If your computing a surface from contours I believe s.surf.tps uses the
interpolation method of choice. The inverse distance weighting
of s.surf.idw would give you unsatisfactory results. But maybe
not...
If you convert your sites to raster you can use r.random to extract a
certain percentage, and it will retain attributes..BUT...this may
introduce too much error due to raster conversion...just a thought.
Hope this helps,
--
R. Brian Culpepper Research Assistant
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Center for Advanced Spatial Technologies (fax) 501 575-3846
Rm. 214 Ozark Hall (work) 501 575-6159
University of Arkansas brian@cast.uark.edu
Fayetteville, AR 72701
All opinions are my own and do not necessarily reflect those of the
Center for Advanced Spatial Technologies or the University of Arkansas.