GIS

GIS on Linux with SAGA

Joey Bernard — Fri, 12 Jul 2019 12:00:00 +0000

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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Gabor Farkas' Practical GIS (Packt Publishing)

James Gray — Fri, 26 May 2017 16:15:56 +0000

by James Gray

Open-source GIS tools are maturing rapidly, and Gábor Farkas' new book Practical GIS is a guide to applying these tools to managing geographic information like a pro at minimal cost. Farkas deploys the popular QGIS application and explains how to use it to generate useful spatial data. From there, readers are guided through the basics of queries, data management and geoprocessing.

After mastering the essentials, readers practice their knowledge on real-world examples, solving various types of geospatial analyses with appropriate methods.

Finally, readers learn how to publish data (and results) on the web with QGIS Server and GeoServer and create a basic web map with the API of the lightweight Leaflet web-mapping library. Storing data in a PostGIS database also is treated in the book.

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Mapping Your GIS Data

Joey Bernard — Wed, 09 Oct 2013 20:36:36 +0000

by Joey Bernard

I've already looked at some GIS applications available on Linux. Programs like GRASS and qgis provide a full set of tools to do GIS. Sometimes, that's really overkill though. You may just want to display some data geographically and create a map. For those cases, there is Thuban, an interactive geographic data viewer.

Most distributions should have a package available within their package management systems. If not, you always can download the sources and build it from scratch. It does depend on Python, among several other libraries, so you need to do a bit of a dependency dance. Binary downloads even are available for Windows and Mac OS X, so you can point your non-Linux friends to them.

If you don't already have data of your own, sources of public-domain GIS data are available on-line. Here are a couple: http://www.naturalearthdata.com/features and http://wiki.openstreetmap.org/wiki/Shapefiles. The files available on these sites will get you started with SHP files that contain at least basic features for most of the world.

Thuban is not as flexible as full-fledged GIS software and cannot handle very many data file formats. You can use SHP files, DBF database files and various image file formats. In the screenshots for this article, I simply grabbed several of the data files available on-line.

When you start Thuban, you end up with a completely blank slate (Figure 1). The first step is to start a new session, which you can do by selecting the menu item File→New Session (not much will change on the screen). In order to start building your map, you need to add layers that can be manipulated. I started by selecting the menu item Map→Add Layer and adding in an SHP file to give me the basic geographic attributes for my home province of New Brunswick (Figure 2). This includes several different geographical items, such as water, river banks and parks. The default display is not very interesting yet (Figure 3).

Figure 1. Starting Thuban gives you a blank slate.

Figure 2. Adding a new layer opens a file selection dialog where you can choose an SHP file.

Figure 3. By default, Thuban just displays all of the data with a single symbol color.

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