As part of my dissertation, I put together several programs that help GRASS (4.1 and beyond) develop uncertainty models of spatial data. I hope you find it useful and dependable. The following papers might clarify their use:
"Visualizing Spatial Data Uncertainty Using Animation (final draft)," by Charles R. Ehlschlaeger, Ashton M. Shortridge, and Michael F. Goodchild. Submitted to Computers in GeoSciences in September, 1996, accepted October, 1996 for publication in June, 1997.
"Modeling Uncertainty in Elevation Data for Geographical Analysis", by Charles R. Ehlschlaeger, and Ashton M. Shortridge. Proceedings of the 7th International Symposium on Spatial Data Handling, Delft, Netherlands, August 1996.
"Dealing with Uncertainty in Categorical Coverage Maps: Defining, Visualizing, and Managing Data Errors", by Charles Ehlschlaeger and Michael Goodchild. Proceedings, Workshop on Geographic Information Systems at the Conference on Information and Knowledge Management, Gaithersburg MD, 1994.
"Uncertainty in Spatial Data: Defining, Visualizing, and Managing Data Errors", by Charles Ehlschlaeger and Michael Goodchild. Proceedings, GIS/LIS'94, pp. 246-253, Phoenix AZ, 1994.
The following program's source code is in tar format and is available to be downloaded by pressing the appropriate link below. Manual pages of these programs are also available.