The surface and below

GIS is about collecting and processing all kinds of geopgraphic information. Creating maps from this information is just one of the exercises. A lot of very useful information, IMHO the best collection available, can be found on the FreeGIS project pages.

My primary goal is/was to create a map from geo-data I collected with my GPS receiver. This does sound quite primitive, one might think at first sight, but interestingly there is no such free software for Linux available to do so. It is quite frustrating because you get all the data you need from your GPS receiver and have no means at all to postprocess them into something that at least comes close to a map.

So I started out to look for solution that could at least help me on my way. The first packages everyone will step over that starts with GIS is GRASS. GRASS is the most universal geo processing tool that exists, I think. But it is a tool in the old Unix tradition - very powerful but not less complex. So for newbies in GIS like me, GRASS was no option; though I think it would serve my purpose to a certain extend.

Other very interesting projects are e.g. GMT and iGMT, both tools to generate quite nice looking graphic representations from GIS data, not necessarily only maps. The iGMT also links to very interesting topographic data for the whole world! You can generate topo maps for the whole world from this data, very cool!

But those projects/packages do not solve my problem. What I need is a program than can

• import NMEA/GPS data as track (vector or polygon, no just points)
• ability to edit waypoint, i.e. add/delete points, join tracks, break tracks
• annotate tracks, i.e. add attributes like name, type of road, etc.

Concerning those features I finally found three projects that could be promising:

• Quantum GIS - QGIS, a Qt based GIS application that offers plugins for various in- and output options, also GPS import, and some editing functions. It still lacks proper annotation and vextor editing.
• Navsys is intended as a project for finally creating a free navigation system software for Linux. All software is rewritten from scratch using latest GTK+. Nice idea and good start but especially the map editor is still in very early development.
• Thuban is a very promising and professional looking application, very similar to QGIS and also still in heavy development. It also lacks the ability to edit the track data but it already can do proper annotation to a certain degree.

I am currently focusing on Thuban. One reason for that is that I know the Intevation guys quite well ;) The other is that I dislike Qt, sorry folks. Both QGIS and Thuban require so called shape-files as input. This seems to be a quite common format for geo vector data. QGIS has an import plugin for importing GPS data or rather to convert GPS data into shape files.

Frankly speaking this converter did not work for me but it directed me into a new direction, not to look for GIS applications being able to import GPS-NMEA but rather to preprocess this data in something GIS applications do like. After some googling I found an extension to GPSman and the C implementation gpstr2shp.c. This application uses shapelib for shapefile output. But it wants GPSman style tracks as input and since I do not use GPSman (and no expensive Garmin GPS) I quickly hacked up a filter to convert NMEA data into GPS tracks.

And here we are now, we have a shape file from GPS/NMEA data!

A next step could be to write an output module for GPSbabel, a quite powerful GPS data translator. We'll see...