[GRASSLIST:2399] Re: The g3.region settings ....

[Geotronix]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

* giovedì 29 gennaio 2004, alle 10:44, Markus Neteler scrive:
> On Wed, Jan 28, 2004 at 01:40:06PM +0100, Geotronix wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> > 
> > Hi,
> > 
> > I'm trying to get s.vol.rst to work for the computation of rainfall map
> > using a 50m resolution cell (1000x1000 cells grid).
> > Now, the site file that's input for s.vol.rst has 4 columns
> > x|y|z|%rainfall(mm/year)
> > 
> > When I tried to launch s.vol.rst the first time it told me that I had to
> > set the 3D region. SO I launched g3.createregion which reead the
> > defaults from the current 2D region. I gave him the following options:
> > 
> > g3.createregion t=2500 b=0 dres=1
> > 
> > as to resemble:
> > 
> > t=2500 --> max altitude in meters that I have on my dem;
> > b=0  --> min altitude on my dem ;
> > dres=1 -->vertical resolution on 1 meter.
> 
> It's probably much better, if you eventually just want to extract a 2D
> rainfall map, to run the computation in a single-layer volume:
> 
> g3.createwind t=2500 b=0 dres=2500
> 
>  t=2500 --> max altitude in meters that I have on my dem;
>  b=0  --> min altitude on my dem ;
>  dres=2500 -->vertical resolution 2500 meter.
> 
> Then s.vol.rst ...
> 
> Please report if this is faster.
> 
>  Markus Neteler

You're right! It's a lot faster.... but what does it change pratically
form using a dres=2500 instead of dres=1? IS the result diffrent?

There a re a few things that are not stated in the docs of s.vol.rst and
r.surf.rst.
What unit measure are used when I state smooth=1; tension=50 and
zmult=50. Are these percent values. If I don't know what units I'm
dealing with,how can I state some sort of mathimatical relation between
the values of these parameters and the geological/meteorological problem
I'm dealing with.
Let me make an example. Of my 25 stations, most of them have low
variance of the mean while a few have a very high variance. This lets me
think that I could use the smooth parameter set to zero for all the low
variance rainfall stations while I should use a higher smoothing for
the stations that have I higher variance. Is this conceptually correct?
But how do I relate the variance to the smoothing parameter?

Thanks
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.2 (GNU/Linux)

iD8DBQFAGTnyIRaQQEznKxURAnDLAJ9D/vlZeevqHc6F5bpvoIWXcnbvAQCfcf+h
yrOeoxQliLNsz46xFRA7520=
=8c/e
-----END PGP SIGNATURE-----