[GRASS-user] gps trajectories

[Bram Van Moorter]

Dear,
The past days I have been trying to find out the best way to represent
different gps trajectories in GRASS with the dates of the locations.
1. I used R to create SpatialLinesDataFrame and exported it in a shape
file for GRASS.
2. I got stuck in GRASS, because I couldn't access the vertices (i.e.
the points) of the different lines (for each individual trajectory one
line). I wanted to access each point to be able to connect it to a
database with the dates, I need these vertices also for subsequent
operations. [is it really not possible to directly access and
manipulate the vertices in a line?]
3. I tried "v.to.points -v" to extract the vertices, worked fine, I
have now an object with two layers: the points and the individuals.
4. I got stuck since this new object is no longer a line, but a
collection of points, fortunately organized in a hierarchical way
(i.e. nested within individuals)...
Possibly as a consequence, I could no longer easily use
d.vect.thematic to plot the trajectories from each individual.

I have been looking on the web for anything useful on how to use GRASS
for the representation of GPS trajectories, in vain (apart from
functions to read from gps receivers, I have simple csv files for the
trajectories).  Therefore, I am curious about the experiences of other
people in this context.  And maybe a few tips could help me further on
my way.
Cheers,
Bram

-- 
Bram Van Moorter
Centre for Conservation Biology
NTNU, Trondheim (Norway)
email:  Bram.Van.Moorter at gmail.com
website: http://ase-research.org/moorter