The requirement for a global 1km Digital Elevation Model is currently being addressed by the generation of a number of global digital elevation models such as the GLOBE dataset. However, the availability and quality of input ground truth varies widely over the earth’s land surface. There is thus an urgent need for additional independent information both to validate GDEMs and to augment the existing ground truth. At this spatial scale, altimetry presents an attractive option, with the combination of near polar orbit and close track spacing during the ERS-1 geodetic mission providing data at a spatial scale of several km. However, to interpret these data effectively over land requires sophisticated postprocessing.

The ERS-1 mission resulted in the acquisition of large volumes of echoes over non-ocean surfaces. The dense data coverage generated from the geodetic mission offers the possibility of generating millions of height points over the earth’s land surface. However, highly complex altimeter echoes are observed over much of the terrain not sampled by previous altimeters due to loss of lock. An expert system has therefore been developed to retrack individual waveforms using a range of retrackers specifically configured to interpret echoes over land. Data from the entire geodetic mission has been processed to generate a Regional Altimeter Result database (RAR) and this paper presents results illustrating the potential of this technique to generate terrain related information over remote areas. The results confirm the value of an expert system approach to land altimetry retracking, and demonstrate that additional terrain related information may also be derived.