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@osgeo.org>
> >
> > wrote:
> >> Dylan,
> >>
> >> On Tue, Jan 6, 2009 at 10:01 PM, Dylan Beaudette
> >>
> >> <debeaudette@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@unipg.it
ivan.marchesini@gmail.com
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