LEO enhanced Beidou PPP-RTK positioning method and experimental analysis

Low earth orbit (LEO) constellation has the advantages of large number of satellites and rapid change of geometric configuration, which is conducive to the rapid convergence of ambiguity parameters in precise single point positioning (PPP). However, it is difficult to achieve rapid convergence of ambiguity in several seconds or even instantaneous because of the influence of atmospheric delay. In this contribution, a LEO constellation enhanced PPP-RTK method is proposed, which makes full use of the high-precision atmospheric information and ambiguity resolution (AR) method to further improve the positioning performance of Beidou. A polar orbit constellation containing 192 LEO satellites was designed, and the observations of 22 ground stations were simulated. After estimating the UPD and precision atmospheric delay correction, the positioning performance of LEO enhanced PPP, PPP-AR and PPP-RTK are evaluated respectively. The results show that under the enhancement of LEO constellation, the number of visible satellites increases by 4~6, and the average PPP initialization time of 22 stations is shortened from 552.1 s to 102 s, with the improvement of 81.52%. After the ambiguity resolution, the initialization time is further shortened to less than 1 minute. With the regional network augmentation, the LEO enhanced PPP-RTK can achieve a positioning accuracy of centimeter degree, and the positioning accuracy can be improved by 98.5% compared with PPP. Even when the ground reference network is expanded to 500 km, the LEO enhanced PPP-RTK can still achieve rapid convergence of about 10 seconds.