Analysis of Doppler positioning with LEO and MEO satellites.

The integration of Low Earth Orbit (LEO) satellites into Position, Navigation, and Timing (PNT) frameworks offers an opportunity to enhance and complement Global Navigation Satellite Systems (GNSSs). In particular, this study focuses on employing Doppler-based positioning techniques. An innovative reduced-parameter Doppler positioning algorithm is proposed, and it is compared to the conventional linearized least-squares approach. The findings show that the proposed algorithm leads to better Dilution of Precision (DOP) and improved accuracy. Both algorithms have been tested using simulated data within a hardware-in-the-loop framework, incorporating measurements from both GNSS and LEO satellites. The study highlights a key limitation of GNSS Doppler positioning when used alone: Medium Earth Orbit (MEO) satellites, which are typical of GNSS, move relatively slowly, thereby affecting the Doppler effect and consequently reducing positioning performance. The introduction of faster-moving satellites such as those in LEO leads to enhanced Doppler-based positioning accuracy. The results underscore the substantial impact of LEO satellites in augmenting GNSS capabilities, with error reduced to approximately ten meters. This integration significantly boosts positioning performance, offering users a more reliable and precise navigation solution.