I am now working on mapping some diseases in state A. I have all the layers (same projections, same raster, eveything is pretty much similar).
Some the layers (ie layer A1 and B2) do not have the values for the whole state, for example - layer A1 contains sparse values, which indicate that the observations are done at certain places (and not the whole state). For the counties that do not have values, there are no zeros or null. They are just empty.
When I tried to do Weighted Sum Overlay for all the layers, the resulting map is somehow distorted in the same areas with the empty cells (values, whatever).
I've tried to put all zeros in the missing values cells and summing them up with other layers but it's not working. What could possibly go wrong, and how do I rectify this?