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 <nete...@osgeo.org> > > > > wrote: > >> Dylan, > >> > >> On Tue, Jan 6, 2009 at 10:01 PM, Dylan Beaudette > >> > >> <debeaude...@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 -- Dylan Beaudette Soil Resource Laboratory http://casoilresource.lawr.ucdavis.edu/ University of California at Davis 530.754.7341 _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user