Innovative Cumulative Intensity Projection Registration for Vertical Shift Calibration in HoloSAR

Synthetic aperture radar (SAR) holography (HoloSAR) is a vital remote sensing technique widely employed in extracting three-dimensional (3-D) scattering information of anisotropic targets. In the case of airborne SAR, factors such as flight trajectory errors can introduce phase errors during the imaging process, thereby degrading the quality of HoloSAR images. This paper modifies the phase gradient autofocus (PGA) method based on cumulative intensity projection registration to improve imaging quality. The proposed method begins with an initial phase calibration using the traditional PGA method. Subsequently, the 3-D imaging results, after preliminary compensation, are projected onto two-dimensional (2-D) planes via cumulative intensity projection. The residual linear phase error is estimated based on the vertical shifts observed in the projection results of different sub-apertures. This error is then corrected by adjusting the imaging results, thereby resolving the issue of vertical shift between sub-apertures. Compared to other mainstream methods, the proposed method offers simplicity in principle and high computational efficiency. Experiments on simulation and GOTCHA data validate the effectiveness of the proposed method.