 0 Style [selection] Options: • 0 — [0] simple line • 1 — [1] arrow • 2 — [2] arrow (centered to cell) Default: 0 Outputs Gradient Vectors [vector] Console usage processing.runalg(’saga:gradientvectorsfromsurface’, surface, step, size_min, size_max, aggr, style, vectors) See also Grid statistics for polygons Description Parameters Grids [multipleinput: rasters] Polygons [vector: polygon] Number of Cells [boolean] Default: True Minimum [boolean] Default: True Maximum [boolean] Default: True Range [boolean] Default: True Sum [boolean] Default: True 522 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Mean [boolean] Default: True Variance [boolean] Default: True Standard Deviation [boolean] Default: True Quantiles [number] Default: 0 Outputs Statistics [vector] Console usage processing.runalg(’saga:gridstatisticsforpolygons’, grids, polygons, count, min, max, range, sum, mean, var, stddev, quantile, result) See also Grid values to points (randomly) Description Parameters Grid [raster] Frequency [number] Default: 100 Outputs Points [vector] Console usage processing.runalg(’saga:gridvaluestopointsrandomly’, grid, freq, points) See also Grid values to points Description 18.7. SAGA algorithm provider 523 QGIS User Guide, Release 2.6 Parameters Grids [multipleinput: rasters] Polygons [vector: any] Optional. Exclude NoData Cells [boolean] Default: True Type [selection] Options: • 0 — [0] nodes • 1 — [1] cells Default: 0 Outputs Shapes [vector] Console usage processing.runalg(’saga:gridvaluestopoints’, grids, polygons, nodata, type, shapes) See also Local minima and maxima Description Parameters Grid [raster] Outputs Minima [vector] Maxima [vector] Console usage processing.runalg(’saga:localminimaandmaxima’, grid, minima, maxima) 524 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Vectorising grid classes Description Parameters Grid [raster] Class Selection [selection] Options: • 0 — [0] one single class specified by class identifier • 1 — [1] all classes Default: 0 Class Identifier [number] Default: 0 Vectorised class as... [selection] Options: • 0 — [0] one single (multi-)polygon object • 1 — [1] each island as separated polygon Default: 0 Outputs Polygons [vector] Console usage processing.runalg(’saga:vectorisinggridclasses’, grid, class_all, class_id, split, polygons) See also . 18.7.15 Shapes lines Convert points to line(s) Description Converts points to lines. 18.7. SAGA algorithm provider 525 QGIS User Guide, Release 2.6 Parameters Points [vector: point] Points to convert. Order by... [tablefield: any] Lines will be ordered following this field. Separate by... [tablefield: any] Lines will be grouped according to this field. Outputs Lines [vector] The resulting layer. Console usage processing.runalg(’saga:convertpointstolines’, points, order, separate, lines) See also Convert polygons to lines Description Creates lines from polygons. Parameters Polygons [vector: polygon] Layer to process. Outputs Lines [vector] The resulting layer. Console usage processing.runalg(’saga:convertpolygonstolines’, polygons, lines) See also Line dissolve Description Parameters Lines [vector: any] 1. Attribute [tablefield: any] 2. Attribute [tablefield: any] 526 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 3. Attribute [tablefield: any] Dissolve... [selection] Options: • 0 — [0] lines with same attribute value(s) • 1 — [1] all lines Default: 0 Outputs Dissolved Lines [vector] Console usage processing.runalg(’saga:linedissolve’, lines, field_1, field_2, field_3, all, dissolved) See also Line-polygon intersection Description Parameters Lines [vector: line] Polygons [vector: polygon] Output [selection] Options: • 0 — [0] one multi-line per polygon • 1 — [1] keep original line attributes Default: 0 Outputs Intersection [vector] Console usage processing.runalg(’saga:linepolygonintersection’, lines, polygons, method, intersect) 18.7. SAGA algorithm provider 527 QGIS User Guide, Release 2.6 See also Line properties Description Calculates some information on each line of the layer. Parameters Lines [vector: line] Layer to analyze. Number of Parts [boolean] Determites whether to calculate number of segments in line. Default: True Number of Vertices [boolean] Determites whether to calculate number of vertices in line. Default: True Length [boolean] Determites whether to calculate total line lenght. Default: True Outputs Lines with Property Attributes [vector] The resulting layer. Console usage processing.runalg(’saga:lineproperties’, lines, bparts, bpoints, blength, output) See also Line simplification Description Simplyfies the geometry of a lines layer. Parameters Lines [vector: line] Layer to process. Tolerance [number] Simplification tolerance. Default: 1.0 Outputs Simplified Lines [vector] The resulting layer. 528 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:linesimplification’, lines, tolerance, output) See also . 18.7.16 Shapes points Add coordinates to points Description Adds the X and Y coordinates of feature in the attribute table of input layer. Parameters Points [vector: point] Input layer. Outputs Output [vector] Resulting layer with the updated attribute table. Console usage processing.runalg(’saga:addcoordinatestopoints’, input, output) See also Add polygon attributes to points Description Adds the specified field of the polygons layer to the attribute table of the points layer. The new attributes added for each point depend on the value of the background polygon layer. Parameters Points [vector: point] Points layer. Polygons [vector: polygon] Background polygons layer. Attribute [tablefield: any] Attribute of the polygons layer that will be added to the points layer. Outputs Result [vector] The resulting layer. 18.7. SAGA algorithm provider 529 QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:addpolygonattributestopoints’, input, polygons, field, output) See also Aggregate point observations Description Parameters Reference Points [vector: any] ID [tablefield: any] Observations [table] X[tablefield: any] Y[tablefield: any] Track [tablefield: any] Date [tablefield: any] Time [tablefield: any] Parameter [tablefield: any] Maximum Time Span (Seconds) [number] Default: 60.0 Maximum Distance [number] Default: 0.002 Outputs Aggregated [table] Console usage processing.runalg(’saga:aggregatepointobservations’, reference, reference_id, observations, x, y, track, date, time, parameter, eps_time, eps_space, aggregated) See also Clip points with polygons Description 530 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Points [vector: point] Polygons [vector: polygon] Add Attribute to Clipped Points [tablefield: any] Clipping Options [selection] Options: • 0 — [0] one layer for all points • 1 — [1] separate layer for each polygon Default: 0 Outputs Clipped Points [vector] Console usage processing.runalg(’saga:clippointswithpolygons’, points, polygons, field, method, clips) See also Convert lines to points Description Converts lines layer into a points. Parameters Lines [vector: line] Lines layer to convert. Insert Additional Points [boolean] Determines whether to add additional nodes or not. Default: True Insert Distance [number] Distance between the additional points. Default: 1.0 Outputs Points [vector] The resulting layer. Console usage processing.runalg(’saga:convertlinestopoints’, lines, add, dist, points) 18.7. SAGA algorithm provider 531 QGIS User Guide, Release 2.6 See also Convert multipoints to points Description Parameters Multipoints [vector: point] Outputs Points [vector] Console usage processing.runalg(’saga:convertmultipointstopoints’, multipoints, points) See also Convex hull Description Parameters Points [vector: point] Hull Construction [selection] Options: • 0 — [0] one hull for all shapes • 1 — [1] one hull per shape • 2 — [2] one hull per shape part Default: 0 Outputs Convex Hull [vector] Minimum Bounding Box [vector] Console usage 532 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 processing.runalg(’saga:convexhull’, shapes, polypoints, hulls, boxes) See also Distance matrix Description Generates a distance matrix between each point of the input layer. A unique ID will be created in the first row of the resulting matrix (symmetric matrix), while every other cell reflects the distance between the points. Parameters Points [vector: point] Input layer. Outputs Distance Matrix Table [table] The resulting table. Console usage processing.runalg(’saga:distancematrix’, points, table) See also Fit n points to shape Description Parameters Shapes [vector: polygon] Number of points [number] Default: 10 Outputs Points [vector] Console usage processing.runalg(’saga:fitnpointstoshape’, shapes, numpoints, points) 18.7. SAGA algorithm provider 533 QGIS User Guide, Release 2.6 See also Points filter Description Parameters Points [vector: point] Attribute [tablefield: any] Radius [number] Default: 1 Minimum Number of Points [number] Default: 0 Maximum Number of Points [number] Default: 0 Quadrants [boolean] Default: True Filter Criterion [selection] Options: • 0 — [0] keep maxima (with tolerance) • 1 — [1] keep minima (with tolerance) • 2 — [2] remove maxima (with tolerance) • 3 — [3] remove minima (with tolerance) • 4 — [4] remove below percentile • 5 — [5] remove above percentile Default: 0 Tolerance [number] Default: 0.0 Percentile [number] Default: 50 Outputs Filtered Points [vector] Console usage processing.runalg(’saga:pointsfilter’, points, field, radius, minnum, maxnum, quadrants, method, tolerance, percent, filter) 534 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Points thinning Description Parameters Points [vector: point] Attribute [tablefield: any] Resolution [number] Default: 1.0 Outputs Thinned Points [vector] Console usage processing.runalg(’saga:pointsthinning’, points, field, resolution, thinned) See also Remove duplicate points Description Parameters Points [vector: any] Attribute [tablefield: any] Point to Keep [selection] Options: • 0 — [0] first point • 1 — [1] last point • 2 — [2] point with minimum attribute value • 3 — [3] point with maximum attribute value Default: 0 Numeric Attribute Values [selection] Options: • 0 — [0] take value from the point to be kept 18.7. SAGA algorithm provider 535 QGIS User Guide, Release 2.6 • 1 — [1] minimum value of all duplicates • 2 — [2] maximum value of all duplicates • 3 — [3] mean value of all duplicates Default: 0 Outputs Result [vector] Console usage processing.runalg(’saga:removeduplicatepoints’, points, field, method, numeric, result) See also Separate points by direction Description Parameters Points [vector: point] Number of Directions [number] Default: 4 Tolerance (Degree) [number] Default: 5 Outputs Ouput [vector] Console usage processing.runalg(’saga:separatepointsbydirection’, points, directions, tolerance, output) See also . 536 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 18.7.17 Shapes polygons Convert lines to polygons Description Converts lines to polygons. Parameters Lines [vector: line] Lines to convert. Outputs Polygons [vector] The resulting layer. Console usage processing.runalg(’saga:convertlinestopolygons’, lines, polygons) See also Convert polygon/line vertices to points Description Converts the line or polygon vertices into points. Parameters Shapes [vector: any] Layer to process. Outputs Points [vector] The resulting layer. Console usage processing.runalg(’saga:convertpolygonlineverticestopoints’, shapes, points) See also Polygon centroids Description Calculates the centroids of polygons. 18.7. SAGA algorithm provider 537 QGIS User Guide, Release 2.6 Parameters Polygons [vector: polygon] Input layer. Centroids for each part [boolean] Determites whether centroids should be calculated for each part of multipart polygon or not. Default: True Outputs Centroids [vector] The resulting layer. Console usage processing.runalg(’saga:polygoncentroids’, polygons, method, centroids) See also Polygon dissolve Description Parameters Polygons [vector: polygon] 1. Attribute [tablefield: any] Optional. 2. Attribute [tablefield: any] Optional. 3. Attribute [tablefield: any] Optional. Dissolve... [selection] Options: • 0 — [0] polygons with same attribute value • 1 — [1] all polygons • 2 — [2] polygons with same attribute value (keep inner boundaries) • 3 — [3] all polygons (keep inner boundaries) Default: 0 Outputs Dissolved Polygons [vector] 538 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:polygondissolve’, polygons, field_1, field_2, field_3, dissolve, dissolved) See also Polygon-line intersection Description Parameters Polygons [vector: polygon] Lines [vector: line] Outputs Intersection [vector] Console usage processing.runalg(’saga:polygonlineintersection’, polygons, lines, intersect) See also Polygon parts to separate polygons Description Parameters Polygons [vector: polygon] Ignore Lakes [boolean] Default: True Outputs Polygon Parts [vector] Console usage processing.runalg(’saga:polygonpartstoseparatepolygons’, polygons, lakes, parts) 18.7. SAGA algorithm provider 539 QGIS User Guide, Release 2.6 See also Polygon properties Description Parameters Polygons [vector: polygon] Number of Parts [boolean] Default: True Number of Vertices [boolean] Default: True Perimeter [boolean] Default: True Area [boolean] Default: True Outputs Polygons with Property Attributes [vector] Console usage processing.runalg(’saga:polygonproperties’, polygons, bparts, bpoints, blength, barea, output) See also Polygon shape indices Description Calculates spatial statistics for polygons. This includes: • area • perimeter • perimeter / area • perimeter / square root of the area • maximum distance • maximum distance / area • maximum distance / square root of the area • shape index 540 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Shapes [vector: polygon] Layer to analyze. Outputs Shape Index [vector] The resulting layer. Console usage processing.runalg(’saga:polygonshapeindices’, shapes, index) See also Polygons to edges and nodes Description Extracts boundaries and nodes of polygons in separate files. Parameters Polygons [vector: polygon] Input layer. Outputs Edges [vector] Resulting line layer with polygons boundaries. Nodes [vector] Resulting line layer with polygons nodes. Console usage processing.runalg(’saga:polygonstoedgesandnodes’, polygons, edges, nodes) See also . 18.7.18 Shapes tools Create graticule Description Creates a grid. 18.7. SAGA algorithm provider 541 QGIS User Guide, Release 2.6 Parameters Extent [vector: any] Optional. Grid will be created according to the selected layer. Output extent [extent] Extent of the grid. Default: 0,1,0,1 Division Width [number] X-axes spacing between the lines. Default: 1.0 Division Height [number] Y-axes spacing between the lines. Default: 1.0 Type [selection] Geometry type of the resulting grid. Options: • 0 — [0] Lines • 1 — [1] Rectangles Default: 0 Outputs Graticule [vector] The resulting layer. Console usage processing.runalg(’saga:creategraticule’, extent, output_extent, distx, disty, type, graticule) See also Cut shapes layer Description Parameters Vector layer to cut [vector: any] Method [selection] Options: • 0 — [0] completely contained • 1 — [1] intersects • 2 — [2] center Default: 0 Cutting polygons [vector: any] 542 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Result [vector] Extent [vector] Console usage processing.runalg(’saga:cutshapeslayer’, shapes, method, polygons_polygons, cut, extent) See also Get shapes extents Description Creates polygons according to the extent of the input layer features. Parameters Shapes [vector: any] Input layer. Parts [boolean] Determines whether create polygon for each feature (True) or just create single polygon for whole layer (False). Default: True Outputs Extents [vector] The resulting layer. Console usage processing.runalg(’saga:getshapesextents’, shapes, parts, extents) See also Merge shapes layers Description Merges two or more input layer into a unique resulting layer. You can merge together only layer of the same type (polygons with polygons, lines with lines, points with points). The attribute table of the resulting layer will include only the attributes of the first input layer. Two additional columns will be added: one corresponding to the ID of every merged layer and the other one corresponding to the original name of the merged layer. 18.7. SAGA algorithm provider 543 QGIS User Guide, Release 2.6 Parameters Main Layer [vector: any] Initial layer. Additional Layers [multipleinput: any vectors] Optional. Layer(s) to merge with. Outputs Merged Layer [vector] The resulting layer. Console usage processing.runalg(’saga:mergeshapeslayers’, main, layers, out) See also Polar to cartesian coordinates Description Parameters Polar Coordinates [vector: any] Exaggeration [tablefield: any] Exaggeration Factor [number] Default: 1 Radius [number] Default: 6371000.0 Degree [boolean] Default: True Outputs Cartesian Coordinates [vector] Console usage processing.runalg(’saga:polartocartesiancoordinates’, polar, f_exagg, d_exagg, radius, degree, cartes) 544 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Quadtree structure to shapes Description Parameters Shapes [vector: any] Attribute [tablefield: any] Outputs Polygons [vector] Lines [vector] Duplicated Points [vector] Console usage processing.runalg(’saga:quadtreestructuretoshapes’, shapes, attribute, polygons, lines, points) See also Shapes buffer Description Creates buffer around features based on fixed distance or distance field. Parameters Shapes [vector: any] Input layer. Buffer Distance [selection] Buffering method. Options: • 0 — [0] fixed value • 1 — [1] attribute field Default: 0 Buffer Distance (Fixed) [number] Buffer distance for “fixed value” method. Default: 100.0 Buffer Distance (Attribute) [tablefield: any] Name of the distance field for “attribute field” method. Scaling Factor for Attribute Value [number] Default: 1.0 18.7. SAGA algorithm provider 545 QGIS User Guide, Release 2.6 Number of Buffer Zones [number] Number of buffer(s) to generate. Default: 1.0 Circle Point Distance [Degree] [number] Smoothness of the buffer borders: great numbers means rough borders. Default: 5.0 Dissolve Buffers [boolean] Determines whether to dissolve results or not. Default: True Outputs Buffer [vector] The resulting layer. Console usage processing.runalg(’saga:shapesbuffer’, shapes, buf_type, buf_dist, buf_field, buf_scale, buf_zones, dcircle, dissolve, buffer) See also Split shapes layer randomly Description Splits the input layer randomly in two parts. Parameters Shapes [vector: any] Layer to split. Split ratio (%) [number] Split ratio between the resulting layers. Default: 50 Outputs Group A [vector] First resulting layer. Group B [vector] Second resulting layer. Console usage processing.runalg(’saga:splitshapeslayerrandomly’, shapes, percent, a, b) See also Transform shapes Description 546 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Shapes [vector: any] dX [number] Default: 0.0 dY [number] Default: 0.0 Angle [number] Default: 0.0 Scale Factor X [number] Default: 1.0 Scale Factor Y [number] Default: 1.0 X[number] Default: 0.0 Y[number] Default: 0.0 Outputs Output [vector] Console usage processing.runalg(’saga:transformshapes’, in, dx, dy, angle, scalex, scaley, anchorx, anchory, out) See also . 18.7.19 Shapes transect Transect through polygon shapefile Description Parameters Line Transect(s) [vector: line] Theme [vector: any] Theme Field [tablefield: any] 18.7. SAGA algorithm provider 547 QGIS User Guide, Release 2.6 Outputs Result table [table] Console usage processing.runalg(’saga:transectthroughpolygonshapefile’, transect, theme, theme_field, transect_result) See also . 18.7.20 Simulation fire Fire risk analysis Description Parameters DEM [raster] Fuel Model [raster] Wind Speed [raster] Wind Direction [raster] Dead Fuel Moisture 1H [raster] Dead Fuel Moisture 10H [raster] Dead Fuel Moisture 100H [raster] Herbaceous Fuel Moisture [raster] Wood Fuel Moisture [raster] Value [raster] Optional. Base Probability [raster] Optional. Number of Events [number] Default: 1000 Fire Length [number] Default: 100 548 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Danger [raster] Compound Probability [raster] Priority Index [raster] Console usage processing.runalg(’saga:fireriskanalysis’, dem, fuel, windspd, winddir, m1h, m10h, m100h, mherb, mwood, value, baseprob, montecarlo, interval, danger, compprob, priority) See also Simulation Description Parameters DEM [raster] Fuel Model [raster] Wind Speed [raster] Wind Direction [raster] Dead Fuel Moisture 1H [raster] Dead Fuel Moisture 10H [raster] Dead Fuel Moisture 100H [raster] Herbaceous Fuel Moisture [raster] Wood Fuel Moisture [raster] Ignition Points [raster] Update View [boolean] Default: True Outputs Time [raster] Flame Length [raster] Intensity [raster] Console usage processing.runalg(’saga:simulation’, dem, fuel, windspd, winddir, m1h, m10h, m100h, mherb, mwood, ignition, updateview, time, flame, intensity) 18.7. SAGA algorithm provider 549 QGIS User Guide, Release 2.6 See also . 18.7.21 Simulation hydrology Overland flow - kinematic wave d8 Description Parameters Elevation [raster] Gauges [vector: any] Optional. Simulation Time [h] [number] Default: 24 Simulation Time Step [h] [number] Default: 0.1 Manning’s Roughness [number] Default: 0.03 Max. Iterations [number] Default: 100 Epsilon [number] Default: 0.0001 Precipitation [selection] Options: • 0 — [0] Homogenous • 1 — [1] Above Elevation • 2 — [2] Left Half Default: 0 Threshold Elevation [number] Default: 0.0 Outputs Runoff [raster] Flow at Gauges [table] 550 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:overlandflowkinematicwaved8’, dem, gauges, time_span, time_step, roughness, newton_maxiter, newton_epsilon, precip, threshold, flow, gauges_flow) See also Water retention capacity Description Parameters Plot Holes [vector: any] DEM [raster] Outputs Final Parameters [vector] Water Retention Capacity [raster] Console usage processing.runalg(’saga:waterretentioncapacity’, shapes, dem, output, retention) See also . 18.7.22 Table calculus Fill gaps in records Description Parameters Table [table] Order [tablefield: any] Interpolation [selection] Options: • 0 — [0] Nearest Neighbour • 1 — [1] Linear 18.7. SAGA algorithm provider 551 QGIS User Guide, Release 2.6 • 2 — [2] Spline Default: 0 Outputs Table without Gaps [table] Console usage processing.runalg(’saga:fillgapsinrecords’, table, order, method, nogaps) See also Principle components analysis Description Parameters Table [table] Method [selection] Options: • 0 — [0] correlation matrix • 1 — [1] variance-covariance matrix • 2 — [2] sums-of-squares-and-cross-products matrix Default: 0 Number of Components [number] Default: 3 Outputs Principle Components [table] Console usage processing.runalg(’saga:principlecomponentsanalysis’, table, method, nfirst, pca) See also Running average Description 552 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Input [table] Attribute [tablefield: any] Number of Records [number] Default: 10 Outputs Output [table] Console usage processing.runalg(’saga:runningaverage’, input, field, count, output) See also . 18.7.23 Table tools Change date format Description Converts the date format of the input layer. Parameters Table [table] Input table. Date Field [tablefield: any] Attribute the date. Input Format [selection] Input date format. Options: • 0 — [0] dd.mm.yy • 1 — [1] yy.mm.dd • 2 — [2] dd:mm:yy • 3 — [3] yy:mm:dd • 4 — [4] ddmmyyyy, fix size • 5 — [5] yyyymmdd, fix size • 6 — [6] ddmmyy, fix size • 7 — [7] yymmdd, fix size • 8 — [8] Julian Day Default: 0 18.7. SAGA algorithm provider 553 QGIS User Guide, Release 2.6 Output Format [selection] Output date format. Options: • 0 — [0] dd.mm.yy • 1 — [1] yy.mm.dd • 2 — [2] dd:mm:yy • 3 — [3] yy:mm:dd • 4 — [4] ddmmyyyy, fix size • 5 — [5] yyyymmdd, fix size • 6 — [6] ddmmyy, fix size • 7 — [7] yymmdd, fix size • 8 — [8] Julian Day Default: 0 Outputs Output [table] The resulting table. Console usage processing.runalg(’saga:changedateformat’, table, field, fmt_in, fmt_out, output) See also Change time format Description Converts the time format of the input layer. Parameters Table [table] Input table. Time Field [tablefield: any] Attribute with time. Input Format [selection] Input time format. Options: • 0 — [0] hh.mm.ss • 1 — [1] hh:mm:ss • 2 — [2] hhmmss, fix size • 3 — [3] hours • 4 — [4] minutes • 5 — [5] seconds Default: 0 554 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Output Format [selection] Output time format. Options: • 0 — [0] hh.mm.ss • 1 — [1] hh:mm:ss • 2 — [2] hhmmss, fix size • 3 — [3] hours • 4 — [4] minutes • 5 — [5] seconds Default: 0 Outputs Output [table] The resulting table. Console usage processing.runalg(’saga:changetimeformat’, table, field, fmt_in, fmt_out, output) See also . 18.7.24 Terrain channels Channel network and drainage basins Description Parameters Elevation [raster] Threshold [number] Default: 5.0 Outputs Flow Direction [raster] Flow Connectivity [raster] Strahler Order [raster] Drainage Basins [raster] Channels [vector] Drainage Basins [vector] 18.7. SAGA algorithm provider 555 QGIS User Guide, Release 2.6 Junctions [vector] Console usage processing.runalg(’saga:channelnetworkanddrainagebasins’, dem, threshold, direction, connection, order, basin, segments, basins, nodes) See also Channel network Description Parameters Elevation [raster] Flow Direction [raster] Optional. Initiation Grid [raster] Initiation Type [selection] Options: • 0 — [0] Less than • 1 — [1] Equals • 2 — [2] Greater than Default: 0 Initiation Threshold [number] Default: 0.0 Divergence [raster] Optional. Tracing: Max. Divergence [number] Default: 10 Tracing: Weight [raster] Optional. Min. Segment Length [number] Default: 10 Outputs Channel Network [raster] Channel Direction [raster] Channel Network [vector] 556 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:channelnetwork’, elevation, sinkroute, init_grid, init_method, init_value, div_grid, div_cells, trace_weight, minlen, chnlntwrk, chnlroute, shapes) See also Overland flow distance to channel network Description Parameters Elevation [raster] Channel Network [raster] Flow Algorithm [selection] Options: • 0 — [0] D8 • 1 — [1] MFD Default: 0 Outputs Overland Flow Distance [raster] Vertical Overland Flow Distance [raster] Horizontal Overland Flow Distance [raster] Console usage processing.runalg(’saga:overlandflowdistancetochannelnetwork’, elevation, channels, method, distance, distvert, disthorz) See also Strahler order Description Parameters Elevation [raster] 18.7. SAGA algorithm provider 557 QGIS User Guide, Release 2.6 Outputs Strahler Order [raster] Console usage processing.runalg(’saga:strahlerorder’, dem, strahler) See also Vertical distance to channel network Description Parameters Elevation [raster] Channel Network [raster] Tension Threshold [Percentage of Cell Size] [number] Default: 1 Keep Base Level below Surface [boolean] Default: True Outputs Vertical Distance to Channel Network [raster] Channel Network Base Level [raster] Console usage processing.runalg(’saga:verticaldistancetochannelnetwork’, elevation, channels, threshold, nounderground, distance, baselevel) See also Watershed basins Description 558 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Elevation [raster] Channel Network [raster] Sink Route [raster] Optional. Min. Size [number] Default: 0 Outputs Watershed Basins [raster] Console usage processing.runalg(’saga:watershedbasins’, elevation, channels, sinkroute, minsize, basins) See also . 18.7.25 Terrain hydrology Burn stream network into dem Description Parameters DEM [raster] Streams [raster] Method [selection] Options: • 0 — [0] simply decrease cell’s value by epsilon • 1 — [1] lower cell’s value to neighbours minimum value minus epsilon Default: 0 Epsilon [number] Default: 1.0 Outputs Processed DEM [raster] 18.7. SAGA algorithm provider 559 QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:burnstreamnetworkintodem’, dem, stream, method, epsilon, burn) See also Catchment area (flow tracing) Description Parameters Elevation [raster] Sink Routes [raster] Optional. Weight [raster] Optional. Material [raster] Optional. Target [raster] Optional. Step [number] Default: 1 Method [selection] Options: • 0 — [0] Rho 8 • 1 — [1] Kinematic Routing Algorithm • 2 — [2] DEMON Default: 0 DEMON - Min. DQV [number] Default: 0.0 Flow Correction [boolean] Default: True Outputs Catchment Area [raster] Catchment Height [raster] Catchment Slope [raster] Total accumulated Material [raster] 560 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Accumulated Material from _left_ side [raster] Accumulated Material from _right_ side [raster] Console usage processing.runalg(’saga:catchmentareaflowtracing’, elevation, sinkroute, weight, material, target, step, method, mindqv, correct, carea, cheight, cslope, accu_tot, accu_left, accu_right) See also Catchment area (recursive) Description Parameters Elevation [raster] Sink Routes [raster] Optional. Weight [raster] Optional. Material [raster] Optional. Target [raster] Optional. Step [number] Default: 1 Target Areas [raster] Optional. Method [selection] Options: • 0 — [0] Deterministic 8 • 1 — [1] Rho 8 • 2 — [2] Deterministic Infinity • 3 — [3] Multiple Flow Direction Default: 0 Convergence [number] Default: 1.1 18.7. SAGA algorithm provider 561 QGIS User Guide, Release 2.6 Outputs Catchment Area [raster] Catchment Height [raster] Catchment Slope [raster] Total accumulated Material [raster] Accumulated Material from _left_ side [raster] Accumulated Material from _right_ side [raster] Flow Path Length [raster] Console usage processing.runalg(’saga:catchmentarearecursive’, elevation, sinkroute, weight, material, target, step, targets, method, convergence, carea, cheight, cslope, accu_tot, accu_left, accu_right, flowlen) See also Catchment Area Description Parameters Elevation [raster] Method [selection] Options: • 0 — [0] Deterministic 8 • 1 — [1] Rho 8 • 2 — [2] Braunschweiger Reliefmodell • 3 — [3] Deterministic Infinity • 4 — [4] Multiple Flow Direction • 5 — [5] Multiple Triangular Flow Directon Default: 0 Outputs Catchment Area [raster] Console usage processing.runalg(’saga:catchmentarea’, elevation, method, carea) 562 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Cell balance Description Parameters Elevation [raster] Parameter [raster] Optional. Default Weight [number] Default: 1.0 Method [selection] Options: • 0 — [0] Deterministic 8 • 1 — [1] Multiple Flow Direction Default: 0 Outputs Cell Balance [raster] Console usage processing.runalg(’saga:cellbalance’, dem, weights, weight, method, balance) See also Edge contamination Description Parameters Elevation [raster] Outputs Edge Contamination [raster] 18.7. SAGA algorithm provider 563 QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:edgecontamination’, dem, contamination) See also Fill Sinks Description Parameters DEM [raster] Minimum Slope [Degree] [number] Default: 0.01 Outputs Filled DEM [raster] Console usage processing.runalg(’saga:fillsinks’, dem, minslope, result) See also Fill sinks (wang & liu) Description Parameters DEM [raster] Minimum Slope [Degree] [number] Default: 0.01 Outputs Filled DEM [raster] Flow Directions [raster] Watershed Basins [raster] 564 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:fillsinkswangliu’, elev, minslope, filled, fdir, wshed) See also Fill sinks xxl (wang & liu) Description Parameters DEM [raster] Minimum Slope [Degree] [number] Default: 0.01 Outputs Filled DEM [raster] Console usage processing.runalg(’saga:fillsinksxxlwangliu’, elev, minslope, filled) See also Flat detection Description Parameters DEM [raster] Flat Area Values [selection] Options: • 0 — [0] elevation • 1 — [1] enumeration Default: 0 18.7. SAGA algorithm provider 565 QGIS User Guide, Release 2.6 Outputs No Flats [raster] Flat Areas [raster] Console usage processing.runalg(’saga:flatdetection’, dem, flat_output, noflats, flats) See also Flow path length Description Parameters Elevation [raster] Seeds [raster] Optional. Seeds Only [boolean] Default: True Flow Routing Algorithm [selection] Options: • 0 — [0] Deterministic 8 (D8) • 1 — [1] Multiple Flow Direction (FD8) Default: 0 Convergence (FD8) [number] Default: 1.1 Outputs Flow Path Length [raster] Console usage processing.runalg(’saga:flowpathlength’, elevation, seed, seeds_only, method, convergence, length) 566 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Flow width and specific catchment area Description Parameters Elevation [raster] Total Catchment Area (TCA) [raster] Optional. Method [selection] Options: • 0 — [0] Deterministic 8 • 1 — [1] Multiple Flow Direction (Quinn et al. 1991) • 2 — [2] Aspect Default: 0 Outputs Flow Width [raster] Specific Catchment Area (SCA) [raster] Console usage processing.runalg(’saga:flowwidthandspecificcatchmentarea’, dem, tca, method, width, sca) See also Lake flood Description Parameters DEM [raster] Seeds [raster] Absolute Water Levels [boolean] Default: True 18.7. SAGA algorithm provider 567 QGIS User Guide, Release 2.6 Outputs Lake [raster] Surface [raster] Console usage processing.runalg(’saga:lakeflood’, elev, seeds, level, outdepth, outlevel) See also Ls factor Description Parameters Slope [raster] Catchment Area [raster] Area to Length Conversion [selection] Options: • 0 — [0] no conversion (areas already given as specific catchment area) • 1 — [1] 1 / cell size (specific catchment area) • 2 — [2] square root (catchment length) Default: 0 Method (LS) [selection] Options: • 0 — [0] Moore et al. 1991 • 1 — [1] Desmet & Govers 1996 • 2 — [2] Boehner & Selige 2006 Default: 0 Rill/Interrill Erosivity [number] Default: 0.0 Stability [selection] Options: • 0 — [0] stable • 1 — [1] instable (thawing) Default: 0 568 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs LS Factor [raster] Console usage processing.runalg(’saga:lsfactor’, slope, area, conv, method, erosivity, stability, ls) See also Saga wetness index Description Parameters Elevation [raster] t [number] Default: 10 Outputs Catchment area [raster] Catchment slope [raster] Modified catchment area [raster] Wetness index [raster] Console usage processing.runalg(’saga:sagawetnessindex’, dem, t, c, gn, cs, sb) See also Sink drainage route detection Description Parameters Elevation [raster] Threshold [boolean] Default: True 18.7. SAGA algorithm provider 569 QGIS User Guide, Release 2.6 Threshold Height [number] Default: 100.0 Outputs Sink Route [raster] Console usage processing.runalg(’saga:sinkdrainageroutedetection’, elevation, threshold, thrsheight, sinkroute) See also Sink removal Description Parameters DEM [raster] Sink Route [raster] Optional. Method [selection] Options: • 0 — [0] Deepen Drainage Routes • 1 — [1] Fill Sinks Default: 0 Threshold [boolean] Default: True Threshold Height [number] Default: 100.0 Outputs Preprocessed DEM [raster] Console usage processing.runalg(’saga:sinkremoval’, dem, sinkroute, method, threshold, thrsheight, dem_preproc) 570 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Slope length Description Parameters Elevation [raster] Outputs Slope Length [raster] Console usage processing.runalg(’saga:slopelength’, dem, length) See also Stream power index Description Parameters Slope [raster] Catchment Area [raster] Area Conversion [selection] Options: • 0 — [0] no conversion (areas already given as specific catchment area) • 1 — [1] 1 / cell size (pseudo specific catchment area) Default: 0 Outputs Stream Power Index [raster] Console usage processing.runalg(’saga:streampowerindex’, slope, area, conv, spi) 18.7. SAGA algorithm provider 571 QGIS User Guide, Release 2.6 See also Topographic wetness index (twi) Description Parameters Slope [raster] Catchment Area [raster] Transmissivity [raster] Optional. Area Conversion [selection] Options: • 0 — [0] no conversion (areas already given as specific catchment area) • 1 — [1] 1 / cell size (pseudo specific catchment area) Default: 0 Method (TWI) [selection] Options: • 0 — [0] Standard • 1 — [1] TOPMODEL Default: 0 Outputs Topographic Wetness Index [raster] Console usage processing.runalg(’saga:topographicwetnessindextwi’, slope, area, trans, conv, method, twi) See also Upslope Area Description 572 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Target Area [raster] Optional. Target X coordinate [number] Default: 0.0 Target Y coordinate [number] Default: 0.0 Elevation [raster] Sink Routes [raster] Optional. Method [selection] Options: • 0 — [0] Deterministic 8 • 1 — [1] Deterministic Infinity • 2 — [2] Multiple Flow Direction Default: 0 Convergence [number] Default: 1.1 Outputs Upslope Area [raster] Console usage processing.runalg(’saga:upslopearea’, target, target_pt_x, target_pt_y, elevation, sinkroute, method, converge, area) See also . 18.7.26 Terrain lighting Analytical hillshading Description 18.7. SAGA algorithm provider 573 QGIS User Guide, Release 2.6 Parameters Elevation [raster] Shading Method [selection] Options: • 0 — [0] Standard • 1 — [1] Standard (max. 90Degree) • 2 — [2] Combined Shading • 3 — [3] Ray Tracing Default: 0 Azimuth [Degree] [number] Default: 315.0 Declination [Degree] [number] Default: 45.0 Exaggeration [number] Default: 4.0 Outputs Analytical Hillshading [raster] Console usage processing.runalg(’saga:analyticalhillshading’, elevation, method, azimuth, declination, exaggeration, shade) See also Sky view factor Description Parameters Elevation [raster] Maximum Search Radius [number] Default: 10000 Method [selection] Options: • 0 — [0] multi scale • 1 — [1] sectors Default: 0 574 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Multi Scale Factor [number] Default: 3 Number of Sectors [number] Default: 8 Outputs Visible Sky [raster] Sky View Factor [raster] Sky View Factor (Simplified) [raster] Terrain View Factor [raster] Console usage processing.runalg(’saga:skyviewfactor’, dem, maxradius, method, level_inc, ndirs, visible, svf, simple, terrain) See also Topographic correction Description Parameters Elevation [raster] Original Image [raster] Azimuth [number] Default: 180.0 Height [number] Default: 45.0 Method [selection] Options: • 0 — [0] Cosine Correction (Teillet et al. 1982) • 1 — [1] Cosine Correction (Civco 1989) • 2 — [2] Minnaert Correction • 3 — [3] Minnaert Correction with Slope (Riano et al. 2003) • 4 — [4] Minnaert Correction with Slope (Law & Nichol 2004) • 5 — [5] C Correction • 6 — [6] Normalization (after Civco, modified by Law & Nichol) Default: 0 18.7. SAGA algorithm provider 575 QGIS User Guide, Release 2.6 Minnaert Correction [number] Default: 0.5 Maximum Cells (C Correction Analysis) [number] Default: 1000 Value Range [selection] Options: • 0 — [0] 1 byte (0-255) • 1 — [1] 2 byte (0-65535) Default: 0 Outputs Corrected Image [raster] Console usage processing.runalg(’saga:topographiccorrection’, dem, original, azi, hgt, method, minnaert, maxcells, maxvalue, corrected) See also . 18.7.27 Terrain morphometry Convergence index Description Calculates an index of convergence/divergence regarding to overland flow. By its meaning it is similar to plan or horizontal curvature, but gives much smoother results. The calculation uses the aspects of surrounding cells, i.e. it looks to which degree surrounding cells point to the center cell. The result is given as percentages, negative values correspond to convergent, positive to divergent flow conditions. Minus 100 would be like a peak of a cone, plus 100 a pit, and 0 an even slope. Parameters Elevation [raster] Method [selection] Options: • 0 — [0] Aspect • 1 — [1] Gradient Default: 0 Gradient Calculation [selection] Options: • 0 — [0] 2 x 2 576 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 1 — [1] 3 x 3 Default: 0 Outputs Convergence Index [raster] Console usage processing.runalg(’saga:convergenceindex’, elevation, method, neighbours, result) See also • Koethe, R. / Lehmeier, F. (1996): ‘SARA, System zur Automatischen Relief-Analyse’, Benutzerhandbuch, 2. Auflage [Geogr. Inst. Univ. Goettingen, unpublished] Convergence index (search radius) Description Parameters Elevation [raster] Radius [Cells] [number] Default: 10 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1 Gradient [boolean] Default: True 18.7. SAGA algorithm provider 577 QGIS User Guide, Release 2.6 Difference [selection] Options: • 0 — [0] direction to the center cell • 1 — [1] center cell’s aspect direction Default: 0 Outputs Convergence Index [raster] Console usage processing.runalg(’saga:convergenceindexsearchradius’, elevation, radius, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, slope, difference, convergence) See also Curvature classification Description Parameters Plan Curvature [raster] Profile Curvature [raster] Threshold for plane [number] Default: 0.001 Outputs Curvature Classification [raster] Console usage processing.runalg(’saga:curvatureclassification’, cplan, cprof, threshold, class) See also Diurnal anisotropic heating Description 578 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Elevation [raster] Alpha Max (Degree) [number] Default: 202.5 Outputs Diurnal Anisotropic Heating [raster] Console usage processing.runalg(’saga:diurnalanisotropicheating’, dem, alpha_max, dah) See also Downslope distance gradient Description Parameters Elevation [raster] Vertical Distance [number] Default: 10 Output [selection] Options: • 0 — [0] distance • 1 — [1] gradient (tangens) • 2 — [2] gradient (degree) Default: 0 Outputs Gradient [raster] Gradient Difference [raster] Console usage processing.runalg(’saga:downslopedistancegradient’, dem, distance, output, gradient, difference) 18.7. SAGA algorithm provider 579 QGIS User Guide, Release 2.6 See also Effective air flow heights Description Parameters Elevation [raster] Wind Direction [raster] Optional. Wind Speed [raster] Optional. Constant Wind Direction [Degree] [number] Default: 135 Old Version [boolean] Default: True Search Distance [km] [number] Default: 300 Acceleration [number] Default: 1.5 Use Pyramids with New Version [boolean] Default: True Lee Factor [number] Default: 0.5 Luv Factor [number] Default: 1.0 Wind Direction Units [selection] Options: • 0 — [0] radians • 1 — [1] degree Default: 0 Wind Speed Scale Factor [number] Default: 1.0 Outputs Effective Air Flow Heights [raster] 580 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:effectiveairflowheights’, dem, dir, len, dir_const, oldver, maxdist, accel, pyramids, leefact, luvfact, dir_units, len_scale, afh) See also Hypsometry Description Parameters Elevation [raster] Number of Classes [number] Default: 100.0 Sort [selection] Options: • 0 — [0] up • 1 — [1] down Default: 0 Classification Constant [selection] Options: • 0 — [0] height • 1 — [1] area Default: 0 Use Z-Range [boolean] Default: True Z-Range Min [number] Default: 0.0 Z-Range Max [number] Default: 1000.0 Outputs Hypsometry [table] Console usage processing.runalg(’saga:hypsometry’, elevation, count, sorting, method, bzrange, zrange_min, zrange_max, table) 18.7. SAGA algorithm provider 581 QGIS User Guide, Release 2.6 See also Land surface temperature Description Parameters Elevation [m] [raster] Short Wave Radiation [kW/m2] [raster] Leaf Area Index [raster] Elevation at Reference Station [m] [number] Default: 0.0 Temperature at Reference Station [Deg.Celsius] [number] Default: 0.0 Temperature Gradient [Deg.Celsius/km] [number] Default: 6.5 C Factor [number] Default: 1.0 Outputs Land Surface Temperature [Deg.Celsius] [raster] Console usage processing.runalg(’saga:landsurfacetemperature’, dem, swr, lai, z_reference, t_reference, t_gradient, c_factor, lst) See also Mass balance index Description Parameters Elevation [raster] Vertical Distance to Channel Network [raster] Optional. 582 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 T Slope [number] Default: 15.0 T Curvature [number] Default: 0.01 T Vertical Distance to Channel Network [number] Default: 15.0 Outputs Mass Balance Index [raster] Console usage processing.runalg(’saga:massbalanceindex’, dem, hrel, tslope, tcurve, threl, mbi) See also Morphometric protection index Description Parameters Elevation [raster] Radius [number] Default: 2000.0 Outputs Protection Index [raster] Console usage processing.runalg(’saga:morphometricprotectionindex’, dem, radius, protection) See also Multiresolution index of valley bottom flatness (mrvbf) Description 18.7. SAGA algorithm provider 583 QGIS User Guide, Release 2.6 Parameters Elevation [raster] Initial Threshold for Slope [number] Default: 16 Threshold for Elevation Percentile (Lowness) [number] Default: 0.4 Threshold for Elevation Percentile (Upness) [number] Default: 0.35 Shape Parameter for Slope [number] Default: 4.0 Shape Parameter for Elevation Percentile [number] Default: 3.0 Update Views [boolean] Default: True Classify [boolean] Default: True Maximum Resolution (Percentage) [number] Default: 100 Outputs MRVBF [raster] MRRTF [raster] Console usage processing.runalg(’saga:multiresolutionindexofvalleybottomflatnessmrvbf’, dem, t_slope, t_pctl_v, t_pctl_r, p_slope, p_pctl, update, classify, max_res, mrvbf, mrrtf) See also Real area calculation Description Parameters Elevation [raster] Outputs Real Area Grid [raster] 584 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:realareacalculation’, dem, area) See also Relative heights and slope positions Description Parameters Elevation [raster] w [number] Default: 0.5 t [number] Default: 10.0 e [number] Default: 2.0 Outputs Slope Height [raster] Valley Depth [raster] Normalized Height [raster] Standardized Height [raster] Mid-Slope Positon [raster] Console usage processing.runalg(’saga:relativeheightsandslopepositions’, dem, w, t, e, ho, hu, nh, sh, ms) See also Slope, aspect, curvature Description 18.7. SAGA algorithm provider 585 QGIS User Guide, Release 2.6 Parameters Elevation [raster] Method [selection] Options: • 0 — [0] Maximum Slope (Travis et al. 1975) • 1 — [1] Maximum Triangle Slope (Tarboton 1997) • 2 — [2] Least Squares Fitted Plane (Horn 1981, Costa-Cabral & Burgess 1996) • 3 — [3] Fit 2.Degree Polynom (Bauer, Rohdenburg, Bork 1985) • 4 — [4] Fit 2.Degree Polynom (Heerdegen & Beran 1982) • 5 — [5] Fit 2.Degree Polynom (Zevenbergen & Thorne 1987) • 6 — [6] Fit 3.Degree Polynom (Haralick 1983) Default: 5 Outputs Slope [raster] Aspect [raster] Curvature [raster] Plan Curvature [raster] Profile Curvature [raster] Console usage processing.runalg(’saga:slopeaspectcurvature’, elevation, method, slope, aspect, curv, hcurv, vcurv) See also Surface specific points Description Parameters Elevation [raster] Method [selection] Options: • 0 — [0] Mark Highest Neighbour • 1 — [1] Opposite Neighbours • 2 — [2] Flow Direction • 3 — [3] Flow Direction (up and down) 586 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 • 4 — [4] Peucker & Douglas Default: 0 Threshold [number] Default: 2.0 Outputs Result [raster] Console usage processing.runalg(’saga:surfacespecificpoints’, elevation, method, threshold, result) See also Terrain ruggedness index (tri) Description Parameters Elevation [raster] Radius (Cells) [number] Default: 1 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1.0 Outputs Terrain Ruggedness Index (TRI) [raster] 18.7. SAGA algorithm provider 587 QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:terrainruggednessindextri’, dem, radius, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, tri) See also Topographic position index (tpi) Description Parameters Elevation [raster] Standardize [boolean] Default: True Min Radius [number] Default: 0.0 Max Radius [number] Default: 100.0 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 75.0 Outputs Topographic Position Index [raster] Console usage processing.runalg(’saga:topographicpositionindextpi’, dem, standard, radius_min, radius_max, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, tpi) 588 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also Tpi based landform classification Description Parameters Elevation [raster] Min Radius A [number] Default: 0 Max Radius A [number] Default: 100 Min Radius B [number] Default: 0 Max Radius B [number] Default: 1000 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 75.0 Outputs Landforms [raster] Console usage processing.runalg(’saga:tpibasedlandformclassification’, dem, radius_a_min, radius_a_max, radius_b_min, radius_b_max, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, landforms) 18.7. SAGA algorithm provider 589 QGIS User Guide, Release 2.6 See also Vector ruggedness measure (vrm) Description Parameters Elevation [raster] Radius (Cells) [number] Default: 1 Distance Weighting [selection] Options: • 0 — [0] no distance weighting • 1 — [1] inverse distance to a power • 2 — [2] exponential • 3 — [3] gaussian weighting Default: 0 Inverse Distance Weighting Power [number] Default: 1 Inverse Distance Offset [boolean] Default: True Gaussian and Exponential Weighting Bandwidth [number] Default: 1 Outputs Vector Terrain Ruggedness (VRM) [raster] Console usage processing.runalg(’saga:vectorruggednessmeasurevrm’, dem, radius, distance_weighting_weighting, distance_weighting_idw_power, distance_weighting_idw_offset, distance_weighting_bandwidth, vrm) See also Wind effect Description 590 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Parameters Elevation [raster] Wind Direction [raster] Optional. Wind Speed [raster] Optional. Constant Wind Direction [Degree] [number] Default: 135 Old Version [boolean] Default: True Search Distance [km] [number] Default: 300.0 Acceleration [number] Default: 1.5 Use Pyramids [boolean] Default: True Wind Direction Units [selection] Options: • 0 — [0] radians • 1 — [1] degree Default: 0 Wind Speed Scale Factor [number] Default: 1.0 Outputs Wind Effect [raster] Windward Effect [raster] Leeward Effect [raster] Console usage processing.runalg(’saga:windeffect’, dem, dir, len, dir_const, oldver, maxdist, accel, pyramids, dir_units, len_scale, effect, luv, lee) See also . 18.7. SAGA algorithm provider 591 QGIS User Guide, Release 2.6 18.7.28 Terrain profiles Cross profiles Description Parameters DEM [raster] Lines [vector: line] Profile Distance [number] Default: 10.0 Profile Length [number] Default: 10.0 Profile Samples [number] Default: 10.0 Outputs Cross Profiles [vector] Console usage processing.runalg(’saga:crossprofiles’, dem, lines, dist_line, dist_profile, num_profile, profiles) See also Profile from points table Description Parameters Grid [raster] Input [table] X[tablefield: any] Y[tablefield: any] Outputs Result [table] 592 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’saga:profilefrompointstable’, grid, table, x, y, result) See also Profiles from lines Description Parameters DEM [raster] Values [multipleinput: rasters] Optional. Lines [vector: line] Name [tablefield: any] Each Line as new Profile [boolean] Default: True Outputs Profiles [vector] Profiles [vector] Console usage processing.runalg(’saga:profilesfromlines’, dem, values, lines, name, split, profile, profiles) See also . 18.8 TauDEM algorithm provider TauDEM (Terrain Analysis Using Digital Elevation Models) is a set of Digital Elevation Model (DEM) tools for the extraction and analysis of hydrologic information from topography as represented by a DEM. This is software developed at Utah State University (USU) for hydrologic digital elevation model analysis and watershed delineation. TauDEM is distributed as a set of standalone command line executable programs for a Windows and source code for compiling and use on other systems. Note: Please remember that Processing contains only the interface description, so you need to install TauDEM 5.0.6 by yourself and configure Processing properly. 18.8. TauDEM algorithm provider 593 QGIS User Guide, Release 2.6 Documentation for TauDEM algorithms derived from official TauDEM documentation . 18.8.1 Basic Grid Analysis D8 Contributing Area Description Calculates a grid of contributing areas using the single direction D8 flow model. The contribution of each grid cell is taken as one (or when the optional weight grid is used, the value from the weight grid). The contributing area for each grid cell is taken as its own contribution plus the contribution from upslope neighbors that drain in to it according to the D8 flow model. If the optional outlet point shapefile is used, only the outlet cells and the cells upslope (by the D8 flow model) of them are in the domain to be evaluated. By default, the tool checks for edge contamination. This is defined as the possibility that a contributing area value may be underestimated due to grid cells outside of the domain not being counted. This occurs when drainage is inwards from the boundaries or areas with “no data” values for elevation. The algorithm recognizes this and reports “no data” for the contributing area. It is common to see streaks of “no data” values extending inwards from boundaries along flow paths that enter the domain at a boundary. This is the desired effect and indicates that contributing area for these grid cells is unknown due to it being dependent on terrain outside of the domain of data available. Edge contamination checking may be turned off in cases where you know this is not an issue or want to ignore these problems, if for example, the DEM has been clipped along a watershed outline. Parameters D8 Flow Direction Grid [raster] A grid of D8 flow directions which are defined, for each cell, as the direction of the one of its eight adjacent or diagonal neighbors with the steepest downward slope. This grid can be obtained as the output of the “D8 Flow Directions” tool. Outlets Shapefile [vector: point] Optional. A point shapefile defining the outlets of interest. If this input file is used, only the cells upslope of these outlet cells are considered to be within the domain being evaluated. Weight Grid [raster] Optional. A grid giving contribution to flow for each cell. These contributions (also sometimes referred to as weights or loadings) are used in the contributing area accumulation. If this input file is not used, the contribution to flow will assumed to be one for each grid cell. Check for edge contamination [boolean] A flag that indicates whether the tool should check for edge contamination. Edge contamination is defined as the possibility that a contributing area value may be underestimated due to the fact that grid cells outside of the domain have not been evaluated. This occurs when drainage is inwards from the boundaries or areas with NODATA values for elevation. The algorithm recognizes this and reports NODATA for the impated cells. It is common to see streaks of NODATA values extending inwards from boundaries along flow paths that enter the domain at a boundary. This is the desired effect and indicates that contributing area for these grid cells is unknown due to it being dependent on terrain outside of the domain of available data. Edge contamination checking may be turned off in cases where you know this is not an issue, or want to ignore these problems, if for example, the DEM has been clipped along a watershed outline. Default: True 594 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs D8 Contributing Area Grid [raster] A grid of contributing area values calculated as the cells own con- tribution plus the contribution from upslope neighbors that drain in to it according to the D8 flow model. Console usage processing.runalg(’taudem:d8contributingarea’,-p,-o,-wg,-nc,-ad8) See also D8 Flow Directions Description Creates 2 grids. The first contains the flow direction from each grid cell to one of its adjacent or diagonal neighbors, calculated using the direction of steepest descent. The second contain the slope, as evaluated in the direction of steepest descent, and is reported as drop/distance, i.e. tan of the angle. Flow direction is reported as NODATA for any grid cell adjacent to the edge of the DEM domain, or adjacent to a NODATA value in the DEM. In flat areas, flow directions are assigned away from higher ground and towards lower ground using the method of Garbrecht and Martz (1997). The D8 flow direction algorithm may be applied to a DEM that has not had its pits filled, but it will then result in NODATA values for flow direction and slope at the lowest point of each pit. D8 Flow Direction Coding: • 1 — East • 2 — Northeast • 3 — North • 4 — Northwest • 5 — West • 6 — Southwest • 7 — South • 8 — Southeast The flow direction routing across flat areas is performed according to the method described by Garbrecht, J. and L. W. Martz, (1997), “The Assignment of Drainage Direction Over Flat Surfaces in Raster Digital Elevation Models”, Journal of Hydrology, 193: 204-213. Parameters Pit Filled Elevation Grid [raster] A grid of elevation values. This is usually the output of the “Pit Remove” tool, in which case it is elevations with pits removed. Pits are low elevation areas in digital elevation models (DEMs) that are completely surrounded by higher terrain. They are generally taken to be artifacts of the digitation process that interfere with the processing of flow across DEMs. So they are removed by raising their elevation to the point where they just drain off the domain. This step is not essential if you have reason to believe that the pits in your DEM are real. If a few pits actually exist and so should not be removed, while at the same time others are believed to be artifacts that need to be removed, the actual pits should have NODATA elevation values inserted at their lowest point. NODATA values serve to define edges of the domain in the flow field, and elevations are only raised to where flow is off an edge, so an internal NODATA value will stop a pit from being removed, if necessary. 18.8. TauDEM algorithm provider 595 QGIS User Guide, Release 2.6 Outputs D8 Flow Direction Grid [raster] A grid of D8 flow directions which are defined, for each cell, as the direction of the one of its eight adjacent or diagonal neighbors with the steepest downward slope. D8 Slope Grid [raster] A grid giving slope in the D8 flow direction. This is measured as drop/distance. Console usage processing.runalg(’taudem:d8flowdirections’,-fel,-p,-sd8) See also D-Infinity Contributing Area Description Calculates a grid of specific catchment area which is the contributing area per unit contour length using the multiple flow direction D-infinity approach. D-infinity flow direction is defined as steepest downward slope on planar triangular facets on a block centered grid. The contribution at each grid cell is taken as the grid cell length (or when the optional weight grid input is used, from the weight grid). The contributing area of each grid cell is then taken as its own contribution plus the contribution from upslope neighbors that have some fraction draining to it according to the D-infinity flow model. The flow from each cell either all drains to one neighbor, if the angle falls along a cardinal (0, 휋/2, 휋, 3휋/2) or ordinal (휋/4, 3휋/4, 5휋/4, 7휋/4) direction, or is on an angle falling between the direct angle to two adjacent neighbors. In the latter case the flow is proportioned between these two neighbor cells according to how close the flow direction angle is to the direct angle to those cells. The contour length used here is the grid cell size. The resulting units of the specific catchment area are length units the same as those of the grid cell size. When the optional weight grid is not used, the result is reported in terms of specific catchment area, the upslope area per unit contour length, taken here as the number of cells times grid cell length (cell area divided by cell length). This assumes that grid cell length is the effective contour length, in the definition of specific catchment area and does not distinguish any difference in contour length dependent upon the flow direction. When the optional weight grid is used, the result is reported directly as a summation of weights, without any scaling. If the optional outlet point shapefile is used, only the outlet cells and the cells upslope (by the D-infinity flow model) of them are in the domain to be evaluated. By default, the tool checks for edge contamination. This is defined as the possibility that a contributing area value may be underestimated due to grid cells outside of the domain not being counted. This occurs when drainage is inwards from the boundaries or areas with “no data” values for elevation. The algorithm recognizes this and reports “no data” for the contributing area. It is common to see streaks of “no data” values extending inwards from boundaries along flow paths that enter the domain at a boundary. This is the desired effect and indicates that contributing area for these grid cells is unknown due to it being dependent on terrain outside of the domain of data available. Edge contamination checking may be turned off in cases where you know it is not an issue or want to ignore these problems, if for example, the DEM has been clipped along a watershed outline. Parameters D-Infinity Flow Direction Grid [raster] A grid of flow directions based on the D-infinity flow method using the steepest slope of a triangular facet. Flow direction is determined as the direction of the steepest downward slope on the 8 triangular facets of a 3x3 block centered grid. Flow direction is en- coded as an angle in radians, counter-clockwise from east as a continuous (floating point) quantity between 0 and 2휋. The resulting flow in a grid is then usually interpreted as being proportioned between the two neighboring cells that define the triangular facet with the steepest downward slope. 596 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outlets Shapefile [vector: point] Optional. A point shapefile defining the outlets of interest. If this input file is used, only the cells upslope of these outlet cells are considered to be within the domain being evaluated. Weight Grid [raster] Optional. A grid giving contribution to flow for each cell. These contributions (also sometimes referred to as weights or loadings) are used in the contributing area accumulation. If this input file is not used, the result is reported in terms of specific catchment area (the upslope area per unit contour length) taken as the number of cells times grid cell length (cell area divided by cell length). Check for edge contamination [boolean] A flag that indicates whether the tool should check for edge contamination. Edge contamination is defined as the possibility that a contributing area value may be underestimated due to the fact that grid cells outside of the domain have not been evaluated. This occurs when drainage is inwards from the boundaries or areas with NODATA values for elevation. The algorithm recognizes this and reports NODATA for the impated cells. It is common to see streaks of NODATA values extending inwards from boundaries along flow paths that enter the domain at a boundary. This is the desired effect and indicates that contributing area for these grid cells is unknown due to it being dependent on terrain outside of the domain of available data. Edge contamination checking may be turned off in cases where you know this is not an issue, or want to ignore these problems, if for example, the DEM has been clipped along a watershed outline. Default: True Outputs D-Infinity Specific Catchment Area Grid [raster] A grid of specific catchment area which is the contributing area per unit contour length using the multiple flow direction D-infinity approach. The con- tributing area of each grid cell is then taken as its own contribution plus the contribution from upslope neighbors that have some fraction draining to it according to the D-infinity flow model. Console usage processing.runalg(’taudem:dinfinitycontributingarea’,-ang,-o,-wg,-nc,-sca) See also D-Infinity Flow Directions Description Assigns a flow direction based on the D-infinity flow method using the steepest slope of a triangular facet (Tar- boton, 1997, “A New Method for the Determination of Flow Directions and Contributing Areas in Grid Digital Elevation Models”, Water Resources Research, 33(2): 309-319). Flow direction is defined as steepest down- ward slope on planar triangular facets on a block centered grid. Flow direction is encoded as an angle in radians counter-clockwise from east as a continuous (floating point) quantity between 0 and 2휋. The flow direction angle is determined as the direction of the steepest downward slope on the eight triangular facets formed in a 3 x 3 grid cell window centered on the grid cell of interest. The resulting flow in a grid is then usually interpreted as being proportioned between the two neighboring cells that define the triangular facet with the steepest downward slope. A block-centered representation is used with each elevation value taken to represent the elevation of the center of the corresponding grid cell. Eight planar triangular facets are formed between each grid cell and its eight neighbors. Each of these has a downslope vector which when drawn outwards from the center may be at an angle that lies within or outside the 45 degree (휋/4 radian) angle range of the facet at the center point. If the slope vector 18.8. TauDEM algorithm provider 597 QGIS User Guide, Release 2.6 angle is within the facet angle, it represents the steepest flow direction on that facet. If the slope vector angle is outside a facet, the steepest flow direction associated with that facet is taken along the steepest edge. The slope and flow direction associated with the grid cell is taken as the magnitude and direction of the steepest downslope vector from all eight facets. Slope is measured as drop/distance, i.e. tan of the slope angle. In the case where no slope vectors are positive (downslope), the flow direction is set using the method of Garbrecht and Martz (1997) for the determination of flow across flat areas. This makes flat areas drain away from high ground and towards low ground. The flow path grid to enforce drainage along existing streams is an optional input, and if used, takes precedence over elevations for the setting of flow directions. The D-infinity flow direction algorithm may be applied to a DEM that has not had its pits filled, but it will then result in “no data” values for the D-infinity flow direction and slope associated with the lowest point of the pit. Parameters Pit Filled Elevation Grid [raster] A grid of elevation values. This is usually the output of the “Pit Remove” tool, in which case it is elevations with pits removed. Outputs D-Infinity Flow Directions Grid [raster] A grid of flow directions based on the D-infinity flow method using the steepest slope of a triangular facet. Flow direction is determined as the direction of the steepest downward slope on the 8 triangular facets of a 3x3 block centered grid. Flow direction is en- coded as an angle in radians, counter-clockwise from east as a continuous (floating point) quantity between 0 and 2휋. The resulting flow in a grid is then usually interpreted as being proportioned between the two neighboring cells that define the triangular facet with the steepest downward slope. D-Infinity Slope Grid [raster] A grid of slope evaluated using the D-infinity method described in Tar- boton, D. G., (1997), “A New Method for the Determination of Flow Directions and Contributing Areas in Grid Digital Elevation Models”, Water Resources Research, 33(2): 309-319. This is the steepest outwards slope on one of eight triangular facets centered at each grid cell, measured as drop/distance, i.e. tan of the slope angle. Console usage processing.runalg(’taudem:dinfinityflowdirections’,-fel,-ang,-slp) See also Grid Network Description Creates 3 grids that contain for each grid cell: 1) the longest path, 2) the total path, and 3) the Strahler order number. These values are derived from the network defined by the D8 flow model. The longest upslope length is the length of the flow path from the furthest cell that drains to each cell. The total upslope path length is the length of the entire grid network upslope of each grid cell. Lengths are measured between cell centers taking into account cell size and whether the direction is adjacent or diagonal. Strahler order is defined as follows: A network of flow paths is defined by the D8 Flow Direction grid. Source flow paths have a Strahler order number of one. When two flow paths of different order join the order of the downstream flow path is the order of the highest incoming flow path. When two flow paths of equal order join the downstream flow path order is increased by 1. When more than two flow paths join the downstream flow path order is calculated as the maximum of the highest incoming flow path order or the second highest incoming flow path order + 1. This generalizes the common definition to cases where more than two flow paths join at a point. 598 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Where the optional mask grid and threshold value are input, the function is evaluated only considering grid cells that lie in the domain with mask grid value greater than or equal to the threshold value. Source (first order) grid cells are taken as those that do not have any other grid cells from inside the domain draining in to them, and only when two of these flow paths join is order propagated according to the ordering rules. Lengths are also only evaluated counting paths within the domain greater than or equal to the threshold. If the optional outlet point shapefile is used, only the outlet cells and the cells upslope (by the D8 flow model) of them are in the domain to be evaluated. Parameters D8 Flow Direction Grid [raster] A grid of D8 flow directions which are defined, for each cell, as the direction of the one of its eight adjacent or diagonal neighbors with the steepest downward slope. This grid can be obtained as the output of the “D8 Flow Directions” tool. Outlets Shapefile [vector: point] Optional. A point shapefile defining the outlets of interest. If this input file is used, only the cells upslope of these outlet cells are considered to be within the domain being evaluated. Mask Grid [raster] Optional. A grid that is used to determine the domain do be analyzed. If the mask grid value >= mask threshold (see below), then the cell will be included in the domain. While this tool does not have an edge contamination flag, if edge contamination analysis is needed, then a mask grid from a function like “D8 Contributing Area” that does support edge contamination can be used to achieve the same result. Mask Threshold [number] This input parameter is used in the calculation mask grid value >= mask threshold to determine if the grid cell is in the domain to be analyzed. Default: 100 Outputs Longest Upslope Length Grid [raster] A grid that gives the length of the longest upslope D8 flow path terminating at each grid cell. Lengths are measured between cell centers taking into account cell size and whether the direction is adjacent or diagonal. Total Upslope Length Grid [raster] The total upslope path length is the length of the entire D8 flow grid network upslope of each grid cell. Lengths are measured between cell centers taking into account cell size and whether the direction is adjacent or diagonal. Strahler Network Order Grid [raster] A grid giving the Strahler order number for each cell. A net- work of flow paths is defined by the D8 Flow Direction grid. Source flow paths have a Strahler order number of one. When two flow paths of different order join the order of the downstream flow path is the order of the highest incoming flow path. When two flow paths of equal order join the downstream flow path order is increased by 1. When more than two flow paths join the downstream flow path order is calculated as the maximum of the highest incoming flow path order or the second highest incoming flow path order + 1. This generalizes the common definition to cases where more than two flow paths join at a point. Console usage processing.runalg(’taudem:gridnetwork’, d8_flow_dir_grid, outlets_shape, mask_grid, threshold, longest_len_grid, total_len_grid, strahler_grid) 18.8. TauDEM algorithm provider 599 QGIS User Guide, Release 2.6 See also Pit Remove Description Identifies all pits in the DEM and raises their elevation to the level of the lowest pour point around their edge. Pits are low elevation areas in digital elevation models (DEMs) that are completely surrounded by higher terrain. They are generally taken to be artifacts that interfere with the routing of flow across DEMs, so are removed by raising their elevation to the point where they drain off the edge of the domain. The pour point is the lowest point on the boundary of the “watershed” draining to the pit. This step is not essential if you have reason to believe that the pits in your DEM are real. If a few pits actually exist and so should not be removed, while at the same time others are believed to be artifacts that need to be removed, the actual pits should have NODATA elevation values inserted at their lowest point. NODATA values serve to define edges in the domain, and elevations are only raised to where flow is off an edge, so an internal NODATA value will stop a pit from being removed, if necessary. Parameters Elevation Grid [raster] A digital elevation model (DEM) grid to serve as the base input for the terrain analysis and stream delineation. Outputs Pit Removed Elevation Grid [raster] A grid of elevation values with pits removed so that flow is routed off of the domain. Console usage processing.runalg(’taudem:pitremove’,-z,-fel) See also . 18.8.2 Specialized Grid Analysis D8 Distance To Streams Description Computes the horizontal distance to stream for each grid cell, moving downslope according to the D8 flow model, until a stream grid cell is encountered. Parameters D8 Flow Direction Grid [raster] This input is a grid of flow directions that are encoded using the D8 method where all flow from a cells goes to a single neighboring cell in the direction of steepest descent. This grid can be obtained as the output of the “D8 Flow Directions” tool. 600 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Stream Raster Grid [raster] A grid indicating streams. Such a grid can be created by several of the tools in the “Stream Network Analysis” toolset. However, the tools in the “Stream Network Analysis” toolset only create grids with a value of 0 for no stream, or 1 for stream cells. This tool can also accept grids with values greater than 1, which can be used in conjunction with the Threshold parameter to determine the location of streams. This allows Contributing Area grids to be used to define streams as well as the normal Stream Raster grids. This grid expects integer (long integer) values and any non-integer values will be truncated to an integer before being evaluated. Threshold [number] This value acts as threshold on the Stream Raster Grid to determine the location of streams. Cells with a Stream Raster Grid value greater than or equal to the Threshold value are interpreted as streams. Default: 50 Outputs Output Distance to Streams [raster] A grid giving the horizontal distance along the flow path as de- fined by the D8 Flow Directions Grid to the streams in the Stream Raster Grid. Console usage processing.runalg(’taudem:d8distancetostreams’,-p,-src,-thresh,-dist) See also D-Infinity Avalanche Runout Description Identifies an avalanche’s affected area and the flow path length to each cell in that affacted area. All cells downs- lope from each source area cell, up to the point where the slope from the source to the affected area is less than a threshold angle called the Alpha Angle can be in the affected area. This tool uses the D-infinity multiple flow direction method for determining flow direction. This will likely cause very small amounts of flow to be dispersed to some downslope cells that might overstate the affected area, so a threshold proportion can be set to avoid this excess dispersion. The flow path length is the distance from the cell in question to the source cell that has the highest angle. All points downslope from the source area are potentially in the affected area, but not beyond a point where the slope from the source to the affected area is less than a threshold angle called the Alpha Angle. Slope is to be measured using the straight line distance from source point to evaluation point. It makes more physical sense to me for the angle to be measured along the flow path. Nevertheless it is equally easy to code straight line angles as angles along the flow path, so an option that allows switching will be provided. The most practical way to evaluate avalanche runout is to keep track of the source point with the greatest angle to each point. Then the recursive upslope flow algebra approach will look at a grid cell and all its upslope neighbors that flow to it. Information from the upslope neighbors will be used to calculate the angle to the grid cell in question and retain it in the runout zone if the angle exceeds the alpha angle. This procedure makes the assumption that the maximum angle at a grid cell will be from the set of cells that have maximum angles to the inflowing neighbors. This will always be true of angle is calculated along a flow path, but I can conceive of cases where flow paths bend back on themselves where this would not be the case for straight line angles. The D-infinity multiple flow direction field assigns flow from each grid cell to multiple downslope neighbors using proportions (Pik) that vary between 0 and 1 and sum to 1 for all flows out of a grid cell. It may be desirable to specify a threshold T that this proportion has to exceed before a grid cell is counted as flowing to a downslope 18.8. TauDEM algorithm provider 601 QGIS User Guide, Release 2.6 grid cell, e.g. Pik > T (=0.2 say) to avoid dispersion to grid cells that get very little flow. T will be specified as a user input. If all upslope grid cells are to be used T may be input as 0. Avalanche source sites are to be input as a short integer grid (name suffix *ass, e.g. demass) comprised of positive values where avalanches may be triggered and 0 values elsewhere. The following grids are output: • rz — A runout zone indicator with value 0 to indicate that this grid cell is not in the runout zone and value > 0 to indicate that this grid cell is in the runout zone. Since there may be information in the angle to the associated source site, this variable will be assigned the angle to the source site (in degrees) • dm — Along flow distance from the source site that has the highest angle to the point in question Parameters D-Infinity Flow Direction Grid [raster] A grid giving flow direction by the D-infinity method. Flow direction is measured in radians, counter clockwise from east. This can be created by the tool “D- Infinity Flow Directions”. Pit Filled Elevation Grid [raster] This input is a grid of elevation values. As a general rule, it is recommended that you use a grid of elevation values that have had the pits removed for this input. Pits are generally taken to be artifacts that interfere with the analysis of flow across them. This grid can be obtained as the output of the “Pit Remove” tool, in which case it contains elevation values where the pits have been filled to the point where they just drain. Avalanche Source Site Grid [raster] This is a grid of source areas for snow avalanches that are com- monly identified manually using a mix of experience and visual interpretation of maps. Avalanche source sites are to be input as a short integer grid (name suffix *ass, e.g. demass) comprised of positive values where avalanches may be triggered and 0 values elsewhere. Proportion Threshold [number] This value is a threshold proportion that is used to limit the disperson of flow caused by using the D-infinity multiple flow direction method for determining flow direction. The D-infinity multiple flow direction method often causes very small amounts of flow to be dispersed to some downslope cells that might overstate the affected area, so a threshold proportion can be set to avoid this excess dispersion. Default: 0.2 Alpha Angle Threshold [number] This value is the threshold angle, called the Alpha Angle, that is used to determine which of the cells downslope from the source cells are in the affected area. Only the cells downslope from each source area cell, up to the point where the slope from the source to the affected area is less than a threshold angle are in the affected area. Default: 18 Measure distance along flow path [boolean] This option selects the method used to measure the distance used to calculate the slope angle. If option is True then measure it along the flow path, where the False option causes the slope to be measure along the straight line distance from the source cell to the evaluation cell. Default: True Outputs Runout Zone Grid [raster] This grid Identifies the avalanche’s runout zone (affected area) using a runout zone indicator with value 0 to indicate that this grid cell is not in the runout zone and value > 0 to indicate that this grid cell is in the runout zone. Since there may be information in the angle to the associated source site, this variable will be assigned the angle to the source site (in degrees). Path Distance Grid [raster] This is a grid of the flow distance from the source site that has the highest angle to each cell. 602 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’taudem:dinfinityavalancherunout’,-ang,-fel,-ass,-thresh,-alpha,-direct,-rz,-dfs) See also D-Infinity Concentration Limited Accumulation Description This function applies to the situation where an unlimited supply of a substance is loaded into flow at a concentra- tion or solubility threshold Csol over a region indicated by an indicator grid (dg). It a grid of the concentration of a substance at each location in the domain, where the supply of substance from a supply area is loaded into the flow at a concentration or solubility threshold. The flow is first calculated as a D-infinity weighted contributing area of an input Effective Runoff Weight Grid (notionally excess precipitation). The concentation of substance over the supply area (indicator grid) is at the concentration threshold. As the substance moves downslope with the D-infinity flow field, it is subject to first order decay in moving from cell to cell as well as dilution due to changes in flow. The decay multiplier grid gives the fractional (first order) reduction in quantity in moving from grid cell x to the next downslope cell. If the outlets shapefile is used, the tool only evaluates the part of the domain that contributes flow to the locations given by the shapefile. This is useful for a tracking a contaminant or compound from an area with unlimited supply of that compound that is loaded into a flow at a concentration or solubility threshold over a zone and flow from the zone may be subject to decay or attenuation. The indicator grid (dg) is used to delineate the area of the substance supply using the (0, 1) indicator function i(x). A[] denotes the weighted accumulation operator evaluated using the D-Infinity Contributing Area func- tion. The Effective Runoff Weight Grid gives the supply to the flow (e.g. the excess rainfall if this is overland flow) denoted as w(x). The specific discharge is then given by: Q(x)=A[w(x)] This weighted accumulation Q(x) is output as the Overland Flow Specific Discharge Grid. Over the substance supply area concentration is at the threshold (the threshold is a saturation or solubility limit). If i(x) = 1, then C(x) = Csol, and L(x) = Csol Q(x), where L(x) denotes the load being carried by the flow. At remaining locations, the load is determined by load accumulation and the concentration by dilution: Here d(x) = d(i, j) is a decay multiplier giving the fractional (first order) reduction in mass in moving from grid cell x to the next downslope cell. If travel (or residence) times t(x) associated with flow between cells are available d(x) may be evaluated as exp(-k t(x)) where k is a first order decay parameter. The Concentration grid output is C(x). If the outlets shapefile is used, the tool only evaluates the part of the domain that contributes flow to the locations given by the shapefile. Useful for a tracking a contaminant released or partitioned to flow at a fixed threshold concentration. Parameters D-Infinity Flow Direction Grid [raster] A grid giving flow direction by the D-infinity method. Flow direction is measured in radians, counter clockwise from east. This grid can be created by the function “D-Infinity Flow Directions”. Disturbance Indicator Grid [raster] A grid that indicates the source zone of the area of substance supply and must be 1 inside the zone and 0 or NODATA over the rest of the domain. 18.8. TauDEM algorithm provider 603 QGIS User Guide, Release 2.6 Decay Multiplier Grid [raster] A grid giving the factor by which flow leaving each grid cell is multiplied before accumulation on downslope grid cells. This may be used to simulate the movement of an attenuating or decaying substance. If travel (or residence) times t(x) associated with flow between cells are available d(x) may be evaluated as exp(-k t(x)) where k is a first order decay parameter. Effective Runoff Weight Grid [raster] A grid giving the input quantity (notionally effective runoff or excess precipitation) to be used in the D-infinity weighted contributing area evaluation of Overland Flow Specific Discharge. Outlets shapefile [vector: point] Optional. This optional input is a point shapefile defining outlets of interest. If this file is used, the tool will only evaluate the area upslope of these outlets. Concentration Threshold [number] The concentration or solubility threshold. Over the substance sup- ply area, concentration is at this threshold. Default: 1.0 Check for edge contamination [boolean] This option determines whether the tool should check for edge contamination. Edge contamination is defined as the possibility that a value may be underestimated due to grid cells outside of the domain not being considered when determining contributing area. Default: True Outputs Concentration Grid [raster] A grid giving the resulting concentration of the compound of interest in the flow. Console usage processing.runalg(’taudem:dinfinityconcentrationlimitedaccumulation’,-ang,-dg,-dm,-q,-o,-csol,-nc,-ctpt) See also D-Infinity Decaying Accumulation Description The D-Infinity Decaying Accumulation tool creates a grid of the accumulated quantity at each location in the domain where the quantity accumulates with the D-infinity flow field, but is subject to first order decay in moving from cell to cell. By default, the quantity contribution of each grid cell is the cell length to give a per unit width accumulation, but can optionally be expressed with a weight grid. The decay multiplier grid gives the fractional (first order) reduction in quantity in accumulating from grid cell x to the next downslope cell. A decayed accumulation operator DA[.] takes as input a mass loading field m(x) expressed at each grid location as m(i, j) that is assumed to move with the flow field but is subject to first order decay in moving from cell to cell. The output is the accumulated mass at each location DA(x). The accumulation of m at each grid cell can be numerically evaluated. Here d(x) = d(i ,j) is a decay multiplier giving the fractional (first order) reduction in mass in moving from grid cell x to the next downslope cell. If travel (or residence) times t(x) associated with flow between cells are available d(x) may be evaluated as exp(-k t(x)) where k is a first order decay parameter. The weight grid is used to represent the mass loading m(x). If not specified this is taken as 1. If the outlets shapefile is used the function is only evaluated on that part of the domain that contributes flow to the locations given by the shapefile. 604 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Useful for a tracking contaminant or compound subject to decay or attenuation. Parameters D-Infinity Flow Direction Grid [raster] A grid giving flow direction by the D-infinity method. Flow direction is measured in radians, counter clockwise from east. This grid can be created by the function “D-Infinity Flow Directions”. Decay Multiplier Grid [raster] A grid giving the factor by which flow leaving each grid cell is multiplied before accumulation on downslope grid cells. This may be used to simulate the movement of an attenuating substance. Weight Grid [raster] Optional. A grid giving weights (loadings) to be used in the accumulation. If this optional grid is not specified, weights are taken as the linear grid cell size to give a per unit width accumulation. Outlets Shapefile [vector: point] Optional. This optional input is a point shapefile defining outlets of interest. If this file is used, the tool will only evaluate ther area upslope of these outlets. Check for edge contamination [boolean] This option determines whether the tool should check for edge contamination. Edge contamination is defined as the possibility that a value may be underestimated due to grid cells outside of the domain not being considered when determining contributing area. Default: True Outputs Decayed Specific Catchment Area Grid [raster] The D-Infinity Decaying Accumulation tool cre- ates a grid of the accumulated mass at each location in the domain where mass moves with the D-infinity flow field, but is subject to first order decay in moving from cell to cell. Console usage processing.runalg(’taudem:dinfinitydecayingaccumulation’,-ang,-dm,-wg,-o,-nc,-dsca) See also D-Infinity Distance Down Description Calculates the distance downslope to a stream using the D-infinity flow model. The D-infinity flow model is a multiple flow direction model, because the outflow from each grid cell is proportioned between up to 2 downslope grid cells. As such, the distance from any grid cell to a stream is not uniquely defined. Flow that originates at a particular grid cell may enter the stream at a number of different cells. The statistical method may be selected as the longest, shortest or weighted average of the flow path distance to the stream. Also one of several ways of measuring distance may be selected: the total straight line path (Pythagoras), the horizontal component of the straight line path, the vertical component of the straight line path, or the total surface flow path. Parameters D-Infinity Flow Direction Grid [raster] A grid giving flow direction by the D-infinity method. Flow direction is measured in radians, counter clockwise from east. This can be created by the tool “D- Infinity Flow Directions”. 18.8. TauDEM algorithm provider 605 QGIS User Guide, Release 2.6 Pit Filled Elevation Grid [raster] This input is a grid of elevation values. As a general rule, it is recommended that you use a grid of elevation values that have had the pits removed for this input. Pits are generally taken to be artifacts that interfere with the analysis of flow across them. This grid can be obtained as the output of the “Pit Remove” tool, in which case it contains elevation values where the pits have been filled to the point where they just drain. Stream Raster Grid [raster] A grid indicating streams, by using a grid cell value of 1 on streams and 0 off streams. This is usually the output of one of the tools in the “Stream Network Analysis” toolset. Weight Path Grid [raster] Optional. A grid giving weights (loadings) to be used in the distance calculation. This might be used for example where only flow distance through a buffer is to be calculated. The weight is then 1 in the buffer and 0 outside it. Alternatively the weight may reflect some sort of cost function for travel over the surface, perhaps representing travel time or attenuation of a process. If this input file is not used, the loadings will assumed to be one for each grid cell. Statistical Method [selection] Statistical method used to calculate the distance down to the stream. In the D-Infinity flow model, the outflow from each grid cell is proportioned between two downslope grid cells. Therefore, the distance from any grid cell to a stream is not uniquely defined. Flow that originates at a particular grid cell may enter the stream at a number of cells. The distance to the stream may be defined as the longest (maximum), shortest (minimum) or weighted average of the distance down to the stream. Options: • 0 — Minimum • 1 — Maximum • 2 — Average Default: 2 Distance Method [selection] Distance method used to calculate the distance down to the stream. One of several ways of measuring distance may be selected: the total straight line path (Pythagoras), the horizontal component of the straight line path (horizontal), the vertical component of the straight line path (vertical), or the total surface flow path (surface). Options: • 0 — Pythagoras • 1 — Horizontal • 2 — Vertical • 3 — Surface Default: 1 Check for edge contamination [boolean] A flag that determines whether the tool should check for edge contamination. This is defined as the possibility that a value may be underestimated due to grid cells outside of the domain not being counted. In the context of Distance Down this occurs when part of a flow path traced downslope from a grid cell leaves the domain without reaching a stream grid cell. With edge contamination checking selected, the algorithm recognizes this and reports no data for the result. This is the desired effect and indicates that values for these grid cells is unknown due to it being dependent on terrain outside of the domain of data available. Edge contamination checking may be overridden in cases where you know this is not an issue or want to evaluate the distance using only the fraction of flow paths that terminate at a stream. Default: True Outputs D-Infinity Drop to Stream Grid [raster] Grid containing the distance to stream calculated using the D-infinity flow model and the statistical and path methods chosen. 606 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’taudem:dinfinitydistancedown’, dinf_flow_dir_grid, pit_filled_grid, stream_grid, weight_path_grid, stat_method, dist_method, edge_contam, dist_down_grid) See also D-Infinity Distance Up Description This tool calculates the distance from each grid cell up to the ridge cells along the reverse D-infinity flow directions. Ridge cells are defined to be grid cells that have no contribution from grid cells further upslope. Given the convergence of multiple flow paths at any grid cell, any given grid cell can have multiple upslope ridge cells. There are three statictical methods that this tool can use: maximum distance, minimum distance and waited flow average over these flow paths. A variant on the above is to consider only grid cells that contribute flow with a proportion greater than a user specified threshold (t) to be considered as upslope of any given grid cell. Setting t=0.5 would result in only one flow path from any grid cell and would give the result equivalent to a D8 flow model, rather than D-infinity flow model, where flow is proportioned between two downslope grid cells. Finally there are several different optional paths that can be measured: the total straight line path (Pythagoras), the horizontal component of the straight line path, the vertical component of the straight line path, or the total surface flow path. Parameters D-Infinity Flow Direction Grid [raster] A grid giving flow direction by the D-infinity method. Flow direction is measured in radians, counter clockwise from east. This can be created by the tool “D- Infinity Flow Directions”. Pit Filled Elevation Grid [raster] This input is a grid of elevation values. As a general rule, it is recommended that you use a grid of elevation values that have had the pits removed for this input. Pits are generally taken to be artifacts that interfere with the analysis of flow across them. This grid can be obtained as the output of the “Pit Remove” tool, in which case it contains elevation values where the pits have been filled to the point where they just drain. Slope Grid [raster] This input is a grid of slope values. This is measured as drop/distance and it is most often obtained as the output of the “D-Infinity Flow Directions” tool. Statistical Method [selection] Statistical method used to calculate the distance down to the stream. In the D-Infinity flow model, the outflow from each grid cell is proportioned between two downslope grid cells. Therefore, the distance from any grid cell to a stream is not uniquely defined. Flow that originates at a particular grid cell may enter the stream at a number of cells. The distance to the stream may be defined as the longest (maximum), shortest (minimum) or weighted average of the distance down to the stream. Options: • 0 — Minimum • 1 — Maximum • 2 — Average Default: 2 Distance Method [selection] Distance method used to calculate the distance down to the stream. One of several ways of measuring distance may be selected: the total straight line path (Pythagoras), the horizontal component of the straight line path (horizontal), the vertical component of the straight line path (vertical), or the total surface flow path (surface). Options: • 0 — Pythagoras 18.8. TauDEM algorithm provider 607 QGIS User Guide, Release 2.6 • 1 — Horizontal • 2 — Vertical • 3 — Surface Default: 1 Proportion Threshold [number] The proportion threshold parameter where only grid cells that contribute flow with a proportion greater than this user specified threshold (t) is considered to be upslope of any given grid cell. Setting t=0.5 would result in only one flow path from any grid cell and would give the result equivalent to a D8 flow model, rather than D-Infinity flow model, where flow is proportioned between two downslope grid cells. Default: 0.5 Check for edge contamination [boolean] A flag that determines whether the tool should check for edge contamination. This is defined as the possibility that a value may be underestimated due to grid cells outside of the domain not being counted. Default: True Outputs D-Infinity Distance Up [raster] Grid containing the distances up to the ridge calculated using the D- Infinity flow model and the statistical and path methods chosen. Console usage processing.runalg(’taudem:dinfinitydistanceup’, dinf_flow_dir_grid, pit_filled_grid, slope_grid, stat_method, dist_method, threshold, edge_contam, dist_up_grid) See also D-Infinity Reverse Accumulation Description This works in a similar way to evaluation of weighted Contributing area, except that the accumulation is by propagating the weight loadings upslope along the reverse of the flow directions to accumulate the quantity of weight loading downslope from each grid cell. The function also reports the maximum value of the weight loading downslope from each grid cell in the Maximum Downslope grid. This function is designed to evaluate and map the hazard due to activities that may have an effect downslope. The example is land management activities that increase runoff. Runoff is sometimes a trigger for landslides or debris flows, so the weight grid here could be taken as a terrain stability map. Then the reverse accumulation provides a measure of the amount of unstable terrain downslope from each grid cell, as an indicator of the danger of activities that may increase runoff, even though there may be no potential for any local impact. Parameters D-Infinity Flow Direction Grid [raster] A grid giving flow direction by the D-infinity method. Flow direction is measured in radians, counter clockwise from east. This can be created by the tool “D- Infinity Flow Directions”. Weight Grid [raster] A grid giving weights (loadings) to be used in the accumulation. 608 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Reverse Accumulation Grid [raster] The grid giving the result of the “Reverse Accumulation” func- tion. This works in a similar way to evaluation of weighted Contributing area, except that the accumulation is by propagating the weight loadings upslope along the reverse of the flow directions to accumulate the quantity of loading downslope from each grid cell. Maximum Downslope Grid [raster] The grid giving the maximum of the weight loading grid downslope from each grid cell. Console usage processing.runalg(’taudem:dinfinityreverseaccumulation’,-ang,-wg,-racc,-dmax) See also D-Infinity Transport Limited Accumulation - 2 Description This function is designed to calculate the transport and deposition of a substance (e.g. sediment) that may be limited by both supply and the capacity of the flow field to transport it. This function accumulates substance flux (e.g. sediment transport) subject to the rule that transport out of any grid cell is the minimum between supply and transport capacity, Tcap. The total supply at a grid cell is calculated as the sum of the transport in from upslope grid cells, Tin, plus the local supply contribution, E(e.g. erosion). This function also outputs deposition, D, calculated as total supply minus actual transport. Here E is the supply. Tout at each grid cell becomes Tin for downslope grid cells and is reported as Transport limited accumulation (tla). D is deposition (tdep). The function provides the option to evaluate concentration of a compound (contaminant) adhered to the transported substance. This is evaluated as follows: Where Lin is the total incoming compound loading and Cin and Tin refer to the Concentration and Transport entering from each upslope grid cell. If else where Cs is the concentration supplied locally and the difference in the second term on the right represents the additional supply from the local grid cell. Then, Cout at each grid cell comprises is the concentration grid output from this function. If the outlets shapefile is used the tool only evaluates that part of the domain that contributes flow to the locations given by the shapefile. Transport limited accumulation is useful for modeling erosion and sediment delivery, including the spatial depen- dence of sediment delivery ratio and contaminant that adheres to sediment. 18.8. TauDEM algorithm provider 609 QGIS User Guide, Release 2.6 Parameters D-Infinity Flow Direction Grid [raster] A grid giving flow direction by the D-infinity method. Flow direction is measured in radians, counter clockwise from east. This can be created by the tool “D- Infinity Flow Directions”. Supply Grid [raster] A grid giving the supply (loading) of material to a transport limited accumulation func- tion. In the application to erosion, this grid would give the erosion detachment, or sediment supplied at each grid cell. Transport Capacity Grid [raster] A grid giving the transport capacity at each grid cell for the transport limited accumulation function. In the application to erosion this grid would give the transport capacity of the carrying flow. Input Concentration Grid [raster] A grid giving the concentration of a compound of interest in the supply to the transport limited accumulation function. In the application to erosion, this grid would give the concentration of say phosphorous adhered to the eroded sediment. Outlets Shapefile [vector: point] Optional. This optional input is a point shapefile defining outlets of interest. If this file is used, the tool will only evaluate the area upslope of these outlets. Check for edge contamination [boolean] This option determines whether the tool should check for edge contamination. Edge contamination is defined as the possibility that a value may be underestimated due to grid cells outside of the domain not being considered when determining the result. Default: True Outputs Transport Limited Accumulation Grid [raster] This grid is the weighted accumulation of supply accumulated respecting the limitations in transport capacity and reports the transport rate calculated by accumulating the substance flux subject to the rule that the transport out of any grid cell is the minimum of the total supply (local supply plus transport in) to that grid cell and the transport capacity. Deposition Grid [raster] A grid giving the deposition resulting from the transport limited accumulation. This is the residual from the transport in to each grid cell minus the transport capacity out of the grid cell. The deposition grid is calculated as the transport in + the local supply - the tranport out. Output Concentration Grid [raster] If an input concentation in supply grid is given, then this grid is also output and gives the concentration of a compound (contaminant) adhered or bound to the transported substance (e.g. sediment) is calculated. Console usage processing.runalg(’taudem:dinfinitytransportlimitedaccumulation2’, dinf_flow_dir_grid, supply_grid, capacity_grid, in_concentr_grid, outlets_shape, edge_contam, transp_lim_accum_grid, deposition_grid, out_concentr_grid) 610 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 See also D-Infinity Transport Limited Accumulation Description This function is designed to calculate the transport and deposition of a substance (e.g. sediment) that may be limited by both supply and the capacity of the flow field to transport it. This function accumulates substance flux (e.g. sediment transport) subject to the rule that transport out of any grid cell is the minimum between supply and transport capacity, Tcap. The total supply at a grid cell is calculated as the sum of the transport in from upslope grid cells, Tin, plus the local supply contribution, E(e.g. erosion). This function also outputs deposition, D, calculated as total supply minus actual transport. Here E is the supply. Tout at each grid cell becomes Tin for downslope grid cells and is reported as Transport limited accumulation (tla). D is deposition (tdep). The function provides the option to evaluate concentration of a compound (contaminant) adhered to the transported substance. This is evaluated as follows: Where Lin is the total incoming compound loading and Cin and Tin refer to the Concentration and Transport entering from each upslope grid cell. If else where Cs is the concentration supplied locally and the difference in the second term on the right represents the additional supply from the local grid cell. Then, Cout at each grid cell comprises is the concentration grid output from this function. If the outlets shapefile is used the tool only evaluates that part of the domain that contributes flow to the locations given by the shapefile. Transport limited accumulation is useful for modeling erosion and sediment delivery, including the spatial depen- dence of sediment delivery ratio and contaminant that adheres to sediment. Parameters D-Infinity Flow Direction Grid [raster] A grid giving flow direction by the D-infinity method. Flow direction is measured in radians, counter clockwise from east. This can be created by the tool “D- Infinity Flow Directions”. Supply Grid [raster] A grid giving the supply (loading) of material to a transport limited accumulation func- tion. In the application to erosion, this grid would give the erosion detachment, or sediment supplied at each grid cell. Transport Capacity Grid [raster] A grid giving the transport capacity at each grid cell for the transport limited accumulation function. In the application to erosion this grid woul give the transport capacity of the carrying flow. Outlets Shapefile [vector: point] Optional. This optional input is a point shapefile defining outlets of interest. If this file is used, the tool will only evaluate the area upslope of these outlets. Check for edge contamination [boolean] This option determines whether the tool should check for edge contamination. Edge contamination is defined as the possibility that a value may be underestimated due to grid cells outside of the domain not being considered when determining the result. 18.8. TauDEM algorithm provider 611 QGIS User Guide, Release 2.6 Default: True Outputs Transport Limited Accumulation Grid [raster] This grid is the weighted accumulation of supply accumulated respecting the limitations in transport capacity and reports the transport rate calculated by accumulating the substance flux subject to the rule that the transport out of any grid cell is the minimum of the total supply (local supply plus transport in) to that grid cell and the transport capacity. Deposition Grid [raster] A grid giving the deposition resulting from the transport limited accumulation. This is the residual from the transport in to each grid cell minus the transport capacity out of the grid cell. The deposition grid is calculated as the transport in + the local supply - the tranport out. Console usage processing.runalg(’taudem:dinfinitytransportlimitedaccumulation’, dinf_flow_dir_grid, supply_grid, capacity_grid, outlets_shape, edge_contam, transp_lim_accum_grid, deposition_grid) See also D-Infinity Upslope Dependence Description The D-Infinity Upslope Dependence tool quantifies the amount each grid cell in the domain contributes to a destination set of grid cells. D-Infinity flow directions proportion flow from each grid cell between multiple downslope grid cells. Following this flow field downslope the amount of flow originating at each grid cell that reaches the destination zone is defined. Upslope influence is evaluated using a downslope recursion, examining grid cells downslope from each grid cell, so that the map produced identifies the area upslope where flow through the destination zone originates, or the area it depends on, for its flow. The figures below illustrate the amount each source point in the domain x (blue) contributes to the destination point or zone y (red). If the indicator weighted contributing area function is denoted I(y; x) giving the weighted contribution using a unit value (1) from specific grid cells y to grid cells x, then the upslope dependence is: D(x; y) = I(y; x). This is useful for example to track where flow or a flow related substance or contaminant that enters a destination area may come from. Parameters D-Infinity Flow Direction Grid [raster] A grid giving flow direction by the D-Infinity method where the flow direction angle is determined as the direction of the steepest downward slope on the eight triangular facets formed in a 3x3 grid cell window centered on the grid cell of interest. This grid can be produced using the “D-Infinity Flow Direction” tool. Destination Grid [raster] A grid that encodes the destination zone that may receive flow from upslope. This grid must be 1 inside the zone y and 0 over the rest of the domain. 612 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Output Upslope Dependence Grid [raster] A grid quantifing the amount each source point in the do- main contributes to the zone defined by the destination grid. Console usage processing.runalg(’taudem:dinfinityupslopedependence’,-ang,-dg,-dep) See also Slope Average Down Description This tool computes slope in a D8 downslope direction averaged over a user selected distance. Distance should be specified in horizontal map units. Parameters D8 Flow Direction Grid [raster] This input is a grid of flow directions that are encoded using the D8 method where all flow from a cells goes to a single neighboring cell in the direction of steepest descent.This grid can be obtained as the output of the “D8 Flow Directions” tool. Pit Filled Elevation Grid [raster] This input is a grid of elevation values. As a general rule, it is recommended that you use a grid of elevation values that have had the pits removed for this input. Pits are generally taken to be artifacts that interfere with the analysis of flow across them. This grid can be obtained as the output of the “Pit Remove” tool, in which case it contains elevation values where the pits have been filled to the point where they just drain. Downslope Distance [number] Input parameter of downslope distance over which to calculate the slope (in horizontal map units). Default: 50 Outputs Slope Average Down Grid [raster] This output is a grid of slopes calculated in the D8 downslope direc- tion, averaged over the selected distance. Console usage processing.runalg(’taudem:slopeaveragedown’,-p,-fel,-dn,-slpd) 18.8. TauDEM algorithm provider 613 QGIS User Guide, Release 2.6 See also Slope Over Area Ratio Description Calculates the ratio of the slope to the specific catchment area (contributing area). This is algebraically related to the more common ln(a/tan beta) wetness index, but contributing area is in the denominator to avoid divide by 0 errors when slope is 0. Parameters Slope Grid [raster] A grid of slope. This grid can be generated using ether the “D8 Flow Directions” tool or the “D-Infinity Flow Directions” tool. Specific Catchment Area Grid [raster] A grid giving the contributing area value for each cell taken as its own contribution plus the contribution from upslope neighbors that drain in to it. Contributing area is counted in terms of the number of grid cells (or summation of weights). This grid can be generated using either the “D8 Contributing Area” tool or the “D-Infinity Contributing Area” tool. Outputs Slope Divided By Area Ratio Grid [raster] A grid of the ratio of slope to specific catchment area (contributing area). This is algebraically related to the more common ln(a/tan beta) wetness index, but contributing area is in the denominator to avoid divide by 0 errors when slope is 0. Console usage processing.runalg(’taudem:slopeoverarearatio’,-slp,-sca,-sar) See also . 18.8.3 Stream Network Analysis D8 Extreme Upslope Value Description Evaluates the extreme (either maximum or minimum) upslope value from an input grid based on the D8 flow model. This is intended initially for use in stream raster generation to identify a threshold of the slope times area product that results in an optimum (according to drop analysis) stream network. If the optional outlet point shapefile is used, only the outlet cells and the cells upslope (by the D8 flow model) of them are in the domain to be evaluated. By default, the tool checks for edge contamination. This is defined as the possibility that a result may be underes- timated due to grid cells outside of the domain not being counted. This occurs when drainage is inwards from the boundaries or areas with “no data” values for elevation. The algorithm recognizes this and reports “no data” for the result for these grid cells. It is common to see streaks of “no data” values extending inwards from boundaries along flow paths that enter the domain at a boundary. This is the desired effect and indicates that the result for these grid cells is unknown due to it being dependent on terrain outside of the domain of data available. Edge 614 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 contamination checking may be turned off in cases where you know this is not an issue or want to ignore these problems, if for example, the DEM has been clipped along a watershed outline. Parameters D8 Flow Directions Grid [raster] A grid of D8 flow directions which are defined, for each cell, as the direction of the one of its eight adjacent or diagonal neighbors with the steepest downward slope. This grid can be obtained as the output of the “D8 Flow Directions” tool. Upslope Values Grid [raster] This is the grid of values of which the maximum or minimum upslope value is selected. The values most commonly used are the slope times area product needed when generating stream rasters according to drop analysis. Outlets Shapefile [vector: point] Optional. A point shape file defining outlets of interest. If this input file is used, only the area upslope of these outlets will be evaluated by the tool. Check for edge contamination [boolean] A flag that indicates whether the tool should check for edge contamination. Default: True Use max upslope value [boolean] A flag to indicate whether the maximum or minimum upslope value is to be calculated. Default: True Outputs Extereme Upslope Values Grid [raster] A grid of the maximum/minimum upslope values. Console usage processing.runalg(’taudem:d8extremeupslopevalue’,-p,-sa,-o,-nc,-min,-ssa) See also Length Area Stream Source Description Creates an indicator grid (1, 0) that evaluates A >= (M)(Ly) based on upslope path length, D8 contributing area grid inputs, and parameters M and y. This grid indicates likely stream source grid cells. This is an exper- imental method with theoretical basis in Hack’s law which states that for streams L ~ A 0.6. However for hillslopes with parallel flow L ~ A. So a transition from hillslopes to streams may be represented by L ~ A 0.8 suggesting identifying grid cells as stream cells if A > M (L (1/0.8)). Parameters Length Grid [raster] A grid of the maximum upslope length for each cell. This is calculated as the length of the flow path from the furthest cell that drains to each cell. Length is measured between cell centers taking into account cell size and whether the direction is adjacent or diagonal. It is this length (L) that is used in the formula, A >(M)(Ly), to determine which cells are considered stream cells. This grid can be obtained as an output from the “Grid Network” tool. 18.8. TauDEM algorithm provider 615 QGIS User Guide, Release 2.6 Contributing Area Grid [raster] A grid of contributing area values for each cell that were calculated us- ing the D8 algorithm. The contributing area for a cell is the sum of its own contribution plus the contribution from all upslope neighbors that drain to it, measured as a number of cells. This grid is typically obtained as the output of the “D8 Contributing Area” tool. In this tool, it is the contributing area (A) that is compared in the formula A > (M)(Ly) to determine the transition to a stream. Threshold [number] The multiplier threshold (M) parameter which is used in the formula: A > (M)(Ly), to identify the beginning of streams. Default: 0.03 Exponent [number] The exponent (y) parameter which is used in the formula: A > (M)(Ly), to identify the beginning of streams. In branching systems, Hack’s law uggests that L = 1/M A(1/y) with 1/y = 0.6 (or 0.56) (y about 1.7). In parallel flow systems L is proportional to A(y about 1). This method tries to identify the transition between these two paradigms by using an exponent y somewhere in between (y about 1.3). Default: 1.3 Outputs Stream Source Grid [raster] An indicator grid (1,0) that evaluates A >= (M)(L^y), based on the maximum upslope path length, the D8 contributing area grid inputs, and parameters M and y. This grid indicates likely stream source grid cells. Console usage processing.runalg(’taudem:lengthareastreamsource’, length_grid, contrib_area_grid, threshold, exponent, stream_source_grid) See also Move Outlets To Streams Description Moves outlet points that are not aligned with a stream cell from a stream raster grid, downslope along the D8 flow direction until a stream raster cell is encountered, the “max_dist” number of grid cells are examined, or the flow path exits the domain (i.e. a “no data” value is encountered for the D8 flow direction). The output file is a new outlets shapefile where each point has been moved to coincide with the stream raster grid, if possible. A field “dist_moved” is added to the new outlets shapefile to indicate the changes made to each point. Points that are already on a stream cell are not moved and their “dist_moved” field is assigned a value 0. Points that are initially not on a stream cell are moved by sliding them downslope along the D8 flow direction until one of the following occurs: a) A stream raster grid cell is encountered before traversing the “max_dist” number of grid cells. In which case, the point is moved and the “dist_moved” field is assigned a value indicating how many grid cells the point was moved. b) More than the “max_number” of grid cells are traversed, or c) the traversal ends up going out of the domain (i.e., a “no data” D8 flow direction value is encountered). In which case, the point is not moved and the “dist_moved” field is assigned a value of -1. Parameters D8 Flow Direction Grid [raster] A grid of D8 flow directions which are defined, for each cell, as the direction of the one of its eight adjacent or diagonal neighbors with the steepest downward slope. This grid can be obtained as the output of the “D8 Flow Directions” tool. 616 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Stream Raster Grid [raster] This output is an indicator grid (1, 0) that indicates the location of streams, with a value of 1 for each of the stream cells and 0 for the remainder of the cells. This file is produced by several different tools in the “Stream Network Analysis” toolset. Outlets Shapefile [vector: point] A point shape file defining points of interest or outlets that should ide- ally be located on a stream, but may not be exactly on the stream due to the fact that the shapefile point locations may not have been accurately registered with respect to the stream raster grid. Maximum Number of Grid Cells to traverse [number] This input paramater is the maximum number of grid cells that the points in the input outlet shapefile will be moved before they are saved to the output outlet shapefile. Default: 50 Outputs Output Outlet Shapefile [vector] A point shape file defining points of interest or outlets. This file has one point in it for each point in the input outlet shapefile. If the original point was located on a stream, then the point was not moved. If the origianl point was not on a stream, the point was moved downslope according to the D8 flow direction until it reached a stream or the maximum distance had been reached. This file has an additional field “dist_moved” added to it which is the number of cells that the point was moved. This field is 0 if the cell was originally on a stream, -1 if it was not moved becuase there was not a stream within the maximum distance, or some positive value if it was moved. Console usage processing.runalg(’taudem:moveoutletstostreams’,-p,-src,-o,-md,-om) See also Peuker Douglas Description Creates an indicator grid (1, 0) of upward curved grid cells according to the Peuker and Douglas algorithm. With this tool, the DEM is first smoothed by a kernel with weights at the center, sides, and diagonals. The Peuker and Douglas (1975) method (also explained in Band, 1986), is then used to identify upwardly curving grid cells. This technique flags the entire grid, then examines in a single pass each quadrant of 4 grid cells, and unflags the highest. The remaining flagged cells are deemed “upwardly curved”, and when viewed, resemble a channel network. This proto-channel network generally lacks connectivity and requires thinning, issues that were discussed in detail by Band (1986). Parameters Elevation Grid [raster] A grid of elevation values. This is usually the output of the “Pit Remove” tool, in which case it is elevations with pits removed. Center Smoothing Weight [number] The center weight parameter used by a kernel to smooth the DEM before the tool identifies upwardly curved grid cells. Default: 0.4 Side Smoothing Weight [number] The side weight parameter used by a kernel to smooth the DEM before the tool identifies upwardly curved grid cells. Default: 0.1 18.8. TauDEM algorithm provider 617 QGIS User Guide, Release 2.6 Diagonal Smoothing Weight [number] The diagonal weight parameter used by a kernel to smooth the DEM before the tool identifies upwardly curved grid cells. Default: 0.05 Outputs Stream Source Grid [raster] An indicator grid (1, 0) of upward curved grid cells according to the Peuker and Douglas algorithm, and if viewed, resembles a channel network. This proto-channel network generally lacks connectivity and requires thinning, issues that were discussed in detail by Band (1986). Console usage processing.runalg(’taudem:peukerdouglas’, elevation_grid, center_weight, side_weight, diagonal_weight, stream_source_grid) See also • Band, L. E., (1986), “Topographic partition of watersheds with digital elevation models”, Water Resources Research, 22(1): 15-24. • Peuker, T. K. and D. H. Douglas, (1975), “Detection of surface-specific points by local parallel processing of discrete terrain elevation data”, Comput. Graphics Image Process., 4: 375-387. Slope Area Combination Description Creates a grid of slope-area values = (Sm) (An) based on slope and specific catchment area grid inputs, and parameters m and n. This tool is intended for use as part of the slope-area stream raster delineation method. Parameters Slope Grid [raster] This input is a grid of slope values. This grid can be obtained from the “D-Infinity Flow Directions” tool. Contributing Area Grid [raster] A grid giving the specific catchment area for each cell taken as its own contribution (grid cell length or summation of weights) plus the proportional contribution from upslope neighbors that drain in to it. This grid is typically obtained from the “D-Infinity Contributing Area” tool. Slope Exponent [number] The slope exponent (m) parameter which will be used in the formula: (Sm)(An), that is used to create the slope-area grid. Default: 2 Area Exponent [number] The area exponent (n) parameter which will be used in the formula: (Sm)(An), that is used to create the slope-area grid. Default: 1 Outputs Slope Area Grid [raster] A grid of slope-area values = (Sm)(An) calculated from the slope grid, specific catchment area grid, m slope exponent parameter, and n area exponent parameter. 618 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Console usage processing.runalg(’taudem:slopeareacombination’, slope_grid, area_grid, slope_exponent, area_exponent, slope_area_grid) See also Stream Definition By Threshold Description Operates on any grid and outputs an indicator (1, 0) grid identifing cells with input values >= the threshold value. The standard use is to use an accumulated source area grid to as the input grid to generate a stream raster grid as the output. If you use the optional input mask grid, it limits the domain being evaluated to cells with mask values >= 0. When you use a D-infinity contributing area grid (*sca) as the mask grid, it functions as an edge contamination mask. The threshold logic is: src = ((ssa >= thresh) & (mask >= s0)) ? 1:0 Parameters Accumulated Stream Source Grid [raster] This grid nominally accumulates some characteristic or combination of characteristics of the watershed. The exact characteristic(s) varies depending on the stream network raster algorithm being used. This grid needs to have the property that grid cell values are monoton- ically increasing downslope along D8 flow directions, so that the resulting stream network is continuous. While this grid is often from an accumulation, other sources such as a maximum upslope function will also produce a suitable grid. Threshold [number] This parameter is compared to the value in the Accumulated Stream Source grid (*ssa) to determine if the cell should be considered a stream cell. Streams are identified as grid cells for which ssa value is >= this threshold. Default: 100 Mask Grid [raster] Optional. This optional input is a grid that is used to mask the domain of interest and output is only provided where this grid is >= 0. A common use of this input is to use a D-Infinity contributing area grid as the mask so that the delineated stream network is constrained to areas where D-infinity contributing area is available, replicating the functionality of an edge contamination mask. Outputs Stream Raster Grid [raster] This is an indicator grid (1, 0) that indicates the location of streams, with a value of 1 for each of the stream cells and 0 for the remainder of the cells. Console usage processing.runalg(’taudem:streamdefinitionbythreshold’,-ssa,-thresh,-mask,-src) 18.8. TauDEM algorithm provider 619 QGIS User Guide, Release 2.6 See also Stream Drop Analysis Description Applies a series of thresholds (determined from the input parameters) to the input accumulated stream source grid (*ssa) grid and outputs the results in the *drp.txt file the stream drop statistics table. This function is designed to aid in the determination of a geomorphologically objective threshold to be used to delineate streams. Drop Analysis attempts to select the right threshold automatically by evaluating a stream network for a range of thresholds and examining the constant drop property of the resulting Strahler streams. Basically it asks the question: Is the mean stream drop for first order streams statistically different from the mean stream drop for higher order streams, using a T-test. Stream drop is the difference in elevation from the beginning to the end of a stream defined as the sequence of links of the same stream order. If the T-test shows a significant difference then the stream network does not obey this “law” so a larger threshold needs to be chosen. The smallest threshold for which the T-test does not show a significant difference gives the highest resolution stream network that obeys the constant stream drop “law” from geomorphology, and is the threshold chosen for the “objective” or automatic mapping of streams from the DEM. This function can be used in the development of stream network rasters, where the exact watershed characteristic(s) that were accumulated in the accumulated stream source grid vary based on the method being used to determine the stream network raster. The constant stream drop “law” was identified by Broscoe (1959). For the science behind using this to determine a stream delineation threshold, see Tarboton et al. (1991, 1992), Tarboton and Ames (2001). Parameters D8 Contributing Area Grid [raster] A grid of contributing area values for each cell that were calcu- lated using the D8 algorithm. The contributing area for a cell is the sum of its own contribution plus the contribution from all upslope neighbors that drain to it, measured as a number of cells or the sum of weight loadings. This grid can be obtained as the output of the “D8 Contributing Area” tool. This grid is used in the evaluation of drainage density reported in the stream drop table. D8 Flow Direction Grid [raster] A grid of D8 flow directions which are defined, for each cell, as the direction of the one of its eight adjacent or diagonal neighbors with the steepest downward slope. This grid can be obtained as the output of the “D8 Flow Directions” tool. Pit Filled Elevation Grid [raster] A grid of elevation values. This is usually the output of the “Pit Remove” tool, in which case it is elevations with pits removed. Accumulated Stream Source Grid [raster] This grid must be monotonically increasing along the downslope D8 flow directions. It it compared to a series of thresholds to determine the beginning of the streams. It is often generated by accumulating some characteristic or combination of characteristics of the watershed with the “D8 Contributing Area” tool, or using the maximum option of the “D8 Flow Path Extreme” tool. The exact method varies depending on the algorithm being used. Outlets Shapefile [vector: point] A point shapefile defining the outlets upstream of which drop analysis is performed. 620 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Minimum Threshold [number] This parameter is the lowest end of the range searched for possible threshold values using drop analysis. This technique looks for the smallest threshold in the range where the absolute value of the t-statistic is less than 2. For the science behind the drop analysis see Tarboton et al. (1991, 1992), Tarboton and Ames (2001). Default: 5 Maximum Threshold [number] This parameter is the highest end of the range searched for possible threshold values using drop analysis. This technique looks for the smallest threshold in the range where the absolute value of the t-statistic is less than 2. For the science behind the drop analysis see Tarboton et al. (1991, 1992), Tarboton and Ames (2001). Default: 500 Number of Threshold Values [number] The parameter is the number of steps to divide the search range into when looking for possible threshold values using drop analysis. This technique looks for the smallest threshold in the range where the absolute value of the t-statistic is less than 2. For the science behind the drop analysis see Tarboton et al. (1991, 1992), Tarboton and Ames (2001). Default: 10 Spacing for Threshold Values [selection] This parameter indicates whether logarithmic or linear spacing should be used when looking for possible threshold values using drop ananlysis. Options: • 0 — Logarithmic • 1 — Linear Default: 0 Outputs D-Infinity Drop to Stream Grid [file] This is a comma delimited text file with the following header line: :: Threshold,DrainDen,NoFirstOrd,NoHighOrd,MeanDFirstOrd,MeanDHighOrd,StdDevFirstOrd,StdDevHighOrd,T The file then contains one line of data for each threshold value examined, and then a summary line that indicates the optimum threshold value. This technique looks for the smallest threshold in the range where the absolute value of the t-statistic is less than 2. For the science behind the drop analysis, see Tarboton et al. (1991, 1992), Tarboton and Ames (2001). Console usage processing.runalg(’taudem:streamdropanalysis’, d8_contrib_area_grid, d8_flow_dir_grid, pit_filled_grid, accum_stream_source_grid, outlets_shape, min_treshold, max_threshold, treshold_num, step_type, drop_analysis_file) See also • Broscoe, A. J., (1959), “Quantitative analysis of longitudinal stream profiles of small watersheds”, Office of Naval Research, Project NR 389-042, Technical Report No. 18, Department of Geology, Columbia University, New York. • Tarboton, D. G., R. L. Bras and I. Rodriguez-Iturbe, (1991), “On the Extraction of Channel Networks from Digital Elevation Data”, Hydrologic Processes, 5(1): 81-100. • Tarboton, D. G., R. L. Bras and I. Rodriguez-Iturbe, (1992), “A Physical Basis for Drainage Density”, Geomorphology, 5(1/2): 59-76. • Tarboton, D. G. and D. P. Ames, (2001), “Advances in the mapping of flow networks from digital ele- vation data”, World Water and Environmental Resources Congress, Orlando, Florida, May 20-24, ASCE, http://www.engineering.usu.edu/dtarb/asce2001.pdf. 18.8. TauDEM algorithm provider 621 QGIS User Guide, Release 2.6 Stream Reach and Watershed Description This tool produces a vector network and shapefile from the stream raster grid. The flow direction grid is used to connect flow paths along the stream raster. The Strahler order of each stream segment is computed. The subwatershed draining to each stream segment (reach) is also delineated and labeled with the value identifier that corresponds to the WSNO (watershed number) attribute in the Stream Reach Shapefile. This tool orders the stream network according to the Strahler ordering system. Streams that don’t have any other streams draining in to them are order 1. When two stream reaches of different order join the order of the downstream reach is the order of the highest incoming reach. When two reaches of equal order join the downstream reach order is increased by 1. When more than two reaches join the downstream reach order is calculated as the maximum of the highest incoming reach order or the second highest incoming reach order + 1. This generalizes the common definition to cases where more than two reaches join at a point. The network topological connectivity is stored in the Stream Network Tree file, and coordinates and attributes from each grid cell along the network are stored in the Network Coordinates file. The stream raster grid is used as the source for the stream network, and the flow direction grid is used to trace connections within the stream network. Elevations and contributing area are used to determine the elevation and contributing area attributes in the network coordinate file. Points in the outlets shapefile are used to logically split stream reaches to facilitate representing watersheds upstream and downstream of monitoring points. The program uses the attribute field “id” in the outlets shapefile as identifiers in the Network Tree file. This tool then translates the text file vector network representation in the Network Tree and Coordinates files into a shapefile. Further attributes are also evaluated. The program has an option to delineate a single watershed by representing the entire area draining to the Stream Network as a single value in the output watershed grid. Parameters Pit Filled Elevation Grid [raster] A grid of elevation values. This is usually the output of the “Pit Remove” tool, in which case it is elevations with pits removed. D8 Flow Direction Grid [raster] A grid of D8 flow directions which are defined, for each cell, as the direction of the one of its eight adjacent or diagonal neighbors with the steepest downward slope. This grid can be obtained as the output of the “D8 Flow Directions” tool. D8 Drainage Area [raster] A grid giving the contributing area value in terms of the number of grid cells (or the summation of weights) for each cell taken as its own contribution plus the contribution from upslope neighbors that drain in to it using the D8 algorithm. This is usually the output of the “D8 Contributing Area” tool and is used to determine the contributing area attribute in the Network Coordinate file. Stream Raster Grid [raster] An indicator grid indicating streams, by using a grid cell value of 1 on streams and 0 off streams. Several of the “Stream Network Analysis” tools produce this type of grid. The Stream Raster Grid is used as the source for the stream network. Outlets Shapefile as Network Nodes [vector: point] Optional. A point shape file defining points of interest. If this file is used, the tool will only deliiniate the stream network upstream of these outlets. Additionally, points in the Outlets Shapefile are used to logically split stream reaches to facilitate representing watersheds upstream and downstream of monitoring points. This tool REQUIRES THAT THERE BE an integer attribute field “id” in the Outlets Shapefile, because the “id” values are used as identifiers in the Network Tree file. Delineate Single Watershed [boolean] This option causes the tool to delineate a single watershed by representing the entire area draining to the Stream Network as a single value in the output watershed grid. Otherwise a seperate watershed is delineated for each stream reach. Default is False (seperate watershed). Default: False 622 Chapter 18. Processing providers and algorithms QGIS User Guide, Release 2.6 Outputs Stream Order Grid [raster] The Stream Order Grid has cells values of streams ordered according to the Strahler order system. The Strahler ordering system defines order 1 streams as stream reaches that don’t have any other reaches draining in to them. When two stream reaches of different order join the order of the downstream reach is the order of the highest incoming reach. When two reaches of equal order join the downstream reach order is increased by 1. When more than two reaches join the downstream reach order is calculated as the maximum of the highest incoming reach order or the second highest incoming reach order + 1. This generalizes the common definition to cases where more than two flow paths reaches join at a point. Watershed Grid [raster] This output grid identified each reach watershed with a unique ID number, or in the case where the delineate single watershed option was checked, the entire area draining to the stream network is identified with a single ID. Stream Reach Shapefile [vector] This output is a polyline shapefile giving the links in a stream network. The columns in the attribute table are: • LINKNO — Link Number. A unique number associated with each link (segment of channel between junctions). This is arbitrary and will vary depending on number of processes used • DSLINKNO — Link Number of the downstream link. -1 indicates that this does not exist • USLINKNO1 — Link Number of first upstream link. (-1 indicates no link upstream, i.e. for a source link) • USLINKNO2 — Link Number of second upstream link. (-1 indicates no second link upstream, i.e. for a source link or an internal monitoring point where the reach is logically split but the network does not bifurcate) • DSNODEID — Node identifier for node at downstream end of stream reach. This identifier corre- sponds to the “id” attribute from the Outlets shapefile used to designate nodes • Order — Strahler Stream Order • Length — Length of the link. The units are the horizontal map units of the underlying DEM grid • Magnitude — Shreve Magnitude of the link. This is the total number of sources upstream • DS_Cont_Ar — Drainage area at the downstream end of the link. Generally this is one grid cell upstream of the downstream end because the drainage area at the downstream end grid cell includes the area of the stream being joined • Drop — Drop in elevation from the start to the end of the link • Slope — Average slope of the link (computed as drop/length) • Straight_L — Straight line distance from the start to the end of the link • US_Cont_Ar — Drainage area at the upstream end of the link • WSNO — Watershed number. Cross reference to the *w.shp and *w grid files giving the identifica- tion number of the watershed draining directly to the link • DOUT_END — Distance to the eventual outlet (i.e. the most downstream point in the stream network) from the downstream end of the link • DOUT_START — Distance to the eventual outlet from the upstream end of the link • DOUT_MID — Distance to the eventual outlet from the midpoint of the link Network Connectivity Tree [file] This output is a text file that details the network topological connec- tivity is stored in the Stream Network Tree file. Columns are as follows: • Link Number (Arbitrary — will vary depending on number of processes used) • Start Point Number in Network coordinates (*coord.dat) file (Indexed from 0) • End Point Number in Network coordinates (*coord.dat) file (Indexed from 0) 18.8. TauDEM algorithm provider 623 QGIS User Guide, Release 2.6 • Next (Downstream) Link Number. Points to Link Number. -1 indicates no links downstream, i.e. a terminal link • First Previous (Upstream) Link Number. Points to Link Number. -1 indicates no upstream links • Second Previous (Upstream) Link Numbers. Points to Link Number. -1 indicates no upstream links. Where only one previous link is -1, it indicates an internal monitoring point where the reach is logically split, but the network does not bifurcate • Strahler Order of Link • Monitoring point identifier at downstream end of link. -1 indicates downstream end is not a monitoring point • Network magnitude of the link, calculated as the number of upstream sources (following Shreve) Network Coordinates [file] This output is a text file that contains the coordinates and attributes of points along the stream network. Columns are as follows: • X coordinate • Y Coordinate • Distance along channels to the downstream end of a terminal link • Elevation • Contributing area Console usage processing.runalg(’taudem:streamreachandwatershed’,-fel,-p,-ad8,-src,-o,-sw,-ord,-w,-net,-tree,-coord) See also . 624 Chapter 18. Processing providers and algorithms CHAPTER 19 Print Composer With the Print Composer you can create nice maps and atlasses that can be printed or saved as PDF-file, an image or an SVG-file. This is a powerfull way to share geographical information produced with QGIS that can be included in reports or published. The Print Composer provides growing layout and printing capabilities. It allows you to add elements such as the QGIS map canvas, text labels, images, legends, scale bars, basic shapes, arrows, attribute tables and HTML frames. You can size, group, align and position each element and adjust the properties to create your layout. The layout can be printed or exported to image formats, PostScript, PDF or to SVG (export to SVG is not working properly with some recent Qt4 versions; you should try and check individually on your system). You can save the layout as a template and load it again in another session. Finally, generating several maps based on a template can be done through the atlas generator. See a list of tools in table_composer_1: 625 QGIS User Guide, Release 2.6 Icon Purpose Icon Purpose Save Project New Composer Duplicate Composer Composer Manager Load from template Save as template Print or export as PostScript Export to an image format Export print composition to SVG Export as PDF Revert last change Restore last change Zoom to full extent Zoom to 100% Zoom in Zoom out Refresh View Pan Zoom to specific region Select/Move item in print composition Move content within an item Add new map from QGIS map canvas Add image to print composition Add label to print composition Add new legend to print composition Add scale bar to print composition Add basic shape to print composition Add arrow to print composition Add attribute table to print composition Add an HTML frame Group items of print composition Ungroup items of print composition Lock Selected Items Unlock All items Raise selected items Lower selected items Move selected items to top Move selected items to bottom Align selected items left Align selected items right Align selected items center Align selected items center vertical Align selected items top Align selected items bottom Preview Atlas First Feature Previous Feature Next Feature Last feature Print Atlas Export Atlas as Image Atlas Settings Table Composer 1: Print Composer Tools All Print Composer tools are available in menus and as icons in a toolbar. The toolbar can be switched off and on using the right mouse button over the toolbar. 19.1 First steps 19.1.1 Open a new Print Composer Template Before you start to work with the Print Composer, you need to load some raster and vector layers in the QGIS map canvas and adapt their properties to suit your own convenience. After everything is rendered and symbolized to your liking, click the New Print Composer icon in the toolbar or choose File → New Print Composer. You will 626 Chapter 19. Print Composer QGIS User Guide, Release 2.6 be prompted to choose a title for the new Composer. 19.1.2 Overview of the Print Composer Opening the Print Composer provides you with a blank canvas that represents the paper surface when using the print option. Initially you find buttons on the left beside the canvas to add map composer items; the current QGIS map canvas, text labels, images, legends, scale bars, basic shapes, arrows, attribute tables and HTML frames. In this toolbar you also find toolbar buttons to navigate, zoom in on an area and pan the view on the composer and toolbar buttons to select a map composer item and to move the contents of the map item. Figure_composer_overview shows the initial view of the Print Composer before any elements are added. Figure 19.1: Print Composer On the right beside the canvas you find two panels. The upper panel holds the tabs Items and Command History and the lower panel holds the tabs Composition, Item properties and Atlas generation. • The Items tab provides a list of all map composer items added to the canvas. • The Command history tab displays a history of all changes applied to the Print Composer layout. With a mouse click, it is possible to undo and redo layout steps back and forth to a certain status. • The Composition tab allows you to set paper size, orientation, the page background, number of pages and print quality for the output file in dpi. Furthermore, you can also activate the Print as raster checkbox. This means all items will be converted to raster before printing or saving as PostScript or PDF. In this tab, you can also customize settings for grid and smart guides. 19.1. First steps 627 QGIS User Guide, Release 2.6 • The Item Properties tab displays the properties for the selected item. Click the Select/Move item icon to select an item (e.g., legend, scale bar or label) on the canvas. Then click the Item Properties tab and customize the settings for the selected item. • The Atlas generation tab allows you to enable the generation of an atlas for the current Composer and gives access to its parameters. • Finally, you can save your print composition with the Save Project button. In the bottom part of the Print Composer window, you can find a status bar with mouse position, current page number and a combo box to set the zoom level. You can add multiple elements to the Composer. It is also possible to have more than one map view or legend or scale bar in the Print Composer canvas, on one or several pages. Each element has its own properties and, in the case of the map, its own extent. If you want to remove any elements from the Composer canvas you can do that with the Delete or the Backspace key. Navigation tools To navigate in the canvas layout, the Print Composer provides some general tools: • Zoom in • Zoom out • Zoom to full extent • Zoom to 100% • Refresh the view (if you find the view in an inconsistent state) • Pan composer • Marquee zoom mode (zoom to a specific region of the Composer) You can change the zoom level also using the mouse wheel or the combo box in the status bar. If you need to switch to pan mode while working in the Composer area, you can hold the Spacebar or the the mouse wheel. With Ctrl+Spacebar, you can temporarily switch to marquee zoom mode, and with Ctrl+Shift+Spacebar, to zoom out mode. 19.1.3 Sample Session To demonstrate how to create a map please follow the next instructions. 1. On the left site, select the Add new map toolbar button and draw a rectangle on the canvas holding down the left mouse button. Inside the drawn rectangle the QGIS map view to the canvas. 2. Select the Add new scalebar toolbar button and place the map item with the left mouse button on the Print Composer canvas. A scalebar will be added to the canvas. 3. Select the Add new legend toolbar button and draw a rectangle on the canvas holding down the left mouse button. Inside the drawn rectangle the legend will be drawn. 4. Select the Select/Move item icon to select the map on the canvas and move it a bit. 5. While the map item is still selected you can also change the size of the map item. Click while holding down the left mouse button, in a white little rectangle in one of the corners of the map item and draw it to a new location to change it’s size. 628 Chapter 19. Print Composer QGIS User Guide, Release 2.6 6. Click the Item Properties tab on the left lower panel and find the setting for the orientation. Change it the value of the setting Map orientation to ‘15.00° ‘. You should see the orientation of the map item change. 7. Finally, you can save your print composition with the Save Project button. 19.1.4 Print Composer Options From Settings → Composer Options you can set some options that will be used as default during your work. • Compositions defaults let you specify the default font to use. • With Grid appearance, you can set the grid style and its color. • Grid defaults defines spacing, offset and tolerance of the grid. There are three types of grid: Dots, Solid lines and Crosses. • Guide defaults defines the tolerance for the guides. 19.1.5 Composition tab — General composition setup In the Composition tab, you can define the global settings of your composition. • You can choose one of the Presets for your paper sheet, or enter your custom width and height. • Composition can now be divided into several pages. For instance, a first page can show a map canvas, and a second page can show the attribute table associated with a layer, while a third one shows an HTML frame linking to your organization website. Set the Number of pages to the desired value. You can choose the page Orientation and its Exported resolution. When checked, print as raster means all elements will be rasterized before printing or saving as PostScript or PDF. • Grid lets you customize grid settings like spacings, offsets and tolerance to your need. • In Snap to alignments, you can change the Tolerance, which is the maximum distance below which an item is snapped to smart guides. Snap to grid and/or to smart guides can be enabled from the View menu. In this menu, you can also hide or show the grid and smart guides. 19.1.6 Composer items common options Composer items have a set of common properties you will find on the bottom of the Item Properties tab: Position and size, Rotation, Frame, Background, Item ID and Rendering (See figure_composer_common_1). • The Position and size dialog lets you define size and position of the frame that contains the item. You can also choose which Reference point will be set at the X and Y coordinates previously defined. • The Rotation sets the rotation of the element (in degrees). • The Frame shows or hides the frame around the label. Click on the [Color] and [Thickness] buttons to adjust those properties. • The Background enables or disables a background color. Click on the [Color...] button to display a dialog where you can pick a color or choose from a custom setting. Transparency can also be adjusted throught the alpha field. • Use the Item ID to create a relationship to other Print Composer items. This is used with QGIS server and any potential web client. You can set an ID on an item (e.g., a map and a label), and then the web client can send data to set a property (e.g., label text) for that specific item. The GetProjectSettings command will list what items and which IDs are available in a layout. • Rendering mode can be selected in the option field. See Rendering_Mode. 19.1. First steps 629 QGIS User Guide, Release 2.6 Figure 19.2: Common Item properties Dialogs Note: • If you checked Use live-updating color chooser dialogs in the QGIS general options, the color button will update as soon as you choose a new color from Color Dialog windows. If not, you need to close the Color Dialog. • The Data defined override icon next to a field means that you can associate the field with data in the map item or use expressions. These are particularly helpful with atlas generation (See atlas_data_defined_overrides). 19.2 Rendering mode QGIS now allows advanced rendering for Composer items just like vector and raster layers. Figure 19.3: Rendering mode • Transparency : You can make the underlying item in the Composer visible with this tool. Use the slider to adapt the visibility of your item to your needs. You can also make a precise definition of the percentage of visibility in the the menu beside the slider. • Exclude item from exports: You can decide to make an item not visible in all exports. After activating this checkbox, the item will not be included in PDF’s, prints etc.. • Blending mode: You can achieve special rendering effects with these tools that you previously only may know from graphics programs. The pixels of your overlaying and underlaying items are mixed through the settings described below. 630 Chapter 19. Print Composer QGIS User Guide, Release 2.6 – Normal: This is the standard blend mode, which uses the alpha channel of the top pixel to blend with the pixel beneath it; the colors aren’t mixed. – Lighten: This selects the maximum of each component from the foreground and background pixels. Be aware that the results tend to be jagged and harsh. – Screen: Light pixels from the source are painted over the destination, while dark pixels are not. This mode is most useful for mixing the texture of one layer with another layer (e.g., you can use a hillshade to texture another layer). – Dodge: Dodge will brighten and saturate underlying pixels based on the lightness of the top pixel. So, brighter top pixels cause the saturation and brightness of the underlying pixels to increase. This works best if the top pixels aren’t too bright; otherwise the effect is too extreme. – Addition: This blend mode simply adds pixel values of one layer with pixel values of the other. In case of values above 1 (as in the case of RGB), white is displayed. This mode is suitable for highlighting features. – Darken: This creates a resultant pixel that retains the smallest components of the foreground and background pixels. Like lighten, the results tend to be jagged and harsh. – Multiply: Here, the numbers for each pixel of the top layer are multiplied with the numbers for the corresponding pixel of the bottom layer. The results are darker pictures. – Burn: Darker colors in the top layer cause the underlying layers to darken. Burn can be used to tweak and colorise underlying layers. – Overlay: This mode combines the multiply and screen blending modes. In the resulting picture, light parts become lighter and dark parts become darker. – Soft light: This is very similar to overlay, but instead of using multiply/screen it uses color burn/dodge. This mode is supposed to emulate shining a soft light onto an image. – Hard light: Hard light is very similar to the overlay mode. It’s supposed to emulate projecting a very intense light onto an image. – Difference: Difference subtracts the top pixel from the bottom pixel, or the other way around, to always get a positive value. Blending with black produces no change, as the difference with all colors is zero. – Subtract: This blend mode simply subtracts pixel values of one layer with pixel values of the other. In case of negative values, black is displayed. 19.3 Composer Items 19.3.1 The Map item Click on the Add new map toolbar button in the Print Composer toolbar to add the QGIS map canvas. Now, drag a rectangle onto the Composer canvas with the left mouse button to add the map. To display the current map, you can choose between three different modes in the map Item Properties tab: • Rectangle is the default setting. It only displays an empty box with a message ‘Map will be printed here’. • Cache renders the map in the current screen resolution. If you zoom the Composer window in or out, the map is not rendered again but the image will be scaled. • Render means that if you zoom the Composer window in or out, the map will be rendered again, but for space reasons, only up to a maximum resolution. Cache is the default preview mode for newly added Print Composer maps. 19.3. Composer Items 631 QGIS User Guide, Release 2.6 You can resize the map element by clicking on the Select/Move item button, selecting the element, and dragging one of the blue handles in the corner of the map. With the map selected, you can now adapt more properties in the map Item Properties tab. To move layers within the map element, select the map element, click the Move item content icon and move the layers within the map item frame with the left mouse button. After you have found the right place for an item, you can lock the item position within the Print Composer canvas. Select the map item and use the toolbar Lock Selected Items or the Items tab to Lock the item. A locked item can only be selected using the Items tab. Once selected you can use the Items tab to unlock individual items. The Unlock All Items icon will unlock all locked composer items. Main properties The Main properties dialog of the map Item Properties tab provides the following functionalities (see fig- ure_composer_map_1): Figure 19.4: Map Item properties Tab • The Preview area allows you to define the preview modes ‘Rectangle’, ‘Cache’ and ‘Render’, as described above. If you change the view on the QGIS map canvas by changing vector or raster properties, you can update the Print Composer view by selecting the map element in the Print Composer and clicking the [Update preview] button. • The field Scale sets a manual scale. • The field Rotation allows you to rotate the map element content clockwise in degrees. Note that a coordinate frame can only be added with the default value 0. • Draw map canvas items lets you show annotations that may be placed on the map canvas in the main QGIS window. • You can choose to lock the layers shown on a map item. Check Lock layers for map item. After this is checked, any layer that would be displayed or hidden in the main QGIS window will not appear or be 632 Chapter 19. Print Composer QGIS User Guide, Release 2.6 hidden in the map item of the Composer. But style and labels of a locked layer are still refreshed according to the main QGIS interface. • The button allows you to add quickly all the presets views you have prepared in QGIS. Clicking on the button you will see the list of all the preset views: just select the preset you want to display. The map canvas will automatically lock the preset layers by enabling the Lock layers for map item: if you want to unselect the preset, just uncheck the and press on the button. See Map Legend to find out how to create presets views. Extents The Extents dialog of the map item tab provides the following functionalities (see figure_composer_map_2): Figure 19.5: Map Extents Dialog • The Map extents area allows you to specify the map extent using X and Y min/max values and by clicking the [Set to map canvas extent] button. This button sets the map extent of the composer map item to the extent of the current map view in the main QGIS application. The button [View extent in map canvas] does exactly the opposite, it updates the extent of the map view in the QGIS application to the extent of the composer map item. If you change the view on the QGIS map canvas by changing vector or raster properties, you can update the Print Composer view by selecting the map element in the Print Composer and clicking the [Update preview] button in the map Item Properties tab (see figure_composer_map_1). Grids The Grids dialog of the map Item Properties tab provides the the possibility to add several grids to a map item. • With the plus and minus button you can add or remove a selected grid. • With the up and down button you can move a grid in the list and set the drawing priority. When you double click on the added grid you can give it another name. Figure 19.6: Map Grids Dialog 19.3. Composer Items 633 QGIS User Guide, Release 2.6 After you have added a grid, you can active the checkbox Show grid to overlay a grid onto the map element. Expand this option to provides a lot of configuration options, see Figure_composer_map_4. Figure 19.7: Draw Grid Dialog As grid type, you can specify to use a solid line or cross. Symbology of the grid can be chosen. See section Rendering_Mode. Furthermore, you can define an interval in the X and Y directions, an X and Y offset, and the width used for the cross or line grid type. Figure 19.8: Grid Frame Dialog • There are different options to style the frame that holds the map. Following options are available: No Frame, Zebra, Interior ticks, Exterior ticks, Interior and Exterior ticks and Lineborder. • Advanced rendering mode is also available for grids (see section Rendering_mode). • The Draw coordinates checkbox allows you to add coordinates to the map frame. The annotation can be drawn inside or outside the map frame. The annotation direction can be defined as horizontal, vertical, horizontal and vertical, or boundary direction, for each border individually. Units can be in meters or in degrees. Finally, you can define the grid color, the annotation font, the annotation distance from the map frame and the precision of the drawn coordinates. Overviews The Overviews dialog of the map Item Properties tab provides the following functionalities: 634 Chapter 19. Print Composer QGIS User Guide, Release 2.6 Figure 19.9: Grid Draw Coordinates dialog Figure 19.10: Map Overviews Dialog 19.3. Composer Items 635 QGIS User Guide, Release 2.6 You can choose to create an overview map, which shows the extents of the other map(s) that are available in the composer. First you need to create the map(s) you want to include in the overview map. Next you create the map you want to use as the overview map, just like a normal map. • With the plus and minus button you can add or remove an overview. • With the up and down button you can move an overview in the list and set the drawing priority. Open Overviews and press the green plus icon-button to add an overview. Initially this overview is named ‘Overview 1’ (see Figure_composer_map_7). You can change the name when you double-click on the overview item in the list named ‘Overview 1’ and change it to another name. When you select the overview item in the list you can customize it. • The Draw “” overview needs to be activated to draw the extent of selected map frame. • The Map frame combo list can be used to select the map item whose extents will be drawn on the present map item. • The Frame Style allows you to change the style of the overview frame. • The Blending mode allows you to set different transparency blend modes. See Rendering_Mode. • The Invert overview creates a mask around the extents when activated: the referenced map extents are shown clearly, whereas everything else is blended with the frame color. • The Center on overview puts the extent of the overview frame in the center of the overview map. You can only activate one overview item to center, when you have added several overviews. 19.3.2 The Label item To add a label, click the Add label icon, place the element with the left mouse button on the Print Composer canvas and position and customize its appearance in the label Item Properties tab. The Item Properties tab of a label item provides the following functionality for the label item (see Fig- ure_composer_label): Figure 19.11: Label Item properties Tab 636 Chapter 19. Print Composer QGIS User Guide, Release 2.6 Main properties • The main properties dialog is where the text (HTML or not) or the expression needed to fill the label is added to the Composer canvas. • Labels can be interpreted as HTML code: check Render as HTML. You can now insert a URL, a clickable image that links to a web page or something more complex. • You can also insert an expression. Click on [Insert an expression] to open a new dialog. Build an ex- pression by clicking the functions available in the left side of the panel. Two special categories can be useful, particularly associated with the atlas functionality: geometry functions and records functions. At the bottom, a preview of the expression is shown. • Define Font by clicking on the [Font...] button or a Font color selecting a color using the color selection tool. Alignment and Display • You can define the horizontal and vertical alignment in the Alignment zone. • In the Display tag, you can define a margin in mm. This is the margin from the edge of the composer item. 19.3.3 The Image item To add an image, click the Add image icon, place the element with the left mouse button on the Print Composer canvas and position and customize its appearance in the image Item Properties tab. The image Item Properties tab provides the following functionalities (see figure_composer_image_1): Figure 19.12: Image Item properties Tab 19.3. Composer Items 637 QGIS User Guide, Release 2.6 You first have to select the image you want to display. There are several ways to set the image source in the Main properties area. 1. Use the browse button of image source to select a file on your computer using the browse dialog. The browser will start in the SVG-libraries provided with QGIS. Besides SVG, you can also select other image formats like .png or .jpg. 2. You can enter the source directly in the image source text field. You can even provide a remote URL-address to an image. 3. From the Search directories area you can also select an image from loading preview.. to set the image source. 4. Use the data defined button to set the image source from a record or using a regular expression. With the Resize mode option, you can set how the image is displayed when the frame is changed, or choose to resize the frame of the image item so it matches the original size of the image. You can select one of the following modes: • Zoom: Enlarges the image to the frame while maintaining aspect ratio of picture. • Stretch: Stretches image to fit inside the frame, ignores aspect ratio. • Clip: Use this mode for raster images only, it sets the size of the image to original image size without scaling and the frame is used to clip the image, so only the part of the image inside the frame is visible. • Zoom and resize frame: Enlarges image to fit frame, then resizes frame to fit resultant image. • Resize frame to image size: Sets size of frame to match original size of image without scaling. Selected resize mode can disable the item options ‘Placement’ and ‘Image rotation’. The Image rotation is active for the resize mode ‘Zoom’ and ‘Clip’. With Placement you can select the position of the image inside it’s frame. The Search directories area allows you to add and remove directories with images in SVG format to the picture database. A preview of the pictures found in the selected directories is shown in a pane and can be used to select and set the image source. Images can be rotated with the Image rotation field. Activating the Sync with map checkbox synchronizes the rotation of a picture in the QGIS map canvas (i.e., a rotated north arrow) with the appropriate Print Composer image. It is also possible to select a north arrow directly. If you first select a north arrow image from Search directories and then use the browse button of the field Image source, you can now select one of the north arrow from the list as displayed in figure_composer_image_2. Note: Many of the north arrows do not have an ‘N’ added in the north arrow, this is done on purpose for languages that do not use an ‘N’ for North, so they can use another letter. 19.3.4 The Legend item To add a map legend, click the Add new legend icon, place the element with the left mouse button on the Print Composer canvas and position and customize the appearance in the legend Item Properties tab. The Item properties of a legend item tab provides the following functionalities (see figure_composer_legend_1): Main properties The Main properties dialog of the legend Item Properties tab provides the following functionalities (see fig- ure_composer_legend_2): In Main properties you can: 638 Chapter 19. Print Composer QGIS User Guide, Release 2.6 Figure 19.13: North arrows available for selection in provided SVG library Figure 19.14: Legend Item properties Tab Figure 19.15: Legend Main properties Dialog 19.3. Composer Items 639 QGIS User Guide, Release 2.6 • Change the title of the legend. • Set the title alignment to Left, Center or Right. • You can choose which Map item the current legend will refer to in the select list. • You can wrap the text of the legend title on a given character. Legend items The Legend items dialog of the legend Item Properties tab provides the following functionalities (see fig- ure_composer_legend_3): Figure 19.16: Legend Legend Items Dialog • The legend will be updated automatically if Auto-update is checked. When Auto-update is unchecked this will give you more control over the legend items. The icons below the legend items list will be activated. • The legend items window lists all legend items and allows you to change item order, group layers, remove and restore items in the list, edit layer names and add a filter. – The item order can be changed using the [Up] and [Down] buttons or with ‘drag-and-drop’ function- ality. The order can not be changed for WMS legend graphics. – Use the [Add group] button to add a legend group. – Use the [plus] and [minus] button to add or remove layers. – The [Edit] button is used to edit the layer-, groupname or title, first you need to select the legend item. – The [Sigma] button adds a feature count for each vector layer. – Use the [filter] button the filter the legend by map content, only the legend items visible in the map will be listed in the legend. After changing the symbology in the QGIS main window, you can click on [Update] to adapt the changes in the legend element of the Print Composer. Fonts, Columns, Symbol The Fonts, Columns and Symbol dialogs of the legend Item Properties tab provide the following functionalities (see figure_composer_legend_4): • You can change the font of the legend title, group, subgroup and item (layer) in the legend item. Click on a category button to open a Select font dialog. • You provide the labels with a Color using the advanced color picker, however the selected color will be given to all font items in the legen.. • Legend items can be arranged over several columns. Set the number of columns in the Count field. – Equal column widths sets how legend columns should be adjusted. 640 Chapter 19. Print Composer QGIS User Guide, Release 2.6 Figure 19.17: Legend Fonts, Columns, Symbol and Spacing Dialogs – The Split layers option allows a categorized or a graduated layer legend to be divided between columns. • You can change the width and height of the legend symbol in this dialog. WMS legendGraphic and Spacing The WMS legendGraphic and Spacing dialogs of the legend Item Properties tab provide the following functional- ities (see figure_composer_legend_5): Figure 19.18: WMS legendGraphic Dialogs When you have added a WMS layer and you insert a legend composer item, a request will be send to the WMS server to provide a WMS legend, This Legend will only be shown if the WMS server provides the GetLegend- Graphic capability. The WMS legend content will be provided as a raster image. 19.3. Composer Items 641 QGIS User Guide, Release 2.6 WMS legendGraphic is used to be able to adjust the Legend width and the legend hight of the WMS legend raster image. Spacing around title, group, subgroup, symbol, icon label, box space or column space can be customized through this dialog. 19.3.5 The Scale Bar item To add a scale bar, click the Add new scalebar icon, place the element with the left mouse button on the Print Composer canvas and position and customize the appearance in the scale bar Item Properties tab. The Item properties of a scale bar item tab provides the following functionalities (see fig- ure_composer_scalebar_1): Figure 19.19: Scale Bar Item properties Tab Main properties The Main properties dialog of the scale bar Item Properties tab provides the following functionalities (see fig- ure_composer_scalebar_2): Figure 19.20: Scale Bar Main properties Dialog • First, choose the map the scale bar will be attached to. • Then, choose the style of the scale bar. Six styles are available: – Single box and Double box styles, which contain one or two lines of boxes alternating colors. – Middle, Up or Down line ticks. – Numeric, where the scale ratio is printed (i.e., 1:50000). 642 Chapter 19. Print Composer QGIS User Guide, Release 2.6 Units and Segments The Units and Segments dialogs of the scale bar Item Properties tab provide the following functionalities (see figure_composer_scalebar_3): Figure 19.21: Scale Bar Units and Segments Dialogs In these two dialogs, you can set how the scale bar will be represented. • Select the map units used. There are four possible choices: Map Units is the automated unit selection; Meters, Feet or Nautical Miles force unit conversions. • The Label field defines the text used to describe the units of the scale bar. • The Map units per bar unit allows you to fix the ratio between a map unit and its representation in the scale bar. • You can define how many Segments will be drawn on the left and on the right side of the scale bar, and how long each segment will be (Size field). Height can also be defined. Display The Display dialog of the scale bar Item Properties tab provide the following functionalities (see fig- ure_composer_scalebar_4): Figure 19.22: Scale Bar Display You can define how the scale bar will be displayed in its frame. • Box margin : space between text and frame borders • Labels margin : space between text and scale bar drawing • Line width : line widht of the scale bar drawing 19.3. Composer Items 643 QGIS User Guide, Release 2.6 • Join style : Corners at the end of scalebar in style Bevel, Rounded or Square (only available for Scale bar style Single Box & Double Box) • Cap style : End of all lines in style Square, Round or Flat (only available for Scale bar style Line Ticks Up, Down and Middle) • Alignment : Puts text on the left, middle or right side of the frame (works only for Scale bar style Numeric) Fonts and colors The Fonts and colors dialog of the scale bar Item Properties tab provide the following functionalities (see fig- ure_composer_scalebar_5): Figure 19.23: Scale Bar Fonts and colors Dialogs You can define the fonts and colors used for the scale bar. • Use the [Font] button to set the font • Font color: set the font color • Fill color: set the first fill color • Secondary fill color: set the second fill color • Stroke color: set the color of the lines of the Scale Bare Fill colors are only used for scale box styles Single Box and Double Box. To select a color you can use the list option using the dropdown arrow to open a simple color selection option or the more advanced color selection option, that is started when you click in the colored box in the dialog. 19.3.6 The Basic Shape Items To add a basic shape (ellipse, rectangle, triangle), click the Add basic shape icon or the Add Arrow icon, place the element holding down the left mouse. Customize the appearance in the Item Properties tab. When you also hold down the Shift key while placing the basic shape you can create a perfect square, circle or triangle. The Shape item properties tab allows you to select if you want to draw an ellipse, rectangle or triangle inside the given frame. You can set the style of the shape using the advanced symbol style dialog with which you can define its outline and fill color, fill pattern, use markers etcetera. For the rectangle shape, you can set the value of the corner radius to round of the corners. Note: Unlike other items, you can not style the frame or the background color of the frame. 644 Chapter 19. Print Composer QGIS User Guide, Release 2.6 Figure 19.24: Shape Item properties Tab 19.3.7 The Arrow item To add an arrow, click the Add Arrow icon, place the element holding down the left mouse button and drag a line to draw the arrow on the Print Composer canvas and position and customize the appearance in the scale bar Item Properties tab. When you also hold down the Shift key while placing the arrow, it is placed in an angle of exactly 45° . The arrow item can be used to add a line or a simple arrow that can be used, for example, to show the relation between other print composer items. To create a north arrow, the image item should be considered first. QGIS has a set of North arrows in SVG format. Furthermore you can connect an image item with a map so it can rotate automatically with the map (see the_image_item). Figure 19.25: Arrow Item properties Tab Item Properties The Arrow item properties tab allows you to configure an arrow item. The [Line style ...] button can be used to set the line style using the line style symbol editor. In Arrows markers you can select one of three radio buttons. 19.3. Composer Items 645 QGIS User Guide, Release 2.6 • Default : To draw a regular arrow, gives you options to style the arrow head • None : To draw a line without arrow head • SVG Marker : To draw a line with an SVG Start marker and/or End marker For Default Arrow marker you can use following options to style the arrow head. • Arrow outline color : Set the outline color of the arrow head • Arrow fill color : Set the fill color of the arrow head • Arrow outline width : Set the outline width of the arrow head • Arrow head width: Set the size of the arrow head For SVG Marker you can use following options. • Start marker : Choose an SVG image to draw at the beginning of the line • End marker : Choose an SVG image to draw at the end of the line • Arrow head width: Sets the size of Start and/or headmarker SVG images are automatically rotated with the line. The color of the SVG image can not be changed. 19.3.8 The Attribute Table item It is possible to add parts of a vector attribute table to the Print Composer canvas: Click the Add attribute table icon, place the element with the left mouse button on the Print Composer canvas, and position and customize the appearance in the Item Properties tab. The Item properties of an attribute table item tab provides the following functionalities (see fig- ure_composer_table_1): Figure 19.26: Attribute table Item properties Tab Main properties The Main properties dialogs of the attribute table Item Properties tab provide the following functionalities (see figure_composer_table_2): • For Source you can normally select only ‘Layer features’. 646 Chapter 19. Print Composer QGIS User Guide, Release 2.6 Figure 19.27: Attribute table Main properties Dialog • With Layer you can choose from the vector layers loaded in the project. • The button [Refresh table data] can be used to refresh the table when the actual contents of the table has changed. • The button [Attributes...] starts the Select attributes menu, see figure_composer_table_3, that can be used to change the visible contents of the table. After making changes use the [OK] button to apply changes to the table. In the Columns section you can: – Remove an attribute, just select an attribute row by clicking anywhere in a row and press the minus button to remove the selected attribute. – Add a new attribute use the plus button. At the end a new empty row appears and you can select empty cell of the column Attribute. You can select a field attribute from the list or you can select to build a new attribute using a regular expression. – Use the up and down arrows to change the order of the attributes in the table. – Select a cel in the Headings column to change the Heading, just type a new name. – Select a cel in the Alignment column and you can choose between Left, Center or Right alignment. – Select a cel in the Width column and you can change it from Automatic to a width in mm, just type a number. When you want to change it back to Automatic, use the cross. – The [Reset] button can allways be used to restore it to the original attribute settings. In the Sorting section you can: – Add an attribute to sort the table with. Select an attribute and set the sorting order to ‘Ascending’ or ‘Descending’ and press the plus button. A new line is added to the sort order list. – select a row in the list and use the up and down button to change the sort priority on attribute level. – use the minus button to remove an attribute from the sort order list. Feature filtering The Feature filtering dialogs of the attribute table Item Properties tab provide the following functionalities (see figure_composer_table_4): You can: • Define the Maximum rows to be displayed. • Activate Remove duplicate rows from table to show unique records only. • Activate Show only visible features within a map and select the corresponding Composer map to display the attributes of features only visible on selected map. 19.3. Composer Items 647 QGIS User Guide, Release 2.6 Figure 19.28: Attribute table Select attributes Dialog Figure 19.29: Attribute table Feature filtering Dialog 648 Chapter 19. Print Composer QGIS User Guide, Release 2.6 • Activate Show only features intersecting Atlas feature is only available when Generate an atlas is activated. When activated it will show a table with only the features shown on the map of that particular page of the atlas. • Activate Filter with and provide a filter by typing in the input line or insert a regular expressing use the given expression button. A few examples of filtering statements you can use when you have loaded the airports layer from the Sample dataset: – ELEV > 500 – NAME = ’ANIAK’ – NAME NOT LIKE ’AN% – regexp_match( attribute( $currentfeature, ’USE’ ) , ’[i]’) The last regular expression will include only the arpoirts that have a letter ‘i’ in the attribute field ‘USE’. Appearance The Appearance dialogs of the attribute table Item Properties tab provide the following functionalities (see fig- ure_composer_table_5): Figure 19.30: Attribute table appearance Dialog • With Cell margins you can define the margin around text in each cell of the table. • With Display header you can select from a list one of ‘On first frame’, ‘On all frames’ default option, or ‘No header’. • The option Empty table controls what will be displayed when the result selection is empty. – Draw headers only, will only draw the header except if you have choosen ‘No header’ for Display header. – Hide entire table, will only draw the background of the table. You can activate Don’t draw background if frame is empty in Frames to completely hide the table. – Draw empty cells, will fill the attribute table with empty cells, this option can also be used to provide additional empty cells when you have a result to show! – Show set message, will draw the header and adds a cell spanning all columns and display a message like ‘No result’ that can be provided in the option Message to display • The option Message to display is only activated when you have selected Show set message for Empty table. The message provided will be shown in the table in the first row, when the result is an empty table. • With Background color you can set the background color of the table. Show grid The Show grid dialog of the attribute table Item Properties tab provide the following functionalities (see fig- ure_composer_table_6): 19.3. Composer Items 649 QGIS User Guide, Release 2.6 Figure 19.31: Attribute table Show grid Dialog • Activate Show grid when you want to display the grid, the outlines of the table cells. • With Stroke width you can set the thickness of the lines used in the grid. • The Color of the grid can be set using the color selection dialog. Fonts and text styling The Fonts and text styling dialog of the attribute table Item Properties tab provide the following functionalities (see figure_composer_table_7): Figure 19.32: Attribute table Fonts and text styling Dialog • You can define Font and Color for Table heading and Table contents. • For Table heading you can additionally set the Alignment and choose from Follow column align- ment, Left, Center or Right. The column alignment is set using the Select Attributes dialog (see Fig- ure_composer_table_3). Frames The Frames dialog of the attribute table Item Properties tab provide the following functionalities (see fig- ure_composer_table_8): Figure 19.33: Attribute table Frames Dialog 650 Chapter 19. Print Composer QGIS User Guide, Release 2.6 • With Resize mode you can select how to render the attribute table contents: – Use existing frames displays the result in the first frame and added frames only. – Extent to next page will create as many frames (and corresponding pages) as necessary to display the full selection of attribute table. Each frame can be moved around on the layout. If you resize a frame, the resulting table will be divided up between the other frames. The last frame will be trimmed to fit the table. – Repeat until finished will also create as many frames as the Extend to next page option, except all frames will have the same size. • Use the [Add Frame] button to add another frame with the same size as selected frame. The result of the table that will not fit in the first frame will continue in the next frame when you use the Resize mode Use existing frames. • Activate Don’t export page if frame is empty prevents the page to be exported when the table frame has no contents. This means all other composer items, maps, scalebars, legends etc. will not be visible in the result. • Activate Don’t draw background if frame is empty prevents the background to be drawn when the table frame has no contents. 19.3.9 The HTML frame item It is possible to add a frame that displays the contents of a website or even create and style your own HTML page and display it! Click the Add HTML frame icon, place the element by dragging a rectangle holding down the left mouse but- ton on the Print Composer canvas and position and customize the appearance in the Item Properties tab (see figure_composer_html_1). Figure 19.34: HTML frame, the item properties Tab HTML Source As an HTML source, you can either set a URL and activate the URL radiobutton or enter the HTML source directly in the textbox provided and activate the Source radiobutton. The HTML Source dialog of the HTML frame Item Properties tab provides the following functionalities (see figure_composer_html_2): 19.3. Composer Items 651 QGIS User Guide, Release 2.6 Figure 19.35: HTML frame, the HTML Source properties • In URL you can enter the URL of a webpage you copied from your internet browser or select an HTML file using the browse button . There is also the option to use the Data defined override button, to provide an URL from the contents of an attribute field of a table or using a regular expression. • In Source you can enter text in the textbox with some HTML tags or provide a full HTML page. • The [insert an expression] button can be used to insert an expression like [%Year($now)%] in the Source textbox to display the current year. This button is only activated when radiobutton Source is selected. After inserting the expression click somewhere in the textbox before refreshing the HTML frame, otherwise you will lose the expression. • Activate Evaluate QGIS expressions in HTML code to see the result of the expression you have included, otherwise you will see the expression instead. • Use the [Refresh HTML] button to refresh the HTML frame(s) to see the result of changes. Frames The Frames dialog of the HTML frame Item Properties tab provides the following functionalities (see fig- ure_composer_html_3): Figure 19.36: HTML frame, the Frames properties • With Resize mode you can select how to render the HTML contents: – Use existing frames displays the result in the first frame and added frames only. – Extent to next page will create as many frames (and corresponding pages) as necessary to render the height of the web page. Each frame can be moved around on the layout. If you resize a frame, the webpage will be divided up between the other frames. The last frame will be trimmed to fit the web page. – Repeat on every page will repeat the upper left of the web page on every page in frames of the same size. – Repeat until finished will also create as many frames as the Extend to next page option, except all frames will have the same size. 652 Chapter 19. Print Composer QGIS User Guide, Release 2.6 • Use the [Add Frame] button to add another frame with the same size as selected frame. If the HTML page that will not fit in the first frame it will continue in the next frame when you use Resize mode or Use existing frames. • Activate Don’t export page if frame is empty prevents the map layout from being exported when the frame has no HTML contents. This means all other composer items, maps, scalebars, legends etc. will not be visible in the result. • Activate Don’t draw background if frame is empty prevents the HTML frame being drawn if the frame is empty. Use smart page breaks and User style sheet The Use smart page breaks dialog and Use style sheet dialog of the HTML frame Item Properties tab provides the following functionalities (see figure_composer_html_4): Figure 19.37: HTML frame, Use smart page breaks and User stylesheet properties • Activate Use smart page breaks to prevent the html frame contents from breaking mid-way a line of text so it continues nice and smooth in the next frame. • Set the Maximum distance allowed when calculating where to place page breaks in the html. This distance is the maximum amount of empty space allowed at the bottom of a frame after calculating the optimum break location. Setting a larger value will result in better choice of page break location, but more wasted space at the bottom of frames. This is only used when Use smart page breaks is activated. • Activate User stylesheet to apply HTML styles that often is provided in cascading style sheets. An example of style code is provide below to set the color of

header tag to green and set the font and fontsize of text included in paragraph tags

. h1 {color: #00ff00; } p {font-family: "Times New Roman", Times, serif; font-size: 20px; } • Use the [Update HTML] button to see the result of the stylesheet settings. 19.4 Manage items 19.4.1 Size and position Each item inside the Composer can be moved/resized to create a perfect layout. For both operations the first step is to activate the Select/Move item tool and to click on the item; you can then move it using the mouse while holding the left button. If you need to constrain the movements to the horizontal or the vertical axis, just hold the Shift 19.4. Manage items 653 QGIS User Guide, Release 2.6 while moving the mouse. If you need a better precision, you can move a selected item using the Arrow keys on the keyboard; if the movement is too slow, you can speed up it by holding Shift. A selected item will show squares on its boundaries; moving one of them with the mouse, will resize the item in the corresponding direction. While resizing, holding Shift will maintain the aspect ratio. Holding Alt will resize from the item center. The correct position for an item can be obtained using snapping to grid or smart guides. Guides are set by clicking and dragging in the rulers. Guide are moved by clicking in the ruler, level with the guide and dragging to a new place. To delete a guide move it off the canvas. If you need to disable the snap on the fly just hold Ctrl while moving the mouse. You can choose multiple items with the Select/Move item button. Just hold the Shift button and click on all the items you need. You can then resize/move this group just like a single item. Once you have found the correct position for an item, you can lock it by using the items on the toolbar or ticking the box next to the item in the Items tab. Locked items are not selectable on the canvas. Locked items can be unlocked by selecting the item in the Items tab and unchecking the tickbox or you can use the icons on the toolbar. To unselect an item, just click on it holding the Shift button. Inside the Edit menu, you can find actions to select all the items, to clear all selections or to invert the current selection. 19.4.2 Alignment Raising or lowering functionalities for elements are inside the Raise selected items pull-down menu. Choose an element on the Print Composer canvas and select the matching functionality to raise or lower the selected element compared to the other elements (see table_composer_1). This order is shown in the Items tab. You can also raise or lower objects in the Items tab by clicking and dragging an object’s label in this list. There are several alignment functionalities available within the Align selected items pull-down menu (see ta- ble_composer_1). To use an alignment functionality, you first select some elements and then click on the matching alignment icon. All selected elements will then be aligned within to their common bounding box. When moving items on the Composer canvas, alignment helper lines appear when borders, centers or corners are aligned. 19.4.3 Copy/Cut and Paste items The print composer includes actions to use the common Copy/Cut/Paste functionality for the items in the layout. As usual first you need to select the items using one of the options seen above; at this point the actions can be found in the Edit menu. When using the Paste action, the elements will be pasted according to the current mouse position. Note: HTML items can not be copied in this way. As a workaround, use the [Add Frame] button in the Item Properties tab. 19.5 Revert and Restore tools During the layout process, it is possible to revert and restore changes. This can be done with the revert and restore tools: • Revert last changes • Restore last changes 654 Chapter 19. Print Composer QGIS User Guide, Release 2.6 Figure 19.38: Alignment helper lines in the Print Composer 19.5. Revert and Restore tools 655 QGIS User Guide, Release 2.6 This can also be done by mouse click within the Command history tab (see figure_composer_29). Figure 19.39: Command history in the Print Composer 19.6 Atlas generation The Print Composer includes generation functions that allow you to create map books in an automated way. The concept is to use a coverage layer, which contains geometries and fields. For each geometry in the coverage layer, a new output will be generated where the content of some canvas maps will be moved to highlight the current geometry. Fields associated with this geometry can be used within text labels. Every page will be generated with each feature. To enable the generation of an atlas and access generation parameters, refer to the Atlas generation tab. This tab contains the following widgets (see Figure_composer_atlas): Figure 19.40: Atlas generation tab • Generate an atlas, which enables or disables the atlas generation. •A Coverage layer combo box that allows you to choose the (vector) layer containing the geometries on which to iterate over. • An optional Hidden coverage layer that, if checked, will hide the coverage layer (but not the other ones) during the generation. • An optional Filter with text area that allows you to specify an expression for filtering features from the coverage layer. If the expression is not empty, only features that evaluate to True will be selected. The button on the right allows you to display the expression builder. • An Output filename expression textbox that is used to generate a filename for each geometry if needed. It is based on expressions. This field is meaningful only for rendering to multiple files. 656 Chapter 19. Print Composer QGIS User Guide, Release 2.6 •A Single file export when possible that allows you to force the generation of a single file if this is possible with the chosen output format (PDF, for instance). If this field is checked, the value of the Output filename expression field is meaningless. • An optional Sort by that, if checked, allows you to sort features of the coverage layer. The associated combo box allows you to choose which column will be used as the sorting key. Sort order (either ascending or descending) is set by a two-state button that displays an up or a down arrow. You can use multiple map items with the atlas generation; each map will be rendered according to the coverage features. To enable atlas generation for a specific map item, you need to check Controlled by Atlas under the item properties of the map item. Once checked, you can set: • An input box Margin around feature that allows you to select the amount of space added around each geometry within the allocated map. Its value is meaningful only when using the auto-scaling mode. •A Fixed scale that allows you to toggle between auto-scale and fixed-scale mode. In fixed-scale mode, the map will only be translated for each geometry to be centered. In auto-scale mode, the map’s extents are computed in such a way that each geometry will appear in its entirety. 19.6.1 Labels In order to adapt labels to the feature the atlas plugin iterates over, you can include expressions. For example, for a city layer with fields CITY_NAME and ZIPCODE, you could insert this: The area of [% upper(CITY_NAME) || ’,’ || ZIPCODE || ’ is ’ format_number($area/1000000,2) %] km2 The information [% upper(CITY_NAME) || ‘,’ || ZIPCODE || ‘ is ‘ format_number($area/1000000,2) %] is an expression used inside the label. That would result in the generated atlas as: The area of PARIS,75001 is 1.94 km2 19.6.2 Data Defined Override Buttons There are several places where you can use a Data Defined Override button to override the selected setting. These options are particularly usefull with Atlas Generation. For the following examples the Regions layer of the QGIS sample dataset is used and selected for Atlas Generation. We also assume the paper format A4 (210X297) is selected in the Composite tab for field Presets. With a Data Defined Override button you can dynamically set the paper orientation. When the height (north- south) of the extents of a region is greater than it’s width (east-west), you rather want to use portrait instead of landscape orientation to optimize the use of paper. In the Composition you can set the field Orientation and select Landscape or Portrait. We want to set the orienta- tion dynamically using an expression depending on the region geometry. press the button of field Orientation, select Edit ... so the Expression string builder dialog opens. Give following expression: CASE WHEN bounds_width($atlasgeometry) > bounds_height($atlasgeometry) THEN ’Landscape’ ELSE ’Portrait’ END Now the paper orients itself automatically for each Region you need to reposition the location of the composer item as well. For the map item you can use the button of field Width to set it dynamically using following expression: (CASE WHEN bounds_width($atlasgeometry) > bounds_height($atlasgeometry) THEN 297 ELSE 210 END) - 20 Use the button of field Heigth to provide following expression: (CASE WHEN bounds_width($atlasgeometry) > bounds_height($atlasgeometry) THEN 210 ELSE 297 END) - 20 19.6. Atlas generation 657 QGIS User Guide, Release 2.6 When you want to give a title above map in the center of the page, insert a label item above the map. First use the item properties of the label item to set the horizontal alignment to Center. Next activate from Reference point the upper middle checkbox. You can provide following expression for field X: (CASE WHEN bounds_width($atlasgeometry) > bounds_height($atlasgeometry) THEN 297 ELSE 210 END) / 2 For all other composer items you can set the position in a similar way so they are correctly positioned when page is automatically rotated in portrait or landscape. Information provided is derived from the excellent blog (in english and portugese) on the Data Defined Override options Multiple_format_map_series_using_QGIS_2.6. This is just one example of how you can use Data Defined Overrides. 19.6.3 Preview Once the atlas settings have been configured and map items selected, you can create a preview of all the pages by clicking on Atlas → Preview Atlas and using the arrows, in the same menu, to navigate through all the features. 19.6.4 Generation The atlas generation can be done in different ways. For example, with Atlas → Print Atlas, you can directly print it. You can also create a PDF using Atlas → Export Atlas as PDF: The user will be asked for a directory for saving all the generated PDF files (except if the Single file export when possible has been selected). If you need to print just a page of the atlas, simply start the preview function, select the page you need and click on Composer → Print (or create a PDF). 19.7 Creating Output Figure_composer_output shows the Print Composer with an example print layout, including each type of map item described in the sections above. The Print Composer allows you to create several output formats, and it is possible to define the resolution (print quality) and paper size: • The Print icon allows you to print the layout to a connected printer or a PostScript file, depending on installed printer drivers. • The Export as image icon exports the Composer canvas in several image formats, such as PNG, BPM, TIF, JPG,... • Export as PDF saves the defined Print Composer canvas directly as a PDF. • The Export as SVG icon saves the Print Composer canvas as an SVG (Scalable Vector Graphic). If you need to export your layout as a georeferenced image (i.e., to load back inside QGIS), you need to enable this feature under the Composition tab. Check World file on and choose the map item to use. With this option, the ‘Export as image’ action will also create a world file. Note: • Currently, the SVG output is very basic. This is not a QGIS problem, but a problem with the underlying Qt library. This will hopefully be sorted out in future versions. • Exporting big rasters can sometimes fail, even if there seems to be enough memory. This is also a problem with the underlying Qt management of rasters. 658 Chapter 19. Print Composer QGIS User Guide, Release 2.6 Figure 19.41: Print Composer with map view, legend, image, scale bar, coordinates, text and HTML frame added 19.8 Manage the Composer With the Save as template and Add items from template icons, you can save the current state of a Print Composer session as a .qpt template and load the template again in another session. The Composer Manager button in the QGIS toolbar and in Composer → Composer Manager allows you to add a new Composer template, create a new composition based on a previously saved template or to manage already existing templates. By default, the Composer manager searches for user templates in ~/.qgis2/composer_template. The New Composer and Duplicate Composer buttons in the QGIS toolbar and in Composer → New Composer and Composer → Duplicate Composer allow you to open a new Composer dialog, or to duplicate an existing composition from a previously created one. Finally, you can save your print composition with the Save Project button. This is the same feature as in the QGIS main window. All changes will be saved in a QGIS project file. . 19.8. Manage the Composer 659 QGIS User Guide, Release 2.6 Figure 19.42: The Print Composer Manager 660 Chapter 19. Print Composer CHAPTER 20 Plugins . 20.1 QGIS Plugins QGIS has been designed with a plugin architecture. This allows many new features and functions to be easily added to the application. Many of the features in QGIS are actually implemented as plugins. You can manage your plugins in the plugin dialog which can be opened with Plugins > Manage and install pluginsi .... When a plugin needs to be updated, and if plugins settings have been set up accordingly, QGIS main interface could display a blue link in the status bar to tell you that there are some plugins updating waiting to be applied. 20.1.1 The Plugins Dialog The menus in the Plugins dialog allow the user to install, uninstall and upgrade plugins in different ways. Each plugin have some metadatas displayed in the right panel: • information if the plugin is experimental • description • rating vote(s) (you can vote for your prefered plugin!) • tags • some useful links as the home page, tracker and code repository • author(s) • version available You can use the filter to find a specific plugin. All Here, all the available plugins are listed, including both core and external plugins. Use [Upgrade all] to look for new versions of the plugins. Furthermore, you can use [Install plugin], if a plugin is listed but not installed, and [Uninstall plugin] as well as [Reinstall plugin], if a plugin is installed. If a plugin is installed, it can be de/activated using the checkbox. Installed In this menu, you can find only the installed plugins. The external plugins can be uninstalled and reinstalled using the [Uninstall plugin] and [Reinstall plugin] buttons. You can [Upgrade all] here as well. Not installed 661 QGIS User Guide, Release 2.6 Figure 20.1: The All menu Figure 20.2: The Installed menu 662 Chapter 20. Plugins QGIS User Guide, Release 2.6 This menu lists all plugins available that are not installed. You can use the [Install plugin] button to implement a plugin into QGIS. Figure 20.3: The Not installed menu Upgradeable If you activated Show also experimental plugins in the Settings menu, you can use this menu to look for more recent plugin versions. This can be done with the [Upgrade plugin] or [Upgrade all] buttons. Settings In this menu, you can use the following options: • Check for updates on startup. Whenever a new plugin or a plugin update is available, QGIS will inform you ‘every time QGIS starts’, ‘once a day’, ‘every 3 days’, ‘every week’, ‘every 2 weeks’ or ‘every month’. • Show also experimental plugins. QGIS will show you plugins in early stages of development, which are generally unsuitable for production use. • Show also deprecated plugins. These plugins are deprecated and generally unsuitable for production use. To add external author repositories, click [Add...] in the Plugin repositories section. If you do not want one or more of the added repositories, they can be disabled via the [Edit...] button, or completely removed with the [Delete] button. The Search function is available in nearly every menu (except Settings). Here, you can look for specific plugins. Tip: Core and external plugins QGIS plugins are implemented either as Core Plugins or External Plugins. Core Plugins are maintained by the QGIS Development Team and are automatically part of every QGIS distribution. They are written in one of two languages: C++ or Python. External Plugins are currently all written in Python. They are stored in external repositories and are maintained by the individual authors. 20.1. QGIS Plugins 663 QGIS User Guide, Release 2.6 Figure 20.4: The Upgradeable menu Figure 20.5: The Settings menu 664 Chapter 20. Plugins QGIS User Guide, Release 2.6 Detailed documentation about the usage, minimum QGIS version, home page, authors, and other important in- formation are provided for the ‘Official’ QGIS Repository at http://plugins.qgis.org/plugins/. For other external repositories, documentation might be available with the external plugins themselves. In general, it is not included in this manual. . 20.2 Using QGIS Core Plugins Icon Plugin Description Manual Reference Coordinate Capture Capture mouse coordinate in different CRS Coordinate Capture Plugin DB Manager Manage your databases within QGIS DB Manager Plugin DXF2Shape Converter Converts from DXF to SHP file format Dxf2Shp Converter Plugin eVis Event Visualization Tool eVis Plugin fTools A suite of vector tools fTools Plugin GPS Tools Tools for loading and importing GPS data GPS Plugin GRASS GRASS functionality GRASS GIS Integration GDAL Tools GDAL raster functionality GDAL Tools Plugin Georeferencer GDAL Georeference rasters with GDAL Georeferencer Plugin Heatmap Create heatmap rasters from input vector points Heatmap Plugin Interpolation plugin Interpolation on base of vertices of a vector layer Interpolation Plugin Offline Editing Offline editing and synchronizing with database Offline Editing Plugin Oracle Spatial Georaster Access Oracle Spatial GeoRasters Oracle Spatial GeoRaster Plugin Plugin Manager Manage core and external plugins The Plugins Dialog Raster Terrain Analysis Compute geomorphological features from DEMs Raster Terrain Analysis Plugin Road Graph plugin Shortest path analysis Road Graph Plugin SQL Anywhere plugin Access SQL anywhere DB SQL Anywhere Plugin Spatial Query Spatial queries on vectors Spatial Query Plugin SPIT Shapefile to PostgreSQL/PostGIS Import Tool SPIT Plugin Zonal Statistics Calculate raster statistics for vector polygons Zonal Statistics Plugin MetaSearch Interact with metadata catalogue services (CSW) MetaSearch Catalogue Client . 20.3 Coordinate Capture Plugin The coordinate capture plugin is easy to use and provides the ability to display coordinates on the map canvas for two selected coordinate reference systems (CRS). 1. Start QGIS, select Project Properties from the Settings (KDE, Windows) or File (Gnome, OSX) menu and click on the Projection tab. As an alternative, you can also click on the CRS status icon in the lower right-hand corner of the status bar. 20.2. Using QGIS Core Plugins 665 QGIS User Guide, Release 2.6 Figure 20.6: Coordinate Capture Plugin 2. Click on the Enable on the fly projection checkbox and select a projected coordinate system of your choice (see also Working with Projections). 3. Activate the coordinate capture plugin in the Plugin Manager (see The Plugins Dialog) and ensure that the dialog is visible by going to View → Panels and ensuring that Coordinate Capture is enabled. The coordinate capture dialog appears as shown in Figure figure_coordinate_capture_1. Alternatively, you can also go to Vector → Coordinate Capture and see if Coordinate Capture is enabled. 4. Click on the Click to the select the CRS to use for coordinate display icon and select a different CRS from the one you selected above. 5. To start capturing coordinates, click on [Start capture]. You can now click anywhere on the map canvas and the plugin will show the coordinates for both of your selected CRS. 6. To enable mouse coordinate tracking, click the mouse tracking icon. 7. You can also copy selected coordinates to the clipboard. . 20.4 DB Manager Plugin The DB Manager Plugin is officially part of the QGIS core and is intended to replace the SPIT Plugin and, additionally, to integrate all other database formats supported by QGIS in one user interface. The DB Manager Plugin provides several features. You can drag layers from the QGIS Browser into the DB Manager, and it will import your layer into your spatial database. You can drag and drop tables between spatial databases and they will get imported. You can also use the DB Manager to execute SQL queries against your spatial database and then view the spatial output for queries by adding the results to QGIS as a query layer. The Database menu allows you to connect to an existing database, to start the SQL window and to exit the DB Manager Plugin. Once you are connected to an existing database, the menus Schema and Table additionally appear. The Schema menu includes tools to create and delete (empty) schemas and, if topology is available (e.g., PostGIS 2), to start a TopoViewer. The Table menu allows you to create and edit tables and to delete tables and views. It is also possible to empty tables and to move tables from one schema to another. As further functionality, you can perform a VACUUM and then an ANALYZE for each selected table. Plain VACUUM simply reclaims space and makes it available for reuse. ANALYZE updates statistics to determine the most efficient way to execute a query. Finally, you can import layers/files, if they are loaded in QGIS or exist in the file system. And you can export database tables to shape with the Export File feature. The Tree window lists all existing databases supported by QGIS. With a double-click, you can connect to the database. With the right mouse button, you can rename and delete existing schemas and tables. Tables can also be added to the QGIS canvas with the context menu. If connected to a database, the main window of the DB Manager offers three tabs. The Info tab provides informa- tion about the table and its geometry, as well as about existing fields, constraints and indexes. It also allows you 666 Chapter 20. Plugins QGIS User Guide, Release 2.6 Figure 20.7: DB Manager dialog to run Vacuum Analyze and to create a spatial index on a selected table, if not already done. The Table tab shows all attributes, and the Preview tab renders the geometries as preview. . 20.5 Dxf2Shp Converter Plugin The dxf2shape converter plugin can be used to convert vector data from DXF to shapefile format. It requires the following parameters to be specified before running: Figure 20.8: Dxf2Shape Converter Plugin • Input DXF file: Enter the path to the DXF file to be converted. • Output Shp file: Enter desired name of the shapefile to be created. • Output file type: Specify the geometry type of the output shapefile. Currently supported types are polyline, polygon, and point. 20.5. Dxf2Shp Converter Plugin 667 QGIS User Guide, Release 2.6 • Export text labels: When this checkbox is enabled, an additional shapefile point layer will be created, and the associated DBF table will contain information about the “TEXT” fields found in the DXF file, and the text strings themselves. 20.5.1 Using the Plugin 1. Start QGIS, load the Dxf2Shape plugin in the Plugin Manager (see The Plugins Dialog) and click on the Dxf2Shape Converter icon, which appears in the QGIS toolbar menu. The Dxf2Shape plugin dialog appears, as shown in Figure_dxf2shape_1. 2. Enter the input DXF file, a name for the output shapefile and the shapefile type. 3. Enable the Export text labels checkbox if you want to create an extra point layer with labels. 4. Click [OK]. . 20.6 eVis Plugin (This section is derived from Horning, N., K. Koy, P. Ersts. 2009. eVis (v1.1.0) User’s Guide. American Museum of Natural History, Center for Biodiversity and Conservation. Available from http://biodiversityinformatics.amnh.org/, and released under the GNU FDL.) The Biodiversity Informatics Facility at the American Museum of Natural History’s (AMNH) Center for Biodi- versity and Conservation (CBC) has developed the Event Visualization Tool (eVis), another software tool to add to the suite of conservation monitoring and decision support tools for guiding protected area and landscape plan- ning. This plugin enables users to easily link geocoded (i.e., referenced with latitude and longitude or X and Y coordinates) photographs, and other supporting documents, to vector data in QGIS. eVis is now automatically installed and enabled in new versions of QGIS, and as with all plugins, it can be disabled and enabled using the Plugin Manager (see The Plugins Dialog). The eVis plugin is made up of three modules: the ‘Database Connection tool’, ‘Event ID tool’, and the ‘Event Browser’. These work together to allow viewing of geocoded photographs and other documents that are linked to features stored in vector files, databases, or spreadsheets. 20.6.1 Event Browser The Event Browser module provides the functionality to display geocoded photographs that are linked to vector features displayed in the QGIS map window. Point data, for example, can be from a vector file that can be input using QGIS or it can be from the result of a database query. The vector feature must have attribute information associated with it to describe the location and name of the file containing the photograph and, optionally, the compass direction the camera was pointed when the image was acquired. Your vector layer must be loaded into QGIS before running the Event Browser. Launch the Event Browser module To launch the Event Browser module, click on Database → eVis → eVis Event Browser. This will open the Generic Event Browser window. The Event Browser window has three tabs displayed at the top of the window. The Display tab is used to view the photograph and its associated attribute data. The Options tab provides a number of settings that can be adjusted to control the behavior of the eVis plugin. Lastly, the Configure External Applications tab is used to maintain a table of file extensions and their associated application to allow eVis to display documents other than images. 668 Chapter 20. Plugins QGIS User Guide, Release 2.6 Understanding the Display window To see the Display window, click on the Display tab in the Event Browser window. The Display window is used to view geocoded photographs and their associated attribute data. Figure 20.9: The eVis display window 1. Display window: A window where the photograph will appear. 2. Zoom in button: Zoom in to see more detail. If the entire image cannot be displayed in the display window, scroll bars will appear on the left and bottom sides of the window to allow you to pan around the image. 3. Zoom out button: Zoom out to see more area. 4. Zoom to full extent button: Displays the full extent of the photograph. 5. Attribute information window: All of the attribute information for the point associated with the photo- graph being viewed is displayed here. If the file type being referenced in the displayed record is not an image but is of a file type defined in the Configure External Applications tab, then when you double-click on the value of the field containing the path to the file, the application to open the file will be launched to view or hear the contents of the file. If the file extension is recognized, the attribute data will be displayed in green. 6. Navigation buttons: Use the Previous and Next buttons to load the previous or next feature when more than one feature is selected. Understanding the Options window 1. File path: A drop-down list to specify the attribute field that contains the directory path or URL for the photographs or other documents being displayed. If the location is a relative path, then the checkbox must 20.6. eVis Plugin 669 QGIS User Guide, Release 2.6 Figure 20.10: The eVis Options window 670 Chapter 20. Plugins QGIS User Guide, Release 2.6 be clicked. The base path for a relative path can be entered in the Base Path text box below. Information about the different options for specifying the file location are noted in the section Specifying the location and name of a photograph below. 2. Compass bearing: A drop-down list to specify the attribute field that contains the compass bearing asso- ciated with the photograph being displayed. If compass bearing information is available, it is necessary to click the checkbox below the drop-down menu title. 3. Compass offset: Compass offsets can be used to compensate for declination (to adjust bearings collected using magnetic bearings to true north bearings). Click the Manual radio button to enter the offset in the text box or click the From Attribute radio button to select the attribute field containing the offsets. For both of these options, east declinations should be entered using positive values, and west declinations should use negative values. 4. Directory base path: The base path onto which the relative path defined in Figure_eVis_2 (A) will be appended. 5. Replace path: If this checkbox is checked, only the file name from A will be appended to the base path. 6. Apply rule to all documents: If checked, the same path rules that are defined for photographs will be used for non-image documents such as movies, text documents, and sound files. If not checked, the path rules will only apply to photographs, and other documents will ignore the base path parameter. 7. Remember settings: If the checkbox is checked, the values for the associated parameters will be saved for the next session when the window is closed or when the [Save] button below is pressed.