Changing Window Size for Slope Computations

 I have been comparing slope algorithms, and the results from different software.  I have been looking at 4 algorithms, and a half dozen GIS programs.  Most use a 3x3 window, but one has an option for a 5x5 window.  It turns out I had implemented a 5x5 window in MICRODEM, but never really looked at the results.

This uses a one arc second DEM with about 20,000 elevation postings, which accounts for the jagged histograms below.  This looks only at the three algorithms currently implemented in MICRODEM (the other program has similar results, perhaps not as extreme).

The slopes computed with the 5x5 window are significantly smaller than those with a 3x3 window, and for this scale of DEM should probably not be used.  Perhaps your preferences might be different with a 1 m lidar-derived DEM.





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