[GRASSLIST:4790] Re: r.sunmask

Hamish hamish_nospam at yahoo.com
Thu Nov 11 17:31:40 EST 2004


> could anybody tell me why r.sunmask is so slow?

limitation of the algorithm I think.


> Do I have to consider something special to use it
> (apart from what is written in the reference manual, I mean).
> Or are there any alternatives?

yes!


> Any hint would be great!

Use r.sun to create the shade map; see the "Shadow maps" hint in the
help page:

http://grass.ibiblio.org/grass57/manuals/html57_user/r.sun.html


It isn't as exact[*], but I think the difference is minor.


[*] "The solar geometry of the model is based on the works of Krcho
(1990), later improved by Jenco (1992). The equations describing Sun
- Earth position as well as an interaction of the solar radiation
with atmosphere were originally based on the formulas suggested by
Kitler and Mikler (1986). This component was considerably updated by the
results and suggestions of the working group co-ordinated by Scharmer
and Greif (2000) (this algorithm might be replaced by SOLPOS
algorithm-library included in GRASS within r.sunmask command)."


Hamish




More information about the grass-user mailing list