Three-dimensional Imaging of Tomographic SAR Based on Adaptive Elevation Constraint

Synthetic Aperture Radar Tomography (TomoSAR) has emerged as a hot research topic in the field of SAR imaging, particularly for three-dimensional (3D) urban imaging in recent years. However, in TomoSAR 3D reconstruction, due to the phase unwrapping difficulty, periodic spectral peaks appear in the reconstruction results of the reflectivity profile along the elevation. This results in errors in estimating the elevation locations of the scatterers and causing layering effects in 3D imaging results, which is the elevation ambiguity. In light of this phenomenon observed in TomoSAR, a method for the adaptive adjustment of the elevation search range is proposed to improve the accuracy of the elevation estimation and reduce elevation ambiguity. In this method, the height of the scene is first estimated, the linear function of the elevation sampling center is subsequently constructed based on the height pre-estimations, and the search radius is finally calculated. Thereafter, the elevation search range of each pixel in the SAR image is determined and updated, preserving the true spectral peaks while isolating the ambiguity peaks. The experimental results for airborne and spaceborne measured data demonstrate that the proposed method significantly improves elevation ambiguity and artifacts-related issues while also improving the spatial concentration and continuity of 3D point clouds