Non-line-of-sight Target Relocation by Multipath Model in SAR 3D Urban Area Imaging

The advancement in the miniaturization technology of Synthetic Aperture Radar (SAR) systems and SAR three-dimensional (3D) imaging has enabled the 3D imaging of urban areas through Unmanned Aerial Vehicle (UAV)-borne array Interferometric SAR (array-InSAR), offering significant utility in urban cartography, complex environment reconstruction, and related domains. Despite the challenges posed by multipath signals in urban scene imaging, these signals serve as a crucial asset for imaging hidden targets in Non-Line-of-Sight (NLOS) areas. Hence, this paper studies NLOS targets in UAV-borne array-InSAR 3D imaging at low altitudes and establishes a multipath model for 3D imaging at low altitudes. Then, a calculation method is proposed for obtaining the multipath reachable range in urban canyon areas based on building plane fitting. Finally, a relocation method for NLOS targets is presented. The simulation and real data experiments of UAV-borne array-InSAR show that the proposed method can effectively obtain 3D images and relocate NLOS targets in urban canyon areas, with errors typically below 0.5 m, which realizes the acquisition of hidden NLOS region information. © The Author(s) 2024.