Analysis of an Airborne SAR Interferometer

This paper presents the analysis of C-band cross-track interferometric data (XTI) acquired by the TOPSAR system, on­ board the NASA/JPL DC-8 aircraft, during the MAC Europe 1991 Campaign over the Matera test site (Southern Italy). The main technical aspects of interferometric processing, from raw data compression to DEM generation, have been addressed starting from the analysis of the collected raw data, compressed with a range-Doppier SAR processor which accounted for range migration effects and antenna squint. The phase difference map (interferogram) has been obtained after co-registration performed by using ID cross-correlation techniques. The airplane attitude angles, recorded by the navigation system, have been used to derive the baseline time variation, necessary for the 2r ambiguity solving procedure. The ±0.2 mm accuracy on the estimate of the baseline components gave a theoretical rms error on the height of ±2.5 m for distributed targets, and ±4.5 m for point targets. Finally, the computed terram elevation has been compared with the 1:25,000 scale digitised contour levels of the Istituto Geografico Militare Italiano (IGMI), in order to assess the height accuracy of the system. The rms errors on the height estimate have been found to be ± 15 m for point targets, and ±8 m for extended targets.