Problem with Analyzing LULC data (in raster)

Discussion created by mrobin19 on Feb 10, 2011

I am trying to analyze some LULC data (in raster format, cell size is 30,30) using spatial analyst. I'm doing this for several watershed catchments. When I run analyst and get my output table, I add up the areal values for each of the LULC types to get a total area. I then compare that to the area of the catchment polygon.

The problem is the total area calculated by Spatial Analyst (the total of all of the areas of each of the LUCLC types) is way off from the catchment polygon area.

Does anyone have any ideas why this would be?