Missing acreage after Combine of 3 raster grid files

Discussion created by nmaggiul on Jul 7, 2010

I am trying to figure out where ~3,000 acres of the original area I am analyzing went after running a Combine in the Spatial Analyst Tools/Local/ section of the toolbox.  I'm not sure if it is common to have discrepancies in area of about this size when converting to raster and then combining several datasets using the Combine tool?  I am wondering if it has something to do with the orientation of the pixels in each dataset and then how they line up together, maybe if a certain percentage of the pixel doesn't overlap the pixels for the other two datasets then the area is kicked out of the combined attribute table?

I noticed only slight differences in the raster files I combined:

Raster 1: 643,445 acres
Raster 2: 643,056 acres
Raster 3: 643,474 acres (but left as a larger file for the Combine)

Combined they give me: 640,524 acres and I should have closer to 643,477 acres. 

Please pass along any ideas/advice.