Factor Graph Optimization for Tightly-Coupled GNSS Pseudorange/Doppler/Carrier Phase/INS Integration: Performance in Urban Canyons of Hong Kong

Abstract

The combination of the global navigation satellite system (GNSS) and the inertial navigation system (INS) is extensively studied due to their complementariness. The recently investigated factor graph optimization (FGO)-based GNSS/INS integration positioning showed significantly improved performance in urban canyons, due to the global optimization property and the increased measurement redundancy of FGO, compared with the extended Kalman filtering (EKF) based method. However, only the GNSS pseudorange measurement was utilized in the existing FGObased GNSS/INS integration, and the potential of the Doppler frequency and carrier-phase measurements is still to be explored. To fill this gap, this paper proposed a tightly-coupled GNSS/INS integration via FGO by exploiting the potential of diverse raw GNSS measurements. Specifically, the GNSS pseudorange, Doppler frequency, and time-differenced carrier-phase (TDCP) measurements are integrated with the INS via factor graph optimization. The effectiveness of the proposed method is verified step-by-step using the challenging datasets collected using both automobile-level GNSS receivers in urban canyons of Hong Kong.