Raster to Sites

You can create a site file from a raster file using r.to.sites. This will create a site for every non-NULL cell of your raster map. You might want to adapt your region settings to a lower resolution in order to have less sites in the result (see the chapter called The GRASS Region.

Another command that might be useful in this context is s.sample which samples a raster map at the site locations in the input (site) file by either cubic convolution interpolation, bilinear interpolation, or nearest neighbor sampling.