How to use the Con Tool

Discussion created by Shaun74 on Jun 18, 2012
Latest reply on Jun 22, 2012 by Shaun74
I am trying to cut streams into my DEM. I have made my streams into rasters with a value of -1 (meters) with the rest of the raster having NoData value. I then want to make a conditional (or should I use Pick) to make a new Raster where the elevation is -1 where the streams are and otherwise have the value of the DEM. I have also tried to make a conditional expression in the Single Output Map Algebra without succes.
Part of my problem is that I simply do not know where you write the expressions (such as "Con(IsNull("Corrected_DEM"),???Original_DEM, "Corrected_DEM")". I use ArcGIS 9.3.1 but have mainly used the toolbox tool "Con".
Can someone explain to a newbie?
Regards Shaun