Falk Grossmann wrote: > Dear Grass users, > > My objective is to calculate the length of a line (GPS tracklog) in a > very mountainous terrain. In this case I will need to take into > account the 3D aspect. Can't you import the tracklog as 3D line with v.in.ogr -z? The imported vector may contain both points and lines. Then v.to.db option=length?
> I see two ways of working this: > > 1) Converting the points to line vector and than using a DEM to > calculate the length. In ESRI software I would convert the DEM rasta > to a TIN and than overlay the line vector to calculate length. > However, as DEM's in Africa are course (and in the process of weaning > myself of ESRI) I would imagine I would be better of using something > along the lines described bellow in GRASS: > > 2) Use of the converted point to line vector and than incorporate the > point vector (GPS tracklog) which contains x,y,z data points to > calculate the "3D" element which needs to be added to the length. > Maybe I need to segment the line, than "extract" the slope of the line > segments (from on GPS point to the next) and than use the map > calculator to get the length of each segment? > > I wondering if there are any tools in GRASS which deal with this in > one go (maybe in the hydro tools or terrain?) For method 2 I am > wondering how can calculate the slop of a line - since the attributes > are attached the the start and stop GPS points of that segment. > > Any suggestions much appreciated, > > Thanks > > Falk > > > > > > > ------------------------------------------------------------------------ > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user > _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
