High-Accuracy Urban DEM Using Permanent Scatterers

The permanent scatterers (PS) technique is a powerful operational tool that exploits a long series of synthetic aperture radar data for monitoring ground deformations with millimeter accuracy on a high spatial density grid of pointwise targets. The technique has been applied successfully to a number of applications, from subsidence and volcano monitoring to slow-landslide detection. This paper aims to analyze and demonstrate the positioning capability of the PS technique applied to the generation of urban elevation maps. The problem of the univocal identification of the PS position (discarding pixel-dependent sidelobes, both far and near) is addressed, and an easy and efficient solution is proposed. The results obtained in the Milan site allow the appreciation of the very high quality of an urban digital elevation model retrieved with the PS technique. The ground level of the city is identified with submeter accuracy, and elevated targets, where present, reveal building profiles. The estimated city street level (ranging plusmn3m in 16times18 km
²
) is then compared to those obtained with the same technique using a descending parallel track and an ascending one. Furthermore, the estimated PS elevation with respect to the ground has been connected to temperature-dependent elongations of high structures