[GRASS-user] r.sunmask (position) and r.shaded.relief

Hamish hamish_b at yahoo.com
Wed Feb 8 03:01:11 EST 2012

Paolo wrote:
> > What is in short, the difference between the two commands?

Markus N:
> They are completely different.
> r.sunmask calculated the sun position for a given
> date-time, optionally writing out
>   a sun cast shadow map (not shaded!)

note that r.sun output maps can be used to good effect with
the d.shadedmap module to make a "more-correct" version of a
typical r.shaded.relief image.

e.g. http://bambi.otago.ac.nz/hamish/grass/screenshots/deep_cove_rsun.jpg

perhaps only worth it if you already have the r.sun result in

> r.shaded.relief generates a shaded relief from a DEM to be
> used as background for other maps.

(you can place the sun's angle in the sky at whatever angle you
like, but the effect is purely a visual one; r.sunmask uses a
real solar movement algorithm and outputs in shadow/out of
shadow data map)


ps- debian has a site set up where you can upload a screenshot
of any package it hosts. I wonder what it would take to set up
a similar thing for GRASS? so people could easily upload a screen
shot of any particular module in action.
(a javascript/Pylons [python web frameworks] dev volunteer 
would be needed)

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