[GRASS-user] Elevation differences between endpoints of least cost paths

[jctorres]

Hi Don

I think you can solve this using grass 7 (you can download it from 
http://grass.osgeo.org/download/software/). This version includes a new 
option for r.cost that copies the value of the nearest cell. You can 
solve the problem using

r.mapcalc "streamH=if(isnull(stream.thin),null(),FD)"

r.cost -k input=area.one output=dtv start_rast=streamH nearest=nearestH

nearestH will contains the elevation of the nearest stream

Best regards


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Juan Carlos Torres                      | http://lsi.ugr.es/~jctorres
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El 21/03/14 23:47, MacQueen, Don escribió:
> I'm stating with a DEM (named FD).
>
> First I find streams:
>    r.watershed elevation=FD stream=stream
>    r.thin input=stream output=stream.thin
>
> Then, for each point on the DEM, I need
>   The distance to the nearest point in a stream
>   The elevation difference to the stream point
>
> I can get the distance by gollowing the example "Computing a distance map"
> in Neteler & Mitasova's GRASS book:
>    r.mapcalc area.one=1
>    r.cost -k input=area.one output=dtv start_rast=stream.thin
>
> So far so good, and the results make sense
>
> But I would very much appreciate suggestions for the elevation difference.
>
> I have been looking at various r.* routines, such as r.drain, but haven't
> yet found a solution. I have very little experience with raster analysis.
> (and in fact, I'm using the R package spgrass6 to manage the above steps)
>
> Thanks
> -Don
>
>

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