Automatic generation of large scale ERS DEMs and displacement maps

To generate large-scale digital elevation models (DEMs) and displacement maps from interferometric SAR (InSAR) data, the operator intervention must be minimized. One labour intensive processing step is traditionally utilization of tiepoints. For ERS, however, ground control points (GCPs) can be tied accurately to radar line number and range pixel without operator intervention. By combining precision orbit data with the time-tagging information accompanying raw ERS SAR data, the pixel location of a GCP with a known latitude, longitude, and height can be calculated. In this paper an assessment of the stability of the critical ERS radar parameters, which are slant range offset and azimuth line time-tags, will be given. Experiments have shown that, for the major part of the tandem period, the relative accuracy of ERS-1/2 tandem data is 1.2 m rms. for the slant range offsets, and 5.3 m rms. for the azimuth time-tags, including both uncertainties in the radar parameters, orbit data, and estimation noise. The absolute precision of the mapping from geographical coordinates to slant range geometry is with the presented method estimated as being better than 10 m on ground.