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.
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 installation manager. Get the latest information on binary packages at the QGIS website at http://download.qgis.org.
If you need to build QGIS from source, please refer to the installation instructions. They are distributed 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
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.
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 downloaded 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:
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://qgis.org/downloads/data/ and unzip the archive on your system.
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/.
Starting QGIS is done as you usually do for any other application on your platform. It means that you can launch QGIS by:
To stop QGIS, click:
In previous section you learned how to start QGIS. You will see that QGIS also provides further 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 [--noversioncheck] don't check for new version of QGIS at startup [--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 [--authdbdirectory path] use the given directory for authentication database [--code path] run the given python file on load [--defaultui] start by resetting user ui settings to default [--dxf-export filename.dxf] emit dxf output of loaded datasets to given file [--dxf-extent xmin,ymin,xmax,ymax] set extent to export to dxf [--dxf-symbology-mode none|symbollayer|feature] symbology mode for dxf output [--dxf-scale-denom scale] scale for dxf output [--dxf-encoding encoding] encoding to use for dxf output [--dxf-preset visiblity-preset] layer visibility preset to use for dxf output [--help] this text [--] treat all following arguments as FILEs 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
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, qgis --lang it starts QGIS in Italian localization.
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:
Command line option --nologo
This command line argument hides the splash screen when you start QGIS.
command line option --noversioncheck
Don’t check for new version of QGIS at startup.
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:
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 --authdbdirectory
Again, this option is similar to the one above but define the path to the directory where the authentication database will be stored.
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
Command line options --dxf-*
These options can be used to export QGIS project into a DXF file. Several options are available:
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:
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.
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.... If the loaded project file on disk was meanwhile changed, by default, QGIS will ask you if you want to overwrite the changes into the project file. This behavior is set by checking Prompt to save project and data source changes when required under Settings ‣ Options ‣ General menu .
At startup, a list of screenshot with the name and path of each of the most recent projects (up to ten) is shown instead of a white and empty map canvas. This is a handy and quicker way to remember what a project was about and double-click a row opens the selected project. If you’re willing to create a new project, just add new layers and the list disappears.
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:
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 any more. To be made aware of this, in the General tab under Settings ‣ Options you should tick Warn when opening a project file saved with an older version of QGIS.
Whenever you save a project in QGIS a backup of the project file is made with the extension .qgs~.
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: