SAR Tomography at the Limit: Building Height Reconstruction Using only 3-5 TanDEM-X Bistatic Interferograms

Multibaseline interferometric synthetic aperture radar (InSAR) techniques are effective approaches for retrieving the 3-D information of urban areas. In order to obtain a plausible reconstruction, it is necessary to use more than 20 interferograms. Hence, these methods are commonly not appropriate for large-scale 3-D urban mapping using TanDEM-X data, where only a few acquisitions are available in average for each city. This article proposes a new SAR tomographic processing framework to work with those extremely small stacks, which integrates the nonlocal filtering into SAR tomography inversion. The applicability of the algorithm is demonstrated using a TanDEM-X multibaseline stack with five bistatic interferograms over the whole city of Munich, Germany. A systematic comparison of our result with TanDEM-X raw digital elevation models (DEMs) and airborne LiDAR data shows that the relative height accuracy of two-third buildings is within 2 m, which outperforms the TanDEM-X raw DEM. The promising performance of the proposed algorithm paved the first step toward high-quality large-scale 3-D urban mapping.