[GRASS-user] GRASS 6.4 How to extract point-values from multiple rasters

Tim Michelsen timmichelsen at gmx-topmail.de
Sat Apr 6 04:11:09 PDT 2013

>>> I have to extract isolated value from several raster.
Yesterday I had the same task to solve:
have a vector with some sampling points and wanting to insert values
from 2 raster layers to the table.

>> The GRASS module r.what [0] extracts raster values at a
>> given location. As input you need to give the name of the
>> raster map and the coordinates as east,north
>> [0] http://grass.osgeo.org/grass64/manuals/r.what.html
> note that r.what can take multiple rasters and multiple point-
> values as input, all in one pass, to make a table.
I do not understand why r.what should be of help here.

r.what [1] just prints out.
Isn't the right tool v.sample [2]?
But this tool works in a way the user would not expect it:

Now, the problem is with v.sample:
1) it just accepts 1 input raster only.
2) it creates a new vector with a totally new table instead of updating
the attribute table of the input vector with the raster values

A note to 2): Such a procedure is implemented in v.rast.stats.

What do the GRASS devs think about the items 1) & 2)?
Is it a legitimate enhancement?

Kind regards,

[1] http://grass.osgeo.org/grass64/manuals/r.what.html
[2] http://grass.osgeo.org/grass64/manuals/v.sample.html
[3] http://grass.osgeo.org/grass64/manuals/v.rast.stats.html

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