Precision Geolocation for High-Altitude Airborne SAR: A Spatiotemporal Adaptive Tropospheric Delay Compensation Approach

Accurate geolocation of high-altitude airborne Synthetic Aperture Radar (HAA-SAR) imagery is pivotal for applications in Earth observation and remote sensing. However, errors in tropospheric delay modeling can severely affect positioning accuracy. Despite numerous existing compensation approaches, these methods inadequately address the complex atmospheric spatiotemporal variations encountered in HAA-SAR systems. This study presents the first comprehensive investigation of spatiotemporal variations of tropospheric delay in HAA-SAR systems, revealing their impact on positioning accuracy. To address these challenges, a Spatiotemporal Adaptive Tropospheric Delay Compensation (SATDC) approach is introduced. The proposed method integrates high-resolution ERA5 meteorological data with ray-tracing techniques, while employing a cross-iterative algorithm to simultaneously optimize target height and delay estimates. The method was validated through flight experiments using an X-band HAASAR system across diverse atmospheric conditions and terrains. Experimental results show that the proposed method improves positioning accuracy compared to existing approaches. Specifically, the SATDC method achieves an average range position mean absolute error (MAE) of 2.24 m, representing a reduction of 33.12% outperforming our previous tropospheric delay compensation work TDC-RD. Furthermore, the implementation of spatiotemporally adaptive compensation reduces the slant range measurement MAE from 12.94 m (without compensation) and 2.97 m (with conventional compensation) to 1.71 m. These findings highlight the method's effectiveness in compensating for tropospheric delay, enhancing the precision and reliability of HAA-SAR geolocation in challenging environments.