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.

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