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?


'Beam' is output. 'Slope' and 'Aspect' should be computed from the DEM. For details, follow the link at the bottom of the R.sun man page to the R.Slope.Aspect man page.

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