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 -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/i-atcorr-negative-DEM-tp6374760p6375046.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
