curvature in GRASS

Hi,

Can anyone tell me how to calculate the real curvature of a surface in
GRASS? Is there a GRASS function for this purpose?
Thanks.

Wen-Ling

Wen-Ling Kuo
Research Assistant, Soil and Water Lab
Department of Agricultural and Biological Engineering
Cornell University, Ithaca, NY 14853
wk14@cornell.edu