Exploring the Utility of Doppler Shift Measurements for Enhanced GNSS Positioning

The Global Navigation Satellite System (GNSS) is critical for a wide range of positioning applications, but limitations in accuracy remain a challenge, especially in dynamic environments. This research explores the potential for improving GNSS accuracy by integrating pseudorange and Doppler measurements, leveraging both GNSS and Low Earth Orbit (LEO) satellite constellations. The study presents a simplified combined solution that incorporates Doppler measurements to estimate user position, velocity, and clock bias rate. Modifications were made to the MATLAB Algorithm Availability Simulation Tool (MAAST) to simulate the improvement to geometry by utilizing both Doppler and pseudorange data, using an almanac of GPS and OneWeb satellites. The results indicate that the combined pseudorange and Doppler solution improves both positioning accuracy and signal availability, particularly in areas with challenging signal geometry. Sensitivity analyses of various Doppler error models reveal that the uncertainty of Doppler measurements has a significant impact on performance. These findings suggest that Doppler measurements can provide notable improvements in GNSS positioning when appropriately integrated, especially in specific scenarios like polar regions or areas with sparse satellite visibility. Future work will focus on refining the solution and error models, as well as expanding the simulations to include other GNSS and LEO constellations and comparing results against other similar solutions and real-world implementation.