中文摘要：

差分码偏差（Differential Code Biases,DCB）参数作为导航电文中重要的一项,是影响用户PNT服务的主要误差源之一。北斗卫星导航系统（后文简称＂北斗系统＂）发射三个频点的导航信号,在导航电文中需要发播卫星的2个TGD（Timing Group Delay）参数。文章首先介绍了北斗系统卫星DCB参数最小二乘解算与形式误差评估;其次根据北斗系统三频特点,提出了不同频点组合计算垂直方向电离层电子总含量（VTEC）互差的DCB精度定量评估方法,并与IGS（International GNSS Service）提供的GPS卫星DCB精度进行比较;最后,详细分析了DCB参数精度对用户等效距离误差（UERE）计算和定位计算的影响,分别采用卫星出场标定DCB参数和经过解算DCB参数进行评估。实测数据分析结果表明,北斗系统卫星DCB参数解算形式误差与IGS解算GPS卫星DCB参数形式误差相当,但受卫星类型和解算测站的几何分布限制,北斗系统卫星DCB参数解算不确定度相比IGS略差,估计精度优于0.5ns,不同频率组合计算VTEC互差绝对值均值优于0.6TECU。相比采用卫星出场标定值,采用系统解算DCB参数后,双频用户三维位置误差改善13.80%～47.42%。

英文摘要：

As an important part of GNSS navigation message,the differential code bias（DCB） parameter is one of the main error sources affecting the PNT services.COMPASS provides navigation signals on three frequencies,and broadcasts two TGD parameters.An algorithm to solve COMPASS satellites DCB parameters and their form error was introduced.According to the COMPASS tri-frequency characteristics,a new method using different dual-frequency combinations was proposed to evaluate the accuracy of DCB parameters.DCBs provided by manufacturers and DCBs solved by the algorithm are taken to analyze the effects on UERE and positioning accuracy.Real data analysis indicates that the form error of COMPASS satellite DCBs and GPS satellite DCBs share the same accuracy,however,influenced by the satellite constellation and regional distribution of stations,the stability of COMPASS satellite DCBs is worse than that of GPS satellite DCBs from IGS.The accuracy of COMPASS satellite DCBs is better than 0.5 ns,and the difference of VTEC between different calculations using two kinds of geometric-free combinations is better than 0.6 TECU.Compared with DCBs provided by manufacturers,dual-frequency user′s 3D positioning accuracy is improved from 13.80% to 47.42% by using DCBs from the algorithm.