Combining spaceborne SAR images with 3D point clouds for infrastructure monitoring applications

The measurement and monitoring of critical infrastructure elements by remote sensing has become necessary for economical and security reasons. Information provided by remote sensing for infrastructure monitoring is extracted with specific signal processing chains that have to be adapted to the geometric particularities of the structure. In this paper we present in detail the first monitoring results obtained by combining spaceborne synthetic aperture radar (SAR) data with externally measured point clouds describing an infrastructure element. The processing core is essentially based on refocusing each available SAR image on the provided point cloud and identifying the scatterers that can be monitored by means of four dimensional tomography. The key points and limitations which appear in the measurement and data processing are illustrated on two test sites in France: the Puylaurent water-dam and the Chastel landslide. The SAR products used are high-resolution sliding spotlight SAR images acquired in the TerraSAR-X and TanDEM-X missions, whereas the point clouds of the structures were generated using GPS localization, topographic measurements and laser scans. The estimated deformations of the scatterers using the SAR images were in good agreement with available in-situ data provided through regular topographic surveys and embedded measuring systems.