[GRASS-user] interpolating with a covariate - v.vol.rst

[Markus Neteler]

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

PS: If you are interested, I have a patch of v.vol.rst which reduces the
 computational time to roughly 30%. Done by a friend of mine
 (mathematician) who removed unneeded function calls from the code.
 Needs more testing...