Con/Boolean, Calculation with NoData Values

Discussion created by jradinger on Jan 12, 2011
Latest reply on Jan 14, 2011 by jradinger

I have just a logical problem which is (so I think) quite easy to solve but I still don't know how:

I have a 2 raster files:
1) a total river in a raster format (river=value 1, else=NoDatavalue),
2) an upstream part of the same river (riverpart=value 1, else=NoDatavalue), the downstream part isn't existing (also NoData)

I want to get the downstream part of the river. E.g. a raster would be nice where the upstreampart is +1 and the downstreampart is -1.

The logic behind is:
where upstreampart is 1 and total river is 1 there should be +1,
where upstreampart=Nodata and total river = 1 there should be -1
and where both raster are NoData there should be NoData

I really don't know how should I do that..
If necessary I can post the two rasters....