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

[MacQueen, Don]

Thank you!
-Don

--
Don MacQueen
Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062


From: jctorres <jctorres at ugr.es<mailto:jctorres at ugr.es>>
Date: Saturday, March 22, 2014 12:04 AM
To: "MacQueen, Don" <macqueen1 at llnl.gov<mailto:macqueen1 at llnl.gov>>, "grass-user at lists.osgeo.org<mailto:grass-user at lists.osgeo.org>" <grass-user at lists.osgeo.org<mailto:grass-user at lists.osgeo.org>>
Subject: Re: [GRASS-user] Elevation differences between endpoints of least cost paths

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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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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