/usr/bin/gdaldem

 Usage: [--help] [--help-general]
 - To generate a shaded relief map from any GDAL-supported elevation raster :

     gdaldem hillshade <input_dem> <output_hillshade>
                 [-z <zfactor>] [-s <scale>]
                 [-az <azimuth>] [-alt <altitude>]
                 [-alg ZevenbergenThorne] [-combined | -multidirectional | -igor]
                 [-compute_edges] [-b <Band>] [-of <format>] [-co <NAME>=<VALUE>]... [-q]

 - To generates a slope map from any GDAL-supported elevation raster :

     gdaldem slope <input_dem> <output_slope_map>
                 [-p] [-s <scale>]
                 [-alg ZevenbergenThorne]
                 [-compute_edges] [-b <band>] [-of <format>] [-co <NAME>=<VALUE>]... [-q]

 - To generate an aspect map from any GDAL-supported elevation raster
   Outputs a 32-bit float tiff with pixel values from 0-360 indicating azimuth :

     gdaldem aspect <input_dem> <output_aspect_map>
                 [-trigonometric] [-zero_for_flat]
                 [-alg ZevenbergenThorne]
                 [-compute_edges] [-b <band>] [-of format] [-co <NAME>=<VALUE>]... [-q]

 - To generate a color relief map from any GDAL-supported elevation raster
     gdaldem color-relief <input_dem> <color_text_file> <output_color_relief_map>
                 [-alpha] [-exact_color_entry | -nearest_color_entry]
                 [-b <band>] [-of format] [-co <NAME>=<VALUE>]... [-q]
     where color_text_file contains lines of the format "elevation_value red green blue"

 - To generate a Terrain Ruggedness Index (TRI) map from any GDAL-supported elevation raster
     gdaldem TRI <input_dem> <output_TRI_map>
                 [-alg Wilson|Riley]
                 [-compute_edges] [-b <band>] [-of <format>] [-co <NAME>=<VALUE>]... [-q]

 - To generate a Topographic Position Index (TPI) map from any GDAL-supported elevation raster
     gdaldem TPI <input_dem> <output_TPI_map>
                 [-compute_edges] [-b <band>] [-of <format>] [-co <NAME>=<VALUE>]... [-q]

 - To generate a roughness map from any GDAL-supported elevation raster
     gdaldem roughness <input_dem> <output_roughness_map>
                 [-compute_edges] [-b <band>] [-of <format>] [-co <NAME>=<VALUE>]... [-q]

 Notes :
   Scale is the ratio of vertical units to horizontal
    for Feet:Latlong use scale=370400, for Meters:LatLong use scale=111120