GPS/Galileo/LEO Uncombined and Ionosphere-Free Combined Precise Relative Positioning and Its Performance Analysis

Abstract

The advantages of low-Earth-orbit (LEO) satellites, such as their high signal strength and rapid geometric changes, provide important opportunities for fast, accurate, and robust precise relative positioning (PRP), especially in medium to long baselines. In this study, based on simulated LEO observations and real global navigation satellite system measurements, we investigated the enhanced effectiveness of LEO constellations on baselines of different lengths using dual-frequency uncombined and ionosphere-free combined models. The results showed that in noncombination float solutions, the baselines can converge in 0.7 min, and the ionosphere-free combination requires approximately 2 min. For noncombination fixed solutions, the LEO satellites can reduce the time to first fix (TTFF) to 2.5 and 7.5 min and improve the ambiguity-fixing rate to 95% and 85%, respectively, in the medium and long baselines. The LEO-assisted Global Positioning System (GPS)/Galileo ionosphere-free combination achieved a TTFF of 1.4 min and an ambiguity-fixing rate of 98% for baselines of different lengths.