[GRASS-user] Making and Uploading Maps for Garmin Etrex Legend GPS - v.net.salesman

John C. Tull john.tull at wildnevada.org
Wed Aug 13 13:28:01 EDT 2008

You need to do it as a route, not a track, to avoid the ends  
connecting. I did this last year, and I think it worked as one would  

Here was my process:
1) Generate the vector line.
2) Reduce the number of nodes if your GPS is limited in available  
storage with v.generalize (this can require many iterations and  
tweaking of commands to get it right)
3) Export as a shapefile making sure that it is of type line, as this  
is a segment
4) Convert to epsg:4326 if necessary (ogr2ogr -t_srs epsg:4326 ...)
5) Use ogr2ogr or gpsbabel to make a gpx file (you can also do the  
simplify stuff with gpsbabel simplify rather than v.generalize, if you  
6) Transfer to unit with gpsbabel as a route: gpsbabel -r -i gpx -o  
garmin -f gpxfile -F /dev/yourgpsdevice

I think you can skip 5 and go straight from shapefile to garmin unit,  
but not sure.


On Aug 13, 2008, at 7:22 AM, John Stevenson wrote:

> Thanks to everyone for their help so far.  It seems like this is  
> much less straightforward than I had expected.  I've looked into  
> some of the options e.g. QLandkarte, cGISmapper and tried to upload  
> a ready-made .img file but had problems with the port speed (I'm  
> using a usb/serial converter to connect to the GPS).
> As I am most interested in loading up my road data, I thought about  
> putting them on as tracks.  I exported the vector map to kml, then  
> used gpsbabel to convert to .gpx format.  I then edited this by hand  
> to name the tracks and join all the parts into track segments.   
> Unfortunately when it loads up, all the segments get joined together  
> so that the end of one road jumps onto the start of the next.  I  
> think that either gpsbabel or my etrex don't support that feature.
> So now I have a new plan:  is it possible to use v.net.salesman to  
> export a single track that covers every road in my network and  
> doubles back on itself to return to the start?  If so, can someone  
> give me some pointers on how to do it - I'm still getting to grips  
> with the vector format and don't really have a clue where to start.
> Thanks,
> John

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