Fwd: Re: [GRASS-dev] VTK export for lat-long locations

[Hamish]

Sören Gebbert wrote:
> I dont think this is a good idea. It is a nice and easy approach
> indeed, but IMHO the length of the z height does not depend on 
> the length of a line on the surface. 
> So the z elevation is independend from the positon
> on the surface (i know the earth is not a perfect sphere ... ;) ), 
> in this case the row number.


the units of z are map dependent and not knowable by the system.

for NVIZ + lat/lon, in the past I have used r.mapcalc to make a new
map, [I've got a feeling this is no longer needed??]

e.g. for a lat/lon map with z in meters:

r.mapcalc "scaled_map = (map / 1850.0*60)"

so x,y,z are all in degrees.


I would not bother with reprojecting lat/lon into square cells, the user
can to that with r.proj if they want. Just note that the output is in
Plate Carrée like GRASS renders for 2D.

see also 'r.shaded.relief units='.


Hamish