[GRASS-dev] v.surf.bspline with sparse_input - get interpolated values in attribute table

Paulo van Breugel p.vanbreugel at gmail.com
Sun May 14 11:04:51 PDT 2017

On 14-05-17 17:04, Markus Neteler wrote:
> Hi
> On May 13, 2017 10:42 PM, "Paulo van Breugel" <p.vanbreugel at gmail.com 
> <mailto:p.vanbreugel at gmail.com>> wrote:
> >
> > Hi, when using v.surf.bspline with sparse vector map points 
> (sparse_input) the output vector map is a 3D vector point map with the 
> interpolated values as z-values. However, I want to get the 
> interpolated values as values in a column of the attribute table. Any 
> idea how to do this?
> You can use v.to.db for this task:
> https://grass.osgeo.org/grass72/manuals/v.to.db.html#examples

Thanks. It takes a few more steps because the output vector layer of 
v.surf.bspline has only one category, so v.to.db with option=coor will 
not work. What I am doing now is:

v.surf.bspline input=calibration sparse_input=validationpoints \
     column=elevation output=bspline_1
v.category input=bspline_1 output=bspline_2 option=del cat=-1
v.category input=bspline_2 output=bspline_3 option=add
v.db.addtable map=bspline_3
v.db.addcolumn map=bspline_3 \
     columns='x double precision,y double precision,z double precision'
v.to.db map=bspline_3 option=coor columns=x,y,z

which feels like a lot of steps to accomplish this. Is there a better 
way to do this?

> Markus

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