Raster Math and no data

Discussion created by ryanknisley on Aug 9, 2012
Latest reply on Aug 9, 2012 by slynch-esristaff
I have created a raster from a polygon and am trying to add the cell values of this raster to an existing underlying DEM.  I have tried "Plus" in Raster Math and Combine and Weighted Sum in Spatial Analyst Overlay tools.  Each time it removes the cells of the underlying DEM when there is no data for the raster I am adding. Why wouldn't any of these processes have an option to count no data from one or either of the rasters as ZERO?   I want to keep all the cells from the existing underlying DEM, but only add the cell values of the raster I created where they overlay. 

The only thing I can think of now is to create a polygon that encompasses the raster I created from the original polygon, union them so I can then assign a value of zero to the polygons where there was no data before, and then rerun my polygon to raster.... what a hassle.  Any other ideas?