Comprehensive evaluation of real-time uncombined-PPP/INS tightly coupled integration with BDS−3 PPP−B2b service in urban environments

Abstract The BeiDou global navigation satellite system (BDS-3) employs the PPP-B2b signal as a data broadcast channel through geostationary Earth orbit (GEO) satellites, enabling the real-time transmission of precise orbit, clock, and differential code bias correction information for BDS and other global navigation satellite systems (GNSS) in the event of network outages. The uncombined precise point positioning (UCPPP) model has gained attention owing to its advantages in multi-frequency and multi-constellation processing. Addressing the challenge of frequent interference and interruption of GNSS signals in densely populated urban areas, this study leverages the complementary strengths of the inertial navigation system (INS) and GNSS, proposing a UCPPP-B2b/INS tightly coupled system and analyzing its positioning performance across various urban environments. Experimental results indicate that the positioning accuracies of the UCPPP-B2b/INS tightly coupled system in urban environments are 33.9 cm, 55.6 cm, and 48.6 cm in the east, north, and up directions, respectively. Additionally, the performance of tactical-grade inertial measurement unit (tactical-IMU) and micro-electro-mechanical systems IMU (MEMS-IMU) was compared under both loosely and tightly coupled configurations using the uncombined approach. The findings reveal that while the positioning performance of the two IMUs is comparable, regardless of whether the PPP-B2b service products or the post-processed precise products are utilized, the tactical-IMU demonstrates superior continuity and anti-jamming capabilities during GNSS signal interruptions. Finally, simulated 30 s GNSS signal outages showed that the tightly coupled PPP-B2b/MEMS-IMU system had positioning errors of 556.8 cm, 547.1 cm, and 99.4 cm, while the PPP-B2b/tactical-IMU system had errors of 6.5 cm, 24.5 cm, and 21.3 cm in the east, north, and up directions, respectively.