[GRASS-user] Rsun problems

Hamish hamish_nospam at yahoo.com
Thu May 31 03:55:57 EDT 2007

Silvia Franceschi wrote:
> I am trying to use r.sun and have some problems understanding the
> results. If I want the total irradiation in a specified day then I
> have to select  the option 2. In this case I obtain the following
> maps: - beam_rad: irradiation raster file
> - insol_time: insolation raster map
> - diff_rad: irradiation raster map
> - refl_rad: irradiation raster map
> So I don't understand a few things... :-(
> - where does GRASS save the irradiation raster file?

it's not one output file, it's a raster map named whatever you gave the
beam_rad option. see below.

> - what is the difference between the diff_rad irradiation raster map
> and the refl_rad irradiation raster map.

one is diffuse light (think cloud scatter), the other reflected light
(glare bouncing off ground hitting hillside??).

> - I noticed that I have a raster map created with the name of the 
> beam_rad "file", so I think in this case GRASS makes a raster and not
> a file, but what do these values means?

yes, beam_rad mades a raster map, not some data file. This is already
changed in the development source code.

mode 2 units are Wh.m-2.day-1.  Watt-hours per meter^2 per day.

> - which of these maps created whit the command gives to me the total 
> radiation for the day? maybe I have to sum some of them but I don't 
> understand which of them to take into account.

total = beam + diffuse + reflected
(add with r.series)


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