[GRASS-user] r.sun with shadowing effects

Hi all,

I need to calculate the solar radiation (with r.sun) of a relatively small area taking into account the shadowing effect of reliefs spread in a much larger area. In order to be able to get a high resolution map of the area of interest, or even just the values relatives to some particular sites, is there a way to avoid the long computational time needed for areas I’m not interested in?
May be I can use r.los for selecting the reliefs that actually cast a shadow on the area of interest?

Thanks in advance for your answer.

Odoardo Zecca


Dott. Odoardo Zecca
Institut Agricole Régional
Regione La Rochère 1/A
11100 Aosta
email: o.zecca@iaraosta.it
Tel. +39 0165 215884
Fax +39 0165 215800

Odoardo Zecca wrote:

I need to calculate the solar radiation (with r.sun) of a relatively small
area taking into account the shadowing effect of reliefs spread in a much
larger area. In order to be able to get a high resolution map of the area of
interest, or even just the values relatives to some particular sites, is
there a way to avoid the long computational time needed for areas I'm not
interested in?

I don't think so (at least not without modifying the code), but I would be
interested in the same functionality.

May be I can use r.los for selecting the reliefs that actually cast a shadow
on the area of interest?

That would be ok for the beam radiation, but you might affect the diffuse and
reflective radiation calculations that way. ?

Hamish

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HamishB wrote:

Odoardo Zecca wrote:

I need to calculate the solar radiation (with r.sun) of a relatively
small
area taking into account the shadowing effect of reliefs spread in a much
larger area. In order to be able to get a high resolution map of the area
of
interest, or even just the values relatives to some particular sites, is
there a way to avoid the long computational time needed for areas I'm not
interested in?

I don't think so (at least not without modifying the code), but I would be
interested in the same functionality.

There is some hope: from JRC I received an unpublished r.sun2 + r.horizon
which separates (the slow) horizont calculation from the (much faster)
energy
calculations. Run r.horizon once and then r.sun2 as often as you need.

I'll check if I can put it into GRASS Addons SVN.

Markus
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Thank you, Hamish and Markus.
I look forward downloading the new r.sun2 and r.horizon!

Odoardo

On Wed, Oct 10, 2007 at 01:17:37PM +0200, Odoardo Zecca wrote:

   Thank you, Hamish and Markus.
   I look forward downloading the new r.sun2 and r.horizon!

   Odoardo

The new r.sun2 and r.horizon are now available in the
GRASS SVN Addons repository. The documentation still needs
to be updated (see TODO file therein).

Markus

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ITC -> dall'1 marzo 2007 Fondazione Bruno Kessler
ITC -> since 1 March 2007 Fondazione Bruno Kessler
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