Learning QGIS - Second Edition

4.5 (2 reviews total)
By Anita Graser
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About this book

QGIS is a user friendly open source geographic information system (GIS) that runs on Linux, Unix, Mac OSX, and Windows. The popularity of open source geographic information systems and QGIS in particular has been growing rapidly over the last few years. More and more companies and institutions are adopting QGIS and even switching to it their main GIS.

Learning QGIS Second Edition is a practical, hands-on guide updated for QGIS 2.6 that provides you with clear, step-by-step exercises to help you apply your GIS knowledge. Through a number of clear, practical exercises, this book will introduce you to working with QGIS quickly and painlessly. This book takes you from installing and configuring to handling spatial data to creating great maps. You will learn how to load and visualize existing spatial data and create data from scratch. You will perform common geoprocessing and spatial analysis tasks and automate them. We will cover how to achieve great cartographic output and print maps. Finally, you will learn to extend using Python and even create your own plugin.

Publication date:
December 2014
Publisher
Packt
Pages
150
ISBN
9781784392031

 

Chapter 1. Getting Started with QGIS

In this chapter, we will install and configure the QGIS geographic information system. We will also get to know the user interface and how to customize it. By the end of this chapter, you will have QGIS running on your machine and be ready to start with the tutorials.

 

Installing QGIS


QGIS runs on Windows, various Linux distributions, Unix, Mac OS X, and Android. Also, the QGIS project provides ready-to-use packages as well as instructions to build from the source code at http://download.qgis.org. We will cover how to install QGIS on two systems: Windows and Ubuntu, as well as how to avoid the most common pitfalls.

Note

Further installation instructions for other supported operating systems are available at http://www.qgis.org/en/site/forusers/alldownloads.html.

Like many other open source projects, QGIS offers you a choice between a stable release version and the cutting-edge developer version, also called master or testing. QGIS master/testing will contain the latest and greatest developments, but be warned that on some days, it might not work as reliably as you want it to. For the tutorials in this book, we will use the QGIS 2.6 stable release.

Installing QGIS on Windows

On Windows, we have two different options to install QGIS: the standalone installer and the OSGeo4W installer. The standalone installer is one big file to download (approximately 260 MB for the 64-bit version and 320 MB for the 32-bit version); it contains a QGIS release and the Geographic Resources Analysis Support System (GRASS) GIS in one package. The OSGeo4W installer is a small, flexible installation tool that makes it possible to download and install QGIS and many more OSGeo tools with all their dependencies. The main advantage of this over the standalone installer is that it makes updating QGIS and its dependencies very easy. You can always have access to both the current and the developer versions, if you chose to, but of course, you are never forced to update. That is why I recommend that you use OSGeo4W. You can download the 32-bit and 63-bit OSGeo4W installers from http://osgeo4w.osgeo.org (or directly from http://download.osgeo.org/osgeo4w/osgeo4w-setup-x86.exe for the 32-bit version or http://download.osgeo.org/osgeo4w/osgeo4w-setup-x86_64.exe if you have a 64-bit version of Windows). Download the version that matches your operating system and keep it! In the future, whenever you want to change or update your system, just run it again.

Tip

Regardless of the installer you choose, make sure that you avoid special characters such as German umlauts or letters from alphabets other than the default Latin ones in the installation path, as they can cause problems later on, for example, during plugin installation.

When the OSGeo4W installer starts, we get to choose between the Express Desktop, Express Web-GIS, and Advanced installations. To install the QGIS release version, we can simply select the Express Desktop option, and the next dialog box will list the available desktop applications, such as QGIS, uDig, and GRASS GIS. We can simply select QGIS, click on Next, and the download and installation will start automatically. When the installation is finished, there will be desktop shortcuts and start-menu entries for OSGeo4W and QGIS.

If we want to install QGIS master/testing, we need to go through the Advanced installation. This installation path offers many options, such as Download without installing and Install from Local Directory, which can be used to download all the necessary packages on one machine to later install them on machines without Internet access. It's usually not necessary to change the default settings, but if your machine is, for example, hidden behind a proxy, you will be able to specify it here. After the installer fetches the latest package information from OSGeo's servers, we get to pick the packages for installation. QGIS master/testing is listed in the desktop category as qgis-dev. To select it for installation, click on the text that reads Skip, and it will change and display the version number. The installer will automatically select all the necessary dependencies (such as GDAL, SAGA, OTB, and GRASS), so we don't have to worry about this. After clicking on Next, the download and installation starts automatically, just like in the Express version. The dialog will look like the following screenshot:

If you try to run QGIS and get a pop up that says, The procedure entry point <some-name> could not be located in the dynamic link library <dll-name>.dll, it means that you are facing a common issue on Windows systems: a DLL conflict. This error is easy to fix; just copy the DLL file mentioned in the error message from C:\OSGeo4W\bin\ to C:\OSGeo4W\apps\qgis\bin\ (adjust the paths if necessary).

Installing QGIS on Ubuntu

On Ubuntu, the QGIS project provides packages for both the release and developer versions. At the time of writing this book, the Ubuntu versions Precise, Saucy, and Trusty, are supported, but you can find the latest information at http://qgis.org/en/site/forusers/alldownloads.html#ubuntu. Be aware, though, that you can only install one version at a time. The packages are not listed in the default Ubuntu repositories. Therefore, we have to add the appropriate repositories to Ubuntu's source list, which you can find at /etc/apt/sources.list. You can open the file with any text editor.

Make sure that you have superuser rights, as you need them to save your edits. One option is to use gedit, which is installed on Ubuntu by default. To edit the sources.list file, use the following command:

sudo gedit /etc/apt/sources.list

Make sure that you add only one of the following four package-source options to avoid conflicts due to incompatible packages. The specific lines that you have to add to the source list depend on your Ubuntu version.

  1. The first option, which is also the default one, is to install the current version. To install the QGIS release on Trusty Tahr, add the following lines to your file:

    deb     http://qgis.org/debian trusty main
    deb-src http://qgis.org/debian trusty main

    If necessary, replace trusty with saucy or precise to fit your system. For an updated list of supported Ubuntu versions, visit http://download.qgis.org.

  2. The second option is to install the QGIS master, which is currently available for trusty, saucy, utopic, and precise. Add the following lines to your file:

    deb     http://qgis.org/debian-nightly trusty main
    deb-src http://qgis.org/debian-nightly trusty main

    Tip

    The preceding versions depend on other packages such as GDAL and proj4, which are available in the Ubuntu repositories. It is worth mentioning that these packages are often quite old.

  3. The third option is to install the QGIS release version with updated dependencies, which are provided by the ubuntugis repository. Add the following lines to your file:

    deb http://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu trusty main 
    deb-src http://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu trusty main
  4. The fourth option is the QGIS master with updated dependencies. Add the following lines to your file:

    deb     http://qgis.org/ubuntugis-nightly trusty main
    deb-src http://qgis.org/ubuntugis-nightly trusty main
    deb     http://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu trusty main

After choosing the repository, we will add the qgis.org repository's public key to our apt keyring. This will avoid warnings that you might otherwise get when installing from a non-default repository. Run the following command in the terminal:

gpg --keyserver keyserver.ubuntu.com --recv DD45F6C3
gpg --export --armor DD45F6C3 | sudo apt-key add –

Note

By the time this book goes into print, the key information might change. Refer to http://qgis.org/en/site/forusers/alldownloads.html#ubuntu for the latest updates.

Finally, to install QGIS, run the following commands:

sudo apt-get update
sudo apt-get install qgis python-qgis qgis-plugin-grass
 

Running QGIS for the first time


When you install QGIS, you get two applications: QGIS Desktop and QGIS Browser. If you are familiar with ArcGIS, you can think of QGIS Browser as similar to ArcCatalog. It is a small application to preview spatial data and related metadata. For the remainder of this book, we will focus on QGIS Desktop.

By default, QGIS uses the operating system's default language. To follow the tutorials in this book, I advise you to change the language to English by going to Settings | Options | Locale. On the first run, the way the toolbars are arranged can hide some buttons. To be able to work efficiently, I suggest that you rearrange the toolbars. I like to add some toolbars on the left and right screen borders to save vertical screen estate—especially on wide screen displays.

Additionally, we activate the file browser by going to View | Panels | Browser. It provides us with a quick access to our spatial data. In the end, the QGIS window on your screen should look similar to the following screenshot:

Next, we activate some must-have plugins by going to Plugins | Manage and Install Plugins. Plugins are activated by ticking the checkboxes beside their names. To begin with, I recommend the following:

  • Coordinate Capture: This plugin is useful to pick coordinates in the map

  • fTools: This plugin offers vector analysis and management tools

  • GdalTools: This plugin offers raster analysis and management tools

  • Processing: This plugin provides access to many useful raster and vector analyses tools as well as a model builder for task automation

To make it easier to find specific plugins, we can filter the list of plugins using the Search input field at the top of the window, which you can see in the following screenshot:

 

Introducing the QGIS user interface


Now that we have set up QGIS, let's get accustomed to the interface! As we already saw in the screenshot presented in the Running QGIS for the first time section, the biggest area is reserved for the map. To the left of the map, there are the Layers and Browser panels. In the following screenshot, you can see how the Layers panel looks like once we have loaded some layers (which we will do in the upcoming chapter Viewing Spatial Data). To the left of each layer entry, you can see a preview of the layer style. Additionally, we can use layer groups to structure the layer list. The Browser panel (shown in the following screenshot) provides us with a quick access to our spatial data, as you will soon see in the following chapter.

Below the map, we find important information such as (from left to right) the current map Coordinates, map Scale, and the (currently inactive) project coordinate reference system (CRS), for example, EPSG:4326 in the following screenshot:

Next, there are multiple toolbars to explore. If you arrange them as shown in the previous section, the top row will look like this:

The first row contains the following toolbars:

  • File: This toolbar contains the tools to create, open, save, and print projects

  • Manage Layers: This toolbar contains the tools to add layers from the vector or raster files, databases, web services, and text files or create new layers

  • Database: Currently, this toolbar only contains DB Manager, but other database-related tools (for example, the OfflineEditing plugin, which allows us to edit offline and synchronize with databases) will appear here when they are installed

  • Help: Toolbar points to the option to download the user manual

The second row of toolbars looks like this:

The second row contains the following toolbars:

  • Map Navigation: This contains the pan and zoom tools

  • Attributes: These tools are used to identify, select, open attribute tables, measure, and so on

  • Label: These tools are used to add, configure, and modify labels

On the left screen border, we will add the following toolbar:

  • Raster: This toolbar includes histogram stretch, brightness, and contrast control

  • Vector: This currently only contains the Coordinate Capture tool, but it will be filled by additional Python plugins

  • Plugins: This is currently empty, but will be filled by additional Python plugins

  • Web: This is currently empty, but will be filled by additional Python plugins

Finally, on the right screen border, we find the following toolbar:

  • Digitizing: The tools in this toolbar enable editing, basic feature creation, and editing

  • Advanced Digitizing: This toolbar contains the undo/redo option, advanced editing tools, the geometry-simplification tool, and so on

Tip

All digitizing tools are currently inactive. They will only turn active once we start editing a vector layer.

Toolbars and panels can be activated and deactivated via the View menu's Panels and Toolbars entries as well as by right-clicking on a menu or toolbar, which will open a context menu with all the available toolbars and panels. All the tools on the toolbars can also be accessed via the menu. If you deactivate the Manage Layers toolbar, for example, you will still be able to add layers using the Layer menu.

QGIS is highly customizable. You can increase your productivity by assigning shortcuts to the tools you use regularly, by navigating to Settings | Configure shortcuts. Similarly, if you find that you never use a certain toolbar button or menu entry, you can hide it by navigating to Settings | Customization. For example, if you don't have access to an Oracle Spatial database, you might want to hide the associated buttons to remove the clutter and save the screen estate, as shown in the following screenshot:

 

Summary


In this chapter, we installed QGIS and configured it by selecting useful defaults and arranging the user-interface elements. Finally, we explored the panels, toolbars, and menus that make up the QGIS user interface and learned how to customize them to increase productivity. In the following chapter, we will use QGIS to view spatial data from different data sources such as files, databases, and web services.

About the Author

  • Anita Graser

    Anita Graser is a spatial data scientist, open source GIS advocate, and author with a background in geographic information science. She is currently working with the Center for Mobility Systems at the Austrian Institute of Technology in Vienna and teaching QGIS classes at UNIGIS Salzburg. She serves on the QGIS project steering committee. and has published several books about QGIS. Furthermore, she develops tools, such as the Time Manager plugin for QGIS. You can follow her on Twitter @underdarkGIS.

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Latest Reviews

(2 reviews total)
Very helpful resource. Does a great job with the basics of QGIS and I'm happy to have it available.
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