A 3-D Imaging Topographical Application of Interferometric Synthetic-Aperture Radar (SAR) Data: Digital Elevation Model (DEM) Extraction

The reconstruction of terrain altimetry by means of interferometric Synthetic Aperture Radar (INSAR) images has been successfully demonstrated in the last few years. This work illustrates the mathematical background necessary for the end-to-end characterisation of a radar-derived Digital Elevation Model (DEM), from SAR image acquisition to the four basic processing stages necessary to obtain the final product, namely, interferometric couple registration, two-dimensional phase unwrapping, height reconstruction and DEM projection in ground-range co-ordinates. As a case study, results obtained with simultaneous INSAR data from a campaign over the Vesuvius volcano (Southern Italy) are presented. In particular, the radar-derived DEM is validated by comparison with available photogrammetric digital terrain models, over a 13-km2 area with height variations from 50 to 1016 meters. Accuracy analysis and error budgets on the Vesuvius DEM give a theoretical rms altimetry error of 18 m, against 39+-26 m obtained by projecting in slant-range a DEM derived from 1:25,000 digitised maps provided by the Istituto Geografico Militare Italiano (IGMI).