I'm starting to mess about with the solar radiation packages of GRASS and ArcGIS and have become rather stuck on the GRASS side of matters. I have a DSM area, and that is feeding into GRASS well enough, however when processing on the default values it falls over, not outputting anything. I'm using the command...
g.region rast=elevation.dem r.sun -s elev=elevation.dem day=180 r.colors col=grey d.his i_map=beam_map h_map=elevation.dem
In the R.Sun man page, the following command is recommended:
g.region rast=elevation.dem r.sun -s elev=elevation.dem slop=slope asp=aspect beam=beam_map day=180 r.colors beam_map col=grey d.his i_map=beam_map h_map=elevation.dem
However here, where am I supposed to get the slope, aspect and beam from?