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i have the following formula:

L = (l/22,1)^m

(l = Flow length)

m is calculated like this:

m = 0,5 when slope is >4 degrees

m = 1,2 * sin^1/3a when slope is <4 degrees (a = slope in degrees)

I already have the slope_deg and flow_length layer. Now I want to enter the formula to the raster calculator. I am new into ArcGIS and I dont know how i can implement it.

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@Aaron I'd guess that @Max is from a country with a comma as the radix point, so when he says m = 0,5 he means m = 1/2. – dmahr Apr 1 '13 at 0:04
@Aaron I think it means L = (l/22.1)^m – dmahr Apr 1 '13 at 2:09

You can incorporate Con into your raster algebra equation to make this calculation. Alternatively, use the Con (Spatial Analyst) tool. The following links will help you build the Con expression:

Conditional evaluation with Con

Building expressions in Raster Calculator

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