[GRASS-user] real distance analysis

[Hamish]

Bödõcs wrote:
> I would like to examine from an exact point that territory, which is
> inside an determinated distance from the exact point. BUT I don't want
> to use the map projected distance (=Buffer zone), but the datas of a
> DEM.
> 
> I would like to measure the "really" surface, the climbing etc. For
> example I need the maximum distance "cirlce"  (30km or 30 mph doeas
> not matter) around a point, but measured in the "filed"(=DEM) not on
> the map (=projected area).

Andrew wrote:
> If I'm not mistaken, you mean the distance as it would be measured on
> the ground, rather than in plan.  In mountainous areas, 1km in plan is
> a lot different from 1km on the ground.  I've wondered how to approach
> this as well, and would like to hear what others think.

GRASS 6.1:
 r.walk

GRASS 6.0 or by hand:
 r.cost + "r.mapcalc distance=costmap*map_resolution"

http://grass.ibiblio.org/grass61/manuals/html61_user/r.cost.html
http://grass.ibiblio.org/grass61/manuals/html61_user/r.walk.html


It works well.


IIRC, the leics GRASS tutorial had an example using r.cost. (GRASS 4.2)
http://www.geog.le.ac.uk/assist/grass/seeds/
?


Hamish