GIS on Linux with SAGA


In this article, I want to look at a GIS option available for Linux—specifically, a program called SAGA (System for Automated Geoscientific Analyses). SAGA was developed at the Department of Physical Geography in Germany. It is built with a plugin module architecture, where various functions are provided by individual modules. A very complete API is available to allow users to extend SAGA's functionality with newly written modules. I take a very cursory look at SAGA here and describe a few things you might want to do with it.

Installing SAGA should be as easy as looking at the software repository for your favourite distribution. For Debian-based distros, you can install it with the command:

sudo apt-get install saga

When you first start it, you get a blank workspace where you can begin your project.

Figure 1. SAGA starts up with a central project window, several tool panes on the left and console messages at the bottom.

Two major categories of data sets are available that you can use within your projects: satellite imagery and terrain data. The tutorial website provides detailed walk-throughs that show how you can get access to these types of data sets for use in your own projects. The tutorial website also has sections on some of the processing tools available for doing more detailed analysis.

SAGA understands several data file formats. The typical ones used in GIS, like SHP files or point clouds, are the default options in the file selector window. You can work with these types of data, or satellite imagery or terrain data.

Let's start by looking at terrain analysis in SAGA. You'll need digital elevation data, in DEM format, which is available from the SRTM Tile Grabber site. You will get a zip file for each region you select, and these zip files contain geotiff files for the selected regions.

Load the geotiff file by clicking File→Open. By default, it will show only the common project file formats. To locate your downloaded geotiff files, you'll need to change the filter at the bottom of the file selector window to be all files. Once it is loaded, it will show up in the list of data sources in the bottom-left window pane.

Figure 2. You can load data sources, such as geotiffs, into your project.