raster - Converting DEM into areas of "flatness", with arbitrary fill/cut to area ratio?

I want to find areas of relative "flatness" in a DEM.

How can I find flat areas?

I want to find a neighbourhood of contiguous cells that have an elevation variance that is within a certain tolerance threshold.

I can use the ESRI suite of tools, or any open source GIS.

Answer

If you're looking for a region of specific size and area:

1. As before, classify your cells by the slope.


2. Then do a Region Group on the raster. The count value will give you area values for the raster.


3. Then if you need regions of a certain width (ie, not something long and thin) run Zonal Geometry with the Thickness option, which will give you the radius of the largest circle that can be drawn within the zone.