interpolation programs

[Simon Cox]

Are there any interpolation programs for grass out there EXCEPT 
the idw pair?  

Inverse distance weighting may be fast and easy, but 
it does not produce very good results for some types of problem - 

eg if you have a "surface" which you *know* is smoothly varying, 
(eg geophysical data)
then some form of surface fitting (polynomial, spline, etc) can be 
better - it allows you to find peaks between the data points, whereas the 
idw algorithm will NEVER produce a value higher (or lower) than 
the surrounding values.

Thanks for your assistance

Simon Cox
Dept of Earth Sciences
Monash University
Clayton,  Vic  3168   Australia