[GRASS-user] How to export 3D vector elevations with v.out.gpsbabel
needels at translucida.com
Sat Mar 6 19:22:59 EST 2010
The v.out.gpsbabel module is wonderful. I particularly like the way to
automatically reprojects data into Lat/LonWGS84.
I have been importing multiple GPS tracks (of hiking trails) into
GRASS for "averaging", then using v.out.gpsbabel to export a .gpx
track format for use on my GPS. I recently used v.drape to pull
elevations from a DEM into the vector, and had hoped that using
v.out.gpsbabel to export the resulting 3D vector would automatically
export the elevation into the standard "ele" GPX data field.
Unfortunately, the elevations all exported as 0.
Am I missing an option to have v.out.gpsbabel do this automatically?
If not, this would be a nice enhancement.
If not, is there a workaround I can use?
The v.out.gpsbabel manual indicates that an attribute field named
"ele" would be exported as elevation, but I can't quite figure out how
to get the elevation from wherever it is stored in a 3D vector
(associated with vertex geometry?) into an attribute table and from
there into an exported track.
Since the exported track needs an elevation associated with each track
point (rather than line), I created a points vector using v.to.points -
v, added an "ele" column to layer 2 (the layer with cats for the
points), and then used v.what.rast to pull elevation values from a DEM
into the "ele" column.
Unfortunately, when I tried to use v.out.gpsbabel layer=2 -w to export
to waypoints (or -t to export to tracks) it fails with the following
197: [: : integer expression expected
ERROR: Error reading categories: [ -76.28746517 39.40506425
ERROR: Error reprojecting data
By the way, the first line (m.proj: line 197:[: : integer expression
expected) occurs every time I use v.out.gpsbabel, even when it
successfully exports a .gpx file.
Any ideas what is going on here? Other ways to 3D vector elevations
exported into a .gpx track file?
I am running William Kyngesburye's 6.4RC5-3 on Mac OS X Leopard.
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