Need very urgent help with LS Factor(USLE)Calculation in ArcGis10 (get strange result

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08-12-2012 09:44 AM
JuliaHauczinger
New Contributor
I wanted to calculate the LS Factor of the USLE (Universal Soil Loss Equation) with the tool Raster Calculator in ArcGis 10.
First, I filled my DEM with the tool Fill. (DEM was calculated in UTM)
Second, I calculated the Flow Direction with the Tool Flow Direction.
Third, I calculated the Flow Accumulation with my Flow Direction as Inputfile. [ATTACH=CONFIG]16862[/ATTACH]
Fourth, I calculated the Slope in Degrees by the Spatial Analyst tool Surface and Slope. [ATTACH=CONFIG]16863[/ATTACH]
Fifthly, I used the Equation by Moore and Burch 1986: LS = (Flow Accumulation * Cell Size/22.13)^0.4 * (sin (slope/0.0896))^1.3
Sixthly: I typed in the raster calculator the equation:

(Power((("FlowAcc" * 92.46745509) / 22.13),0.4)) * (Power((Sin("Slope_Degree" / 0.0896)),1.3))

But my result look very very strange! There a lot of white areas! The Raster is not like cover areas.... It looks like that every calculated value is seperated... It looks like a dotted map....What did I wrong?? Did I forget something?? I can`t believe that this is right??!! [ATTACH=CONFIG]16864[/ATTACH]
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10 Replies
SushreeSangitaDash
New Contributor

Hey @JuliaHauczinger ,

Your formula is correct. Just use the slope in radians (i.e., multiply the slope(in degrees) with 3.14/180 ).

Then you will be getting the correct result.

Thank You

 

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