I have a DEM layer in ArcMap 10.2 which I then clipped to fit a large shapefile. I'm trying to find the area of the new DEM shape using the Image Analysis tools, specifically the Mensuration tools. I keep getting an error message "Not all points are in the current image". I haven't used these tools before and I'm relatively new at working with DEMs. Is there a better tool to use or a different process for measuring DEM files?