"Vector Ruggedness Measure (VRM) measures terrain ruggedness as the variation in three-dimensional orientation of grid cells within a neighborhood. Vector analysis is used to calculate the dispersion of vectors normal (orthogonal) to grid cells within the specified neighborhood. This method effectively captures variability in slope and aspect into a single measure. Ruggedness values in the output raster can range from 0 (no terrain variation) to 1 (complete terrain variation). Typical values for natural terrains range between 0 and about 0.4. VRM was adapted from a method first proposed by Hobson (1972). VRM appears to decouple terrain ruggedness from slope better than current ruggedness indices, such as TRI or LSRI. See Sappington et al. 2007, for further details" (Sappington 2012). After calculating raw VRM values we, binned the values into 6 classes using Jenks Natural Breaks for use in the Land Treatment Exploration Tool Similarity Index. Classes range from very low to very high.