Preliminary assessment of SRTM X band DEMs of Southern Africa for hydrogeological studies

The Table Mountain Group (TMG) Aquifer Feasibility Study and Pilot Project is a major hydrogeological project in the mountains fringing the eastern side of the Cape Town metropolitan area. An earlier study using a 30 m×30 m DEM demonstrated that the TMG topography is spatially and structurally well correlated with the patterns of fracture deformation, partly inherited from the break-up of the Gondwanaland supercontinent, in part produced by uplift and erosion under the present-day plate-tectonic stress regime. The advent of the SRTM datasets seems thus to be potentially a good source of high resolution DEM data for such applications, but the differences between radar derived and stereo optical data must be assessed. For example, and is shown, X Band radar data is sensitive to the height of vegetation. Although, not as important for this application, the absolute height accuracy of the X Band DEMs is also assessed via a corner reflector deployed during the mission, as well as other spot heights.