Create, display, and evaluate geodata with QGIS

Map Game

Article from Issue 213/2018
Author(s):

Create and display geospatial data with the versatile and popular QGIS.

Most modern mapping information is not stored as a single complete picture, the way it used to be when you found your geographic information from a map on a wall or in an atlas. Maps have become fully integrated with the digital revolution. The map you view from your computer screen or telephone is transmitted to the device as a bundle of geospatial information that is stored in a file or database. An application on the receiving device assembles this data into a view that the user can recognize as a map.

This geospatial data is available online from many sources, including research institutions, government agencies, and nonprofit groups. Of course, it is also possible to create your own geographical information file, which is the modern equivalent of drawing your own map. Another option is somewhere between the alternatives of downloading or rolling your own: Many users start with public information and then customize the map by adding their own annotations and features.

Linux supports numerous Geographical Information System (GIS) tools that help to create, edit, analyze, and visualize geospacial data. One of the most popular GIS solutions is QGIS [1]. The Quantum-GIS geographical tool, which has undergone continuous development since 2002, is licensed under GPLv2 and available for several platforms.

QGIS uses a PostgreSQL database with the PostGIS extension to capture geographical elements. The modular structure of the software allows the user to extend the functionality by adding plugins. QGIS also supports interfaces to OpenStreetMap, GRASS GIS, and various statistics programs. The system can handle all common vector and raster graphics formats.

With its simple user guidance and sophisticated display functions, QGIS has established itself as an important tool for research professionals. Excellent multilingual documentation and tutorials mean that the software is also quite accessible to beginners.

Installation

You will find precompiled QGIS packages in the repositories of all major Linux distributions; however, if you want to be sure you have the most recent version, manual setup is a better option. The project website provides detailed documentation on integrating QGIS into various systems [2]. Be sure to read the notes on supported operating system versions, because not all program versions work with all Linux distributions due to missing dependencies. For some Debian derivatives, you must first install the apt-transport-https package, because the QGIS repositories work with SSL encryption.

To start QGIS, click QGIS Desktop in the Start menu. First, a configuration window lets you decide whether to transfer data from a previous version. After you click on one of the options, the program window opens. The window appears largely empty for new installations without imported data (Figure 1). The main window is divided into five sections: At the top, you will find an extensive menubar and a buttonbar. On the left, a browser and a layer area appear below each other, and on the right you will see a list of recently edited projects.

Figure 1: The left panel of the main window hints at the wealth of possibilities offered by QGIS.

If you load one of your projects, the map view appears in the right window area. The browser and layer areas display the map elements in a tree view. The browser displays data carriers, linked geodatabases, and map services; the layers represent the different levels of a map. The software visualizes the layers hierarchically, so that moving or (de-)activating the individual layers changes the map image accordingly. A status bar at the bottom of the window provides information on coordinates, scale, and magnification of the map.

Individual

The flexible interface can easily adapt to your ideas. For example, minimizing the layer and browser view creates more space for the map. You can place individual window segments anywhere by dragging the titlebar while holding down the left mouse button. To switch the window segments completely on and off, use the dialog panels in the View menu.

The toolbar consists of individual tool groups that you can move individually to the margins of the program window and arrange vertically. If necessary, switch complete tool groups on or off via View | Toolboxes.

To remove individual unneeded buttons from the toolbars, open the Settings | Interface Customizations… menu and check the Enable customizations option in the overlaying window. You can then navigate through the individual menu hierarchies and deactivate unnecessary options by unchecking the boxes (Figure 2). To apply the changes, restart the software.

Figure 2: Activate or deactivate the control elements in the Interface Customization dialog box.

For friends of shortcuts, QGIS offers the option of defining individual shortcuts for different functions in the Settings | Shortcuts menu. In the Settings | Options dialog, you can also adjust the font and icon size to your requirements. This function is particularly useful for very high-resolution screens, since the default size for icons and fonts on screens beyond FHD resolutions (1920x1080 pixels) often appear too small.

Mess of Data

Many public institutions provide data on a variety of topics for free download over the web. Other geographical data is available in the form of Web Map Service files (WMS) on the servers of public institutions.

QGIS lets you load this free geographical data into a new or existing project. In the menubar in the Layer | Add Layer menu, you will find various options for creating a new map layer. Depending on the data format, you have to differentiate between vector and raster data. You can also integrate a database into the software, and you can then localize and load the data in a small file manager on the local mass storage system. The software supports several common database formats.

The downloaded data appears on the left in the layer area.

You can complete this task more elegantly in the browser area, which also contains a small file manager. From the browser area, you can transfer the data using drag-and-drop. If several geo files are in the directory, right-click on the desired file and select Add Selected Layer(s) to Map (Figure 3).

Figure 3: Maps consist of several independent layers, which QGIS lists on the lower-left corner.

Buy this article as PDF

Express-Checkout as PDF
Price $2.95
(incl. VAT)

Buy Linux Magazine

SINGLE ISSUES
 
SUBSCRIPTIONS
 
TABLET & SMARTPHONE APPS
Get it on Google Play

US / Canada

Get it on Google Play

UK / Australia

Related content

  • Processing Map Data with OpenLayers

    OpenLayers is a JavaScript library that allows you to integrate maps into web pages. You can program the geodetic data directly or read it from a database.

  • uMap

    uMap provides an easy way to create advanced maps based on the OpenStreetMap service. This article explains how to put uMap's features and functionality to practical use.

  • Web Design with GIMP

    Good homepage design is a question of the layout. Sometimes the best option is to use a graphics program to design the page, then translate the result into HTML code. The versatile image manipulation program GIMP can help.

  • Perl: Photos Effects

    With the GIMP image editing program, and a little help from Perl, you can enhance your digital photos and transform a modern image into a nostalgic turn-of-the-century shot.

  • Moving Art

    Pencil2D, an easy-to-use painting and 2D animation program, lets you create small animations quickly. Despite the simple user interface, you might need a little help getting started.

comments powered by Disqus

Direct Download

Read full article as PDF:

Price $2.95

News