On Tue, May 17, 2011 at 9:22 PM, Elena Mezzini <elena.mezz...@gmail.com> 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? run i.atcorr again and compare the results to the i.atcorr results using the original DEM. If there are any differences that do not make sense, please fill in a bug ticket. Markus M Thank you! Elena -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/i-atcorr-negative-DEM-tp6374760p6374961.html Sent from the Grass - Users mailing list archive at Nabble.com. _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user