Confusion regarding curvature output values

Discussion created by mbattaglia on Aug 22, 2011
I have been processing curvature rasters from DEMs for inclusion in a wetland delineation model. While the output planform and profile curvatures are easy to understand, I am having trouble grasping the meaning of the output values for the combined curvature raster. I understand how the values are calculated, however, there seems to be inconsistency based on the assumption that
combined curvature = planform curvature - profile curvature as explained in

I have attached a short explanation with an example of the issue I am having a hard time understanding.

If anyone can explain this I would greatly appreciate it.