DEM Generation by Means of ERS Tandem Data

This paper presents an application of the European Remote Sensing (ERS) satellites' radar data to digital elevation model (DEM) generation. The selected test site is the Sannio-Matese area in southern Italy, where several corner reflectors (CRs) were deployed to be used as ground control points (GCPs) for height measurement accuracy validation. First of all, an analysis of the CR response in radar images is presented. Then, the procedure for image pair geometric registration and interferogram formation is described in detail. A quantitative analysis is also performed by comparing these interferograms to the corresponding products obtained by using the ISAR software, officially distributed by the European Space Agency (ESA). Reported correlation values show that only tandem pairs allow an efficient interferometric processing to be performed, thanks to their short-time baseline (one day), whereas correlation adequate for differential interferometry could not be achieved. The method adopted for the computation of the interferometric baseline components on the basis of satellite orbital data is described, including the GCP-based corrections. The procedure was applied to obtain DEMs of a 10×10 km2 subarea characterized by very high correlation coefficients (0.6). The best attained values of the GCP height measurement accuracy were about 4 m. Finally, the DEMs were compared, giving root mean square (rms) differences less than 20 m in the best case.