Currently I am working on a project dealing with terrain analysis based on a DEM. I came across the term "roughness index" using slope values from that specific DEM. On YouTube I found a video, which showed how to do it in ArcGIS using Focal Statistics:
- Creating a slope map based on the DEM.
- Using focal statistics to calculate mean, min and max within a 3x3 cell raster for the whole DEM.
Using raster caclulator with this expression:
(mean_elevation - min_elevation) / (max_elevation - min_elevation)
- The outcome is called Surface roughness index.
I don't understand why this formula is used.
Why do I have to subtract the minimum elevation from the mean and divide this by the minimum elevation subtracted from the maximum?
Has anyone another (scientific) reference for working with roughness values as standard deviations of slopes?
I have access to ArcGIS 10.4 and QGIS.