According to these, crests are areas with positive and therefore convex plan or profile curvature or both as well as an elevation percentile larger than 0.65 and an elevation range larger than 5.0. Areas of depressions have either an elevation percentile less than 0.4 or a plan curvature smaller than -0.5. Furthermore, flats have a slope gradient, which should be smaller than 3% or 1.35. All other areas not classified as crests, depressions or flats are assigned to be slopes.