GNSS广域差分改正数估计方法研究

随着我国北斗三号基本系统的正式运行，基于地面监测站的广域差分增强系统成为进一步提升卫星导航定位精度的手段之一。在码噪声多径误差修正（CNMC）的基础上，使用等效钟差方法实现GNSS卫星轨道与钟差误差的解耦，并依据卫星轨道运动的动力学特性，引入希尔差分方程描述卫星轨道误差变化，实现对轨道误差的实时卡尔曼滤波估计。基于GPS实测数据，对改正前后的用户等效测距误差（UERE）和定位精度进行了对比研究。实验结果表明，采用该方法，UERE标准差由改正前的0.456 m减小至0.227 m，降幅达到50.22%；整体水平定位误差（95%置信区间）由0.981 m减小至0.782 m，垂直定位误差（95%置信区间）由1.991 m减小至1.131 m，分别提升了20.29%和43.19%，差分改正效果明显。

Research on GNSS wide-area differential corrections estimation method

With the operation of the BeiDou-3 in China, the wide-area differential augmentation system based on the ground monitoring station has become one of the means to further improve the accuracy of satellite navigation and positioning. On the basis of code noise multipath error correction (CNMC), the equivalent clock bias method is used to decouple the orbit and clock error of GNSS satellites, and according to the dynamic characteristics of satellite orbital motion, Hill differential equations are introduced to describe the orbital error changes of satellites, so as to realize the real-time Kalman filter estimation of orbital error. Based on the GPS data, the user equivalent ranging error (UERE)and positioning accuracy before and after correction are analyzed. The results show that by using the proposed method, the standard deviation of the UERE is reduced from 0.456 m to 0.227 m, and the decrease rate reaches 50.22%, the horizontal positioning error (95% quantiles) is reduced from 0.981 m to 0.782 m, and the vertical positioning error (95% quantiles) is reduced from 1.991 m to 1.131 m, which are increased by 20.29% and 43.19%, respectively, and the difference correction effect is obvious.