[GRASS-user] v.vol.rst problem

[ivan marchesini]

Dear grass users..
I'm working with grass6 devel.
Trying to use v.vol.rst with option "cellout" I have obtained a strange
result:

The "elev" 3D map is correctly created (I have seen it by means of nviz)
but the cellout map is created as a small map (like a miniature of the
map that I would expect) that is placed at the up-left corner of the
region.. (I'm using monitors and I haven't MASK in my mapset). The
remaining part of the cellout map has only values = 0.

I think I can obtain the same thing using r3.cross.rast starting from
the "elev" map created from v.vol.rst, but: could the problem I have
found be a little bug? or it is a problem o f zmult or wmult (but the
resolution is the same along the x,y,z directions...) 

thanks...

Ivan




Il giorno ven, 09/01/2009 alle 12.41 -0800, Dylan Beaudette ha scritto:
> On Wednesday 07 January 2009, Helena Mitasova wrote:
> > On Jan 7, 2009, at 11:19 AM, Dylan Beaudette wrote:
> > > On Tue, Jan 6, 2009 at 2:33 PM, Markus Neteler <neteler at osgeo.org>
> > >
> > > wrote:
> > >> Dylan,
> > >>
> > >> On Tue, Jan 6, 2009 at 10:01 PM, Dylan Beaudette
> > >>
> > >> <debeaudette at ucdavis.edu> wrote:
> > >>> Hi,
> > >>>
> > >>> For some crazy reason I was under the impression that it is
> > >>> possible to do
> > >>> interpolation with a covariate with v.vol.rst. Are there any
> > >>> examples on how
> > >>> to parameterize this module, when a 2D surface is requested,
> > >>> rather than a 3D
> > >>> volume. I noticed the 'cellinp' argument for a cross-section, but
> > >>> this is not
> > >>> quite what I am after. I am looking to do something very similar to
> > >>> interpolation of rainfall data, taking into account the
> > >>> orographic effect of
> > >>> terrain.
> > >>
> > >> This was my main business (say, of our cluster) over the last
> > >> months :)
> > >> You can do that. I am using the elevation model as auxiliary
> > >> variable:
> > >>
> > >> # something like this:
> > >> v.vol.rst in=vectpoints cellinp=dem wcolumn=pointval cellout=rst2d
> > >>
> > >> cellout delivers the 2D map, extracted from the volume along the
> > >> dem map.
> > >>
> > >> Hope this helps
> > >> Markus
> > >
> > > Thanks Markus. One more question: have you found a good compromise in
> > > the 3D region settings- i.e. some ratio of horizontal:vertical
> > > resolution that gives good results and doesn't take too long to
> > > compute?
> >
> > you need to set your vertical resolution based on the spatial
> > variability you want to capture
> > and then don't forget to use appropriate zmult that will stretch the
> > vertical distances so that
> > they are about the same magnitude as horizontal distances (e.g. if
> > your horizontal res. is 10m
> > and vertical is 0.1m you need zmult around 100, if you want
> > anisotropic effects it may be less -
> > see more on how to find the parameters here:
> > http://skagit.meas.ncsu.edu/~helena/gmslab/papers/
> > TGIS2002_Hofierka_et_al.pdf
> >
> > I hope this helps, Helena
> >
> > > Cheers,
> > >
> > > Dylan
> 
> Thanks for the tips Helena. I'll check on that paper, and report back with the 
> results.
> 
> Dylan
> 
-- 
Ti prego di cercare di non inviarmi files .dwg, .doc, .xls, .ppt.
Preferisco formati liberi.
Please try to avoid to send me .dwg, .doc, .xls, .ppt files.
I prefer free formats.
http://it.wikipedia.org/wiki/Formato_aperto
http://en.wikipedia.org/wiki/Open_format

Ivan Marchesini
Department of Civil and Environmental Engineering
University of Perugia
Via G. Duranti 93/a 
06125
Perugia (Italy)
Socio fondatore GFOSS "Geospatial Free and Open Source Software" http://www.gfoss.it
e-mail: marchesini at unipg.it
        ivan.marchesini at gmail.com
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