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I'm new to GRASS gis and I'm trying to do a topographic correction (i.topo.corr) of 9 ASTER bands using SRTM dem. I keep getting this error message:
ERROR: Illumination model is of CELL type
Is this error referring to my elevation raster, and if so how do I change the type to the appropriate one?
"CELL" type means integer type (see also http://grasswiki.osgeo.org/wiki/GRASS_raster_semantics#Raster_map_precision_types). Since SRTM is delivered as integer map but i.topo.corr expects a floating point map, you need to convert/resample that map beforehand.
For resampling methods available in GRASS GIS, see the manual or Wiki, especially:
http://grasswiki.osgeo.org/wiki/Interpolation#Resampling_of_raster_maps_to_finer_resolution
since you may want to match the resolution of your DEM to that of the ASTER channels.
