As a consequence, the scale-dependence of topography of a given planetary object is a key parameter in distinguishing and identifying the various geological processes that affected its surface. In order to calculate the quantitative parameters that describe this scale-dependence, one needs a topographic map, or a Digital Elevation Model (DEM) of the surface at high spatial resolution. Such global topographic maps are generally built from laser ranging, radar measurements or from stereo images col- lected by instruments on board spacecraft. Thanks to orbital remote-sensing, the global topographic maps of the Earth, Mars, and the Moon are now accurately determined at spatial resolu- tions of a few tens to hundreds of meters. The global topographic map of Venus is less precise with a resolution of a few kilometers only and larger uncertainties on absolute altitudes.