SAR True Digital Ortho Map Production for Target Geometric Structure Preservation

Geometric structural information of objects in synthetic aperture radar (SAR) images is of great significance in target detection and analysis. The existing orthorectification methods of SAR images generally follow the traditional routes of optical images, resulting in suffering from the influence of layover, and bring difficulties in image analysis or target extraction without sufficient prior knowledge. Therefore, this article proposes a highest-projection-principle-based SAR true digital ortho map (TDOM) production method for the restoration of geometric structural information of targets. First, ground control information extracted from the high-precision digital surface model is applied to calibrate the geolocation error of original SAR images. Second, the highest projection principle and the visibility detection are utilized to reduce the influence of layover. To preserve the structural information of targets, multiview SAR TDOMs are integrated and compensated to generate a fused SAR TDOM image similar to optical view. Two Gaofen-3 (GF-3) SAR spotlight images are included to verify the performance of our proposed method. Experimental results are compared qualitatively in visual effects and quantitatively in geolocation accuracy. The results indicate that the produced SAR TDOMs can preserve the structural information of targets and provide more similar geometric structural information as optical images, which will effectively improve the efficiency in the interpretation of orthorectified SAR images.