Thank you! -Don -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062
From: jctorres <[email protected]<mailto:[email protected]>> Date: Saturday, March 22, 2014 12:04 AM To: "MacQueen, Don" <[email protected]<mailto:[email protected]>>, "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> 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 -- ======================================================================= Juan Carlos Torres | http://lsi.ugr.es/~jctorres<http://lsi.ugr.es/%7Ejctorres> Laboratorio de Realidad Virtual | Tlf.: (+34) 645 885 167 Dpto. Lenguajes y Sistemas Informaticos | (+34) 958 249 307 ETS. Ing. Informatica | interno ugr 71 260 Univ. de Granada | FAX: (+34) 958 243 179 ======================================================================= 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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