[Routing] Routing on Garmin etrex using OSM

[Robert Vollmert]

Hello,

sorry for messing up the threading: I just ran across the thread in  
the archives.

 >> we only know the bitmap-format for the map-images. The graph- 
format used for the routing-data is completely unknown.
 >... but has been reverse engineered by someone in Poland (I believe)  
who sells his software "cgpsmapper" which, in the professional  
version, can produce routable maps, and it could be used to make  
routable OSM maps. I think we've not done it thus far because we  
always hoped to find a free solution...
there's been some effort to reverse engineer the format of the routing  
data. Both in libgarmin.sourceforge.net and mkgmap (see http://svn.parabola.me.uk/display/trunk/) 
. In particular, the NOD files (at least those created by cgpsmapper)  
are mostly understood. These contain the routing network.
Unfortunately, it appears that part of the extended header of TRE also  
affects routing. That's still a mystery. But if you have some time,  
give it a try! Reverse engineering can be quite addictive.
Cheers
Robert