GPS-Denied Navigation Using SAR by Measuring Position Fitness Using Image Quality Measures

Due to the risk of GPS signals being blocked, jammed, or spoofed, there is a great need for alternative methods of navigation. This paper presents an algorithm for augmenting IMU-based navigation in GPS-denied (GPS-D) environments using a synthetic aperture radar (SAR) system where the SAR image is formed by the backprojection (BP) algorithm. The GPS-D SAR algorithm exploits the dependence of the BP algorithm on the position of the radar platform. An image quality measure is determined, where a better score corresponds to a SAR image being formed with more accurate position data. This image quality measure is used in the GPS-D SAR algorithm to correct position errors. The algorithm is tested on real SAR data with associated GPS positions, and the results are analyzed. The algorithm is determined to have variable performance depending on the parameters of the algorithm and the particular noise added to the position data.