A Twofold Stereo Positioning Method for Multiview Spaceborne SAR Images

The traditional auto-calibration of synthetic aperture radar (SAR) images based on the range-Doppler (RD) model couples the coordinates of ground target points (GTPs) and the slant range correction to solve, resulting in unstable solutions. This letter proposes a twofold positioning method (TPM) for multiview spaceborne SAR images to solve this problem. In order to obtain the more precise coordinates of GTPs and the stability of the solution, the conjugate gradient method (CGM) is performed to the initial and secondary positioning for the normalized RD model. Compared with the traditional least squares method (LSM), the accuracy of TPM is on average 13.47% higher with the YaoGan-SAR satellite (150 MHz and 24.4 mu s), and 44.38% higher with the YaoGan-SAR satellite (200 MHz and 24.4 mu s). In addition, the stability of the method is improved. The experimental results based on the YaoGan-SAR satellite images verify the effectiveness of the method.