[GRASS-user] new addon for multivariate surface interpolation from sparse points with smoothing

[Vaclav Petras]

Hi Markus,

On Thu, Aug 25, 2016 at 3:02 PM, Markus Metz <markus.metz.giswork at gmail.com>
wrote:
>
> The new addon v.surf.tps performs multivariate thin plate spline
> interpolation of sparse points with smoothing.

really interesting. I did some preliminary tests and I might provide some
feedback later. For now I updated the examples in the manual in r69259, so
please update your svn copy.

> If you ever wondered
> why worldclim data (http://worldclim.org) follow so nicely elevation,
> the reason is multivariate thin plate spline interpolation of
> meteorological station data with elevation as a covariate.
> [...] The module works only with GRASS 7.2+.

It may be useful to note that you can preform similar operation with any
version of GRASS GIS using v.vol.rst (3D interpolation using regularized
spline with tension). The trick is using cross_* parameters to extract the
desired 2D raster. Here is an example from [2]:

g.region raster=elev_state_500m -p
g.region t=2000 b=0 tbres=2000 res3=500 -p3
v.vol.rst input=precip_30ynormals_3d \
    cross_input=elev_state_500m cross_output=precip_anntopo_500m \
    maskmap=elev_state_500m wcolumn=annual zscale=90 segmax=700

Thanks!
Vaclav

[1] https://trac.osgeo.org/grass/changeset/69259
[2]
http://ncsu-geoforall-lab.github.io/geospatial-modeling-course/grass/interpolation_2.html
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