Exploiting Projection Trajectories Discrepancy for Multipath Suppression and Detailed Feature Extraction of Buildings in SAR Adjacent Sub-Aperture Images

In synthetic aperture radar (SAR) imagery of built-up areas, multipath effects generate false targets that closely resemble genuine structural features, severely hindering refined interpretation of building structures. Existing methods based on interferometric SAR, tomographic SAR, or full-angle circular SAR (CSAR), while effective in 3D information extraction, impose stringent requirements on radar systems, data acquisition conditions, and prior information, rendering them less applicable to time-critical scenarios with limited observation constraints. To address this issue, this paper proposes a multipath suppression and detailed feature extraction method for buildings based on projection offset discrepancies across adjacent sub-aperture images. First, a projection offset model for elevated target points and a multipath effect model between elevated targets are established, theoretically revealing that the projections of elevated targets and multipath ghosts are offset to opposite sides of the target in successive sub-aperture images. Building upon this theoretical foundation, a complete image-domain processing pipeline is developed: an improved iterative watershed algorithm for robust building region segmentation, non-edge Hough transform combined with Thresholded Connected Component Analysis clustering for wall line extraction, multi-dimensional feature-based Hungarian algorithm for wall matching and tracking across sub-apertures, and normalized cross-correlation (NCC) for pixel-level offset estimation. Based on the distinct offset characteristics, building structures are categorized into three classes—stationary walls, elevated structures, and multipath ghosts—enabling simultaneous multipath suppression and structural extraction. Experimental results on Ku-band UAV-borne circular SAR data demonstrate that the proposed method requires only a small number of sub-aperture images with narrow angular spans to effectively distinguish different scattering structures, suppress multipath ghosts, and extract major structural details, providing a viable solution for building interpretation in SAR imagery under observation-constrained scenarios.