Blog Entries tagged gis
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Playing with a SkyTraq Venus GPS logger under Linux

Published: 2009-07-28 21:40 UTC. Tags: linux gis

I got a new toy today - a GPS logger. Got it as part of a magazine subscription deal - two issues + GPS logger for about $12. That magazine was not my kind of magazine, but getting a GPS logger delivered home for $12 was worth having to throw away two magazine issues :-). For other people trying to get this to work under Linux, the magazine in question was Aktiv Träning.

After some fiddling, I came to the conclusion that the device is based on the SkyTraq Venus chipset:

skytraq: Venus device found: Kernel version = 1.3.3, ODM version = 1.4.5, revision (Y/M/D) = 07/12/11

After plugging the device into an USB port, it appears as a serial port, in my case /dev/ttyUSB0. The data can be retrieved using GPSBabel, but it has to be the development version - the stable version does not feature the skytraq driver required. The development version is available via CVS from sourceforge, see http://sourceforge.net/projects/gpsbabel/develop for details on how to access CVS.

Once you have the development version of gpsbabel, getting the data is as easy as:

./gpsbabel -D 9 -i skytraq,initbaud=38400,baud=38400,erase -f /dev/ttyUSB0 -o gpx -F out.gpx

This will write the GPS coordinate log to out.gpx in the GPS Exchange format - a lightweight XML format.

The above command will also erase the log from the device, so the next download contains just the latest log.

Since I like playing with Google Earth, I also learned that the GPX can be converted into KML - the format Google Earth can read, by running:

./gpsbabel -i gpx -f out.gpx -o kml -F out.kml

Just open out.kml with Google Earth, and you'll see where the GPS logger has been.

On popular request, here's a few images of the device.

Skytraq Venus device Inside the battery compartment of a Skytraq Venus device

The label inside the battery compartment has the following text:

GT-750F/L-Lite
GPS Receiver(Data Logger)
RoHS CE FCC ID:VHP-750F
Made in Taiwan CANMORE
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Calculating the Distance of a GPS log

Published: 2009-07-28 21:20 UTC. Tags: linux gis

Playing with my GPS logger, I wanted to know the distance travelled between all the points in a GPS log. For example, if I went for a bicycle trip and brought the logger, it would be nice to know how many kilometers I have travelled.

Trying to find a tool that did this without being cumbersome to use proved more difficult than I thought, so I did a quick hack with the help of the python bindings for gpsd. It's a very simple script:

$ ./distance.py promenad2.gpx
427.077378454

Given a GPX file, it will print out the number of meters travelled.

Fetch it in the fgpstools repository on github

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