Remote Sensing - Dune Worlds: How Windblown Sand Shapes Planetary Landscapes - page 223

Fig. 18.21 Multi-wavelength Space Shuttle Imaging Radar image of
the Namib near Luderitz. The Atlantic Ocean is at left and the town
itself. In the middle are transverse dunes, and linears inland at right.

The colors indicate the relative contribution of different wavelengths,
which respond to different length scales of roughness. NASA/JPL
image PIA01856