Abstract:
Objectives Ultra-rapid satellite clock products constitute the prerequisite for providing high-precision precise point positioning (PPP) services to users operating under limited or unstable network conditions. The stability of satellite clock estimates, which is strongly influenced by the choice of clock datum, plays a critical role in determining PPP positioning accuracy. In conventional ultra-rapid satellite clock batch estimation, a single fixed receiver clock is commonly adopted as the reference datum. However, receiver clock noise inevitably introduces instability into the reference clock, thereby degrading the stability and reliability of the estimated satellite clocks.
Methods To address this issue, an optimized clock datum method based on quasi-stable constraints of receiver clocks is proposed. The method constructs a robust local barycentric datum for a group of receiver clocks by introducing quasi-stable constraints weighted according to the accuracy of receiver clock models. By reducing the dependence on a single reference receiver and mitigating the impact of receiver clock noise, the proposed datum enhances the robustness and stability of satellite clock batch estimation. The method is integrated into the satellite clock batch processing framework to improve the overall quality of ultra-rapid satellite clock products.
Results One month global positioning system satellite clock batch estimation experiments were conducted using global tracking network observations. Comparative analyses between the traditional fixed single-receiver clock datum and the proposed optimized datum were performed for different satellite types, including BLOCK IIF Rb, BLOCK IIF Cs, BLOCK IIR Rb, BLOCK IIR-M Rb, and BLOCK III Rb. The results demonstrate that the satellite clock model fitting accuracy is improved by 43.10%, 1.73%, 23.47%, 16.34%, and 47.49%, respectively. In addition, the frequency stability at 1 000 s is enhanced by 9.59%, 0.04%, 0.35%, 0.33%, and 11.22%, while the frequency stability at 10 000 s is improved by 11.53%, 0.60%, 7.62%, 4.83%, and 18.21%, respectively.
Conclusions The proposed clock datum optimization method effectively suppresses the adverse influence of unstable reference receiver clocks on satellite clock batch estimation, particularly under unfavorable conditions where receiver clock stability cannot be guaranteed. As a result, the stability of ultra-rapid satellite clock products is significantly improved, which in turn enhances satellite clock prediction performance and PPP positioning accuracy. This method provides a robust and practical solution for high-precision PPP applications relying on ultra-rapid satellite clock products.
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