[GRASS-user] Sampling multispectral data

[Markus Neteler]

Hi Ned,

On Wed, Feb 4, 2009 at 11:45 AM, Daniel Victoria
<daniel.victoria at gmail.com> wrote:
> Check out r.what manual page [1], specially the part about using input
> from a text file or, better yet, sending the output from v.out.ascii
> to r.what.

another option may be:

 v.what.rast: Uploads raster values at positions of vector points to the table.
 http://grass.osgeo.org/grass64/manuals/html64_user/v.what.rast.html

Additionally, in GRASS >= 6.4 you can do a selective random sampling
with v.extract:
 http://grass.osgeo.org/grass64/manuals/html64_user/v.extract.html
 v.extract ...
 random=integer
    Number of random categories matching vector objects to extract
    Number must be smaller than unique cat count in layer
 -> Example: Extract 3 random areas from geology map

Combining these modules you'll be able to perform the extraction.

Markus

PS: Please consider (later) to create a small FAQ in the GRASS Wiki -
      solved once, solved "forever"...