[GRASS-user] r.sun and r.horizon

[Hamish]

Jonathan Greenberg wrote:
> > I was wondering if there are any conclusions on how best to use
> > r.horizon and r.sun together so they most closely mimic using
> > the -s shadow flag, specifically with daily integrations.

so if you use pre-calc'ed r.horizon maps you should not use the -s flag?


> > We're about to start doing some MASSIVE r.sun processing (input
> > DEM ~ 80gb)

how many cells? have you done trials with a subset of the data?
home much computer & time do you have to throw at the problem?


Markus:
> # step=0.05: 3 minutes time step alias 1deg sun movement
> # horizonstep=1 to match step

(fwiw I simplified a bit: actually 4 minute timestep is 1 deg (4*15=60),
but 3 min is a nice round step= so I used that as "better than 1deg")


> Some notes (and multi-core parallelization trick) have been
> collected at http://grass.osgeo.org/wiki/R.sun
> but a new section of "Recommendations" should be added
> there.

see also trac #498 linked from the above wiki page.


> Contributions welcome.

(this is a big of a group learning exercise)


Hamish