Raster overlays

[AndyMinor]

I have multiple rasters with classified features. I am trying to combine the rasters into a composite so I can have a total area of classified features and know what isn't classified. I want to have my overlay rasters overwrite the cells of the base raster. I have tried map algebra but can't seem to get it right. Does anyone have an idea how to do this? The dataset is too large to convert to polygons and do it the easy way.

Thanks,
Andy

[curtvprice]

I am trying to combine the rasters into a composite so I can have a total area of classified features and know what isn't classified. I want to have my overlay rasters overwrite the cells of the base raster.

Have you tried the Combine tool? The output raster includes every unique combination of values.

Pretty much any combination of cell "replacement" (of course you can't overwrite cells, you make a new raster) can be done using the Con and IsNull tools nested together in various combinations. Search this forum  on  raster calculator or map algebra and you'll see some good examples.