GPS/BDS Real-Time Precise Point Positioning for Kinematic Maritime Positioning

Real-time precise point positioning (PPP) has been evolved as a powerful technique to achieve globally homogenous decimeter or even centimeter positioning accuracy, which is widely used for maritime precise positioning applications. Currently, the research of the real-time PPP for maritime applications mainly focuses on GPS and GLONASS. In addition, the real-time PPP for kinematic maritime positioning is at least limited by two issues, (i) The real-time availability of the correction products for satellite orbits and clocks; (ii) The error correction related to the marine environment, especially for the estimation of wet zenith troposphere delay (ZWD) is challenged by complex fluctuations of marine atmospheric weather and the severe multipath caused by the sea clutter reflection. In this contribution, using the State-Space Representation correction products based on Radio Commission for Maritime Services (RTCM-SSR), we develop a GPS/BDS real-time kinematic maritime PPP. On the one hand, a piece-wise method is adopted to estimate the ZWD and the horizontal gradient. On the other hand, a robust sequential least squares (RSLSQ) PPP estimator is adopted based on IGG-III model to restrain the unmolded gross error. Based on the 6 h maritime data, the results show that the up direction accuracy and the convergence time of GPS, BDS and GPS/BDS, respectively, are improved based on 0.5 window length for ZWD estimation and the RSLSQ estimator. In addition, the horizontal accuracy of real-time single BDS and GPS using RTCM-SSR can achieve the accuracy of sub-decimeter level when the positioning error is convergence. Compared with the single constellation, the positioning accuracy and the convergence time of the real-time GPS/BDS using RTCM-SSR improves, respectively, by 10 and 18%, and the kinematic positioning accuracy in horizontal is better than 30 cm.