Estimating observable-specific phase biases of GEO satellites from regional CORS to analyze its contribution in PPP ambiguity resolution

Abstract Achieving high-precision positioning and fast convergence has been the objective of Precision Point Positioning (PPP), which is restricted by the integer ambiguity resolution (AR). Recently, the emergence of observable specific code/phase bias (OSB) has gratefully alleviated this phenomenon. However, for the BeiDou Satellite Navigation System (BDS), only MEO/IGSO satellites are applied in BDS PPP-AR, while GEO satellites are generally ignored. It will largely limit the utilization in China or Asia-Pacific region, influencing both the convergence time and the positioning accuracy. To investigate the feasibility of applying GEO satellites for AR, the phase OSB of GEO satellites is estimated through the raw observations in this research. Based on the observations data from regional network in China region, the characteristics of BDS mixed-constellation OSBs are analyzed, and PPP-AR with different processing strategies in both static and kinematic mode are performed. The results indicate that the phase OSBs were relatively stable and the percentage of the estimated residuals for B1I/B3I signals within ±0.15/0.25 cycles were over 95/99% and 92/97% for IGSO and MEO satellites, while GEO satellites were slightly poor, with 89 and 96%, respectively. The average positioning accuracy of static PPP-AR containing GEO satellites was 0.55, 0.56 and 1.43 cm in the east, north and up directions, with improvements of 14.06, 3.44 and 9.48% respect to fixed solutions without GEO satellites. For kinematic mode, when the ambiguity of GEO satellites was solved, the convergence time and the average time to first fix were considerably reduced to 25.51 and 27.12 min, exhibiting the improvement of 26.16 and 14.80% compared to fixed solutions without GEO satellites, respectively. This further demonstrated the considerable applications potential of GEO satellites to regional users.