The landform classification following Meybeck et al. (2001) presents relief classes, which are cal-culated based on the relief roughness. Roughness and elevation are classified based on a DEM according to static thresholds, with a given window size. The landform classification following Iwahashi and Pike (2007) present relief classes which are classified using an unsupervised nested-means algorithm and a three part geometric signature. Slope gradient, surface texture and local convexity are calculated based on the SRTM30 DEM, within a given window size.
Data available here