[GRASSLIST:4526] Re: roads cut slopes in right angle

[Eric G. Miller]

On Wed, Sep 18, 2002 at 09:20:45AM +0300, orkun wrote:
> Hi
> 
> Does anyone have an idea about how to query a road map to get a new map 
> in which roads cut slopes in right angle ?

Hmmm, maybe:

Convert vector roads to raster at resolution << than road width.
Create a raster elevation layer just along these road centerlines:
  r.mapcalc 'elev_roads = if (!isnull(centerline), elevation)'
Now, grow the elev_roads to the width of the road (r.resample?) --
not sure if that will work well.
Finally:

r.mapcalc 'cut_elev = if (!isnull(elev_roads2), elev_roads, elevation)'

Don't know if that'll work too well because the r.resample is liable
just create a NULL raster -- not sure how it's handling the NULL's in
the input.

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