====== primary topographic attributes ======

==== gradient ====
==== slope ====
==== aspect ====
==== curvature ====
==== roughness ====
==== hillshade ====
==== specific drainage area ====

===== secondary topographic attributes ======
==== topographic wetness index ====
==== stream power index ====
==== compound topographoc index ====
==== sediment transport capacity index ====
==== radiation and temperature indices ====
====== other descriptions ======
====frequency spectrum =====
==== fractal dimension ====