A Dynamic Continuous Constrained Phase Factor Graph Optimization Method for GNSS Kinematic Precise Point Positioning

Carrier phase measurements play a more critical role in achieving precise positioning for lower noise and insensitivity to multipath error over code (pseudorange) measurements. Real-time kinematic (RTK) is the most used precise positioning technique. However, the application costs are increased due to the demands for differential base stations. The undifferenced precise point positioning (PPP) does not require differential station assistance but is typically for static use. This article proposes a dynamic continuous constrained phase (DCCP) method based on factor graph optimization (FGO) for kinematic positioning without differential stations, even in the presence of cycle slips. The precise velocity estimated via integral Doppler and the time correlation of phase ambiguity are regarded as the probability constraints in the factor graph. A real-world experiment was carried out to verify the feasibility of the DCCP method. Experimental results show that the proposed method had a better performance than the kinematic PPP method and the window carrier phase (WCP) optimization method with 0.034-m standard deviation (STD) and 1.338-m mean error. It is our hope that this approach provides new insight into the study of other time-correlated state estimation problems.