LEOS-SOP/INS Integrated Differential Positioning Based on Nonparallel Line-of-Sight Vectors and Orbit Errors Correction

In a Global Navigation Satellite System (GNSS)-denied environment, positioning using low Earth orbit satellite signals of opportunity (LEOS-SOP) offers an effective backup to GNSS. However, the currently available LEO constellations are limited, leading to insufficient visibility. To achieve dynamic positioning, assistance from inertial navigation systems (INSs) is necessary. Since LEO satellites (LEOSs) are not designed for navigation, they exhibit significant orbit and signal emission time errors. To achieve high-precision dynamic positioning, LEOS-SOP/INS integrated differential positioning is required to mitigate the impact of these error sources. However, current research on LEOS/INS integrated differential dynamic positioning has not accounted for the effects of orbit errors or nonparallel line-of-sight vectors, which limits positioning performance. To enhance positioning accuracy, this article proposes a LEOS-SOP/INS integrated differential positioning method based on nonparallel line-of-sight vectors and orbit error correction. This method fully considers the effects of nonparallel line-of-sight vectors due to the low altitude of LEOS and orbit errors, significantly improving differential positioning accuracy. In addition, the relationship between nonparallel line-of-sight vectors and orbit errors with interstation Doppler residuals is analyzed, providing a theoretical basis for evaluating the performance of LEOS-SOP/INS integrated differential positioning. Finally, the effectiveness of the proposed model is validated through vehicular experiments using actual signals from the mature Iridium constellation.