[GRASS-user] long run time with r.sunmask

[Markus Neteler]

Dylan Beaudette wrote on 03/08/2007 02:25 AM:
> Hi everyone,
>
> using the latest CVS, I noticed that running r.sunmaks on a relatively small 
> region (300x300 cells) took a very long time to run (about 15 minutes). I am 
> using a DEM for the location and specifying the time of day, and day of the 
> year. I used the following command:
>
> r.sunmask elev=elev_meters out=shadows_afternoon timezone=-8 year=2007 month=3 
> day=31 hour=16 minute=00 second=00
>
> Any idea on why this would take so long?
>   
... because of r.sunmask slowliness...
For a fast solution, use r.sun instead.
  Shadow maps
       A  map  of  shadows can be extracted from the solar incidence
angle map (incidout). Areas with
       zero values are shadowed. The -s flag has to be used.

cheers
Markus