Elena Mezzini wrote: > > > Markus Metz-2 wrote: >> >> On Tue, May 17, 2011 at 10:08 PM, Elena Mezzini >> <[email protected]> wrote: >>> >>> On Tue, May 17, 2011 at 9:22 PM, Elena Mezzini >>> <[email protected]> wrote: >>>> Hi all, >>>> I'm once again in trouble with i.atcorr in GRASS6.5.svn. >>>> I notice that my output reflectance images are strange: there are some >>>> areas >>>> that are really bright and other that are really dark. Both seem to >>>> match >>>> with my DEM raster. >>>> Could there be problems with negative values in DEM?? I'm in a coastal >>>> area >>>> and there are some real altitude negative values. >>> >>> i.atcorr (the 6S code it is using to be exact) should treat negative >>> elevation values as elevation = 0. It is debatable if this is correct, >>> but in theory i.atcorr should behave accordingly. Actually, I am not >>> sure about it's behaviour for negative elevation values... >>> >>> You could set all negative elevation values to zero, >>> >>> >>> Ok, how can I do it? >>> >> replace my_elevation with the name of your elevation map: >> >> g.region rast=my_elevation >> r.mapcalc "elevation_positive = if(my_elevation < 0, 0, <my_elevation>)" >> >> >> >> g.region rast=dem_sross_srtm >> r.mapcalc "dem_sross_srtm_pos = if(dem_sross_srtm < 0, 0, >> <dem_sross_srtm>)" >> >> Syntax error! >> As you know I'm not a programmer... where is the error? >> >> Thank you once again >> >> Elena >> > > Found: > > g.region rast=dem_sross_srtm > r.mapcalc "dem_sross_srtm_pos = if(dem_sross_srtm < 0, 0, dem_sross_srtm)" > > Sorry! > > Elena >
No differences between negative and positive values... I don't know what could be the problem... Thank you for your helpfulness! Elena -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/i-atcorr-negative-DEM-tp6374760p6375143.html Sent from the Grass - Users mailing list archive at Nabble.com. _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
