I need you help trying to calculate Topographic Exposure (TOPEX) on a DEM in ArcGIS. I am trying to figure out wind exposure on a DEM with 25m cells. There is a great blog post where someone explains how to do it but he uses GRASS. Jamie Popkin's GIS Blog I thought I would be able to put the same equation into ArcGIS Raster Calculator but it says the equation is invalid. I've tried playing with it as much as I can but I can't seem to make it work.
His first equation is:
r.mapcalc incl4north = "atan(((dem - dem[4,0])) / ((25 * 4)))"
And then he goes on to string a bunch of them together
Does anyone know how the equation should appear in Raster Calculator in ArcGIS Desktop?