I am currently undertaking my final year dissertation looking at the automatic filtering of a Digital Surface Model to a Digital Terrain Model. In order to try and validate my data I have collected some 'true' height data using GPS. I have managed to load this into ArcMap 10 so that the attribute table has the height value. I was therefore wondering if anybody knew of a way that I could compare the height value collected from the GPS to the value I have for my Digital Terrain Model to see if there is any difference.
You can use the Add Surface Information tool (3D Analyst) to add the elevation values to the attribute table of the point data. There is also the Extract Values to Points (Spatial Analyst) tool that will do that same thing except it will generate a new feature class for the output. Once the values are in the attribute table, you can use the field calculator to determine the difference.