基于北斗卫星导航系统非组合精密单点定位算法的精密授时精度研究

全球导航卫星系统(GNSS)精密单点定位(PPP)技术具有操作简单、成本低廉、定位精度高等优点，在精密授时领域得到了广泛应用。针对现有研究中消电离层PPP模型的组合噪声大、卫星系统多采用全球定位系统(GPS)及实时动态场景少等问题，该文采用非组合PPP模型对北斗卫星导航系统(BDS)精密授时精度开展了研究，并利用Kalman滤波静态模型和动态加速模型进行参数估计。给出了静态和实时动态场景PPP处理策略，并利用超快速预报星历保证动态实时性。结果表明：在静态和实时动态条件下，非组合PPP模型精密授时精度均优于消电离层组合PPP模型；在静态条件下，考虑到BDS和GPS定位精度相当，且亚太地区BDS定位精度更高，BDS授时精度略高于GPS；在实时动态条件下，BDS和GPS精密授时精度在2 ns以内，但BDS授时精度略低于GPS，这是由于空间位置精度因子(PDOP)、载体速度突变和环境因素等的影响，而当完成收敛后，两种系统的授时精度相当，其钟差项中误差均在0.3 m以内。

Accuracy of Precise Timing Based on Uncombined Precise Point Positioning Algorithm in BeiDou Navigation Satellite System

Precise Point Positioning (PPP) of Global Navigation Satellite System (GNSS) has the advantages of simple operation, low cost, and high positioning accuracy, and has been widely used in precise timing. Considering the problems of high combined noise of ionosphere-free PPP model, major navigation satellite system being Global Positioning System (GPS), and fewer real-time dynamic scenes in the existing research, the uncombined PPP model is used to study the accuracy of timing in BeiDou navigation Satellite system (BDS). Static and dynamic models of Kalman filter is used in parameter estimation. PPP processing strategies for static and real-time dynamic scenarios are proposed, and ultra-fast forecast ephemeris is used to ensure real time. The results show that: Under static and real-time dynamic conditions, the accuracy of precise timing with the uncombined PPP model is better than that of the ionosphere-free PPP model; Under static condition, considering that the positioning accuracy of BDS and GPS is equivalent, and the positioning accuracy of BDS in the Asia Pacific Region is even higher, the timing accuracy of BDS is slightly higher than that of GPS; Under real-time dynamic condition, the precise timing accuracy of BDS and GPS is both within 2 ns. But owing to Position Dilution Of Precision (PDOP), sudden changes of carrier speed, and environmental factors, the timing accuracy of BDS is slightly lower. And when the convergence is completed, the timing accuracy of the two systems is equivalent, and the clock biases are all within 0.3 m.