[GRASS-user] cost surface

Colin Nielsen colin.nielsen at gmail.com
Thu Mar 26 10:06:33 EDT 2009

Hi Ricardo,
It is hard to tell what is going from without looking at your input
file, but you do seem to using r.cost correctly. My guess would be
that the differences between cells are not great enough to cause the
cost surface to deviate from a linear trajectory. To test this, try
using r.mapcalc to amplify the pattern on the r_vias surface, ie.
"r_vias_x100=r_vias*100" (100 might be too much), then re-run r.cost
with the r_vias_x100 as the input.

r.cost does take a relatively long time to run, especially on surfaces
which are relatively smooth (I think that's true). The result should
be relatively identical to arc's cost weighted function.


On Wed, Mar 25, 2009 at 10:59 AM, Ricardo Almendra
<ricardoalmendra85 at gmail.com> wrote:
> Hello
> I'm trying to built a cost surface. I've already built a raster with the
> pixel cost,  but i can´t get the cost that is required to arrive to point A.
> I'm trying - "r.cost input=r_vias at 12_03 output=exp start_rast=h_rast at 12_03
> max_cost=0 percent_memory=100" but it takes a lot of time and the result
> it's linear, it do not  reflect the differences in the original raster.
> I' trying to do something similar to the cost weighted function in arcgis.
> Tks
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