I have obtained a flow accumulation map using Arc Hydro tools and obtained the default value in the range of 0-204567. Now I need to change these value by default so that it gives 1 instead of zero. I have tried to reclassify it but I am not getting the range 1- 204567. So for this I have to use a con operation in raster calculator but I don't know what condition to use so that I get a value of 1-204567. How do I specifiy the correct con statement in order to change the value?
If I understand you correctly, by default value, you mean that currently, 0 would represent something like NoData value. In ArcMap, you can change the NoData value of a raster in two ways.
- Add raster as a layer, right-click that layer, select Data -> Export. Make your settings, and under NoData value, change the value to your desired value.
- As pointed out here, you can use a Raster Calculator expression to do this.
This expression assigns a value of 1 if the cell is NoData, otherwise, it retains the original value.
As Vince pointed out, this could cause issues if you have valid values of 1 in your raster. You could explain your situation better to get a better answer on how to proceed.