多模多频全球导航卫星系统差分码偏差统一定义与精确估计方法

The differential code biases are one of the important error sources in the multi-GNSS data processing and has to be corrected as precisely as possible. The main problems of existing methods for differential code biases research is that (1) the definition is skimble-scamble, (2) the estimation is imprecise and (3) the application is inconvenience. In view of this , this contribution will firstly propose an unified definition of differential code biases for multi-GNSS, including BDS, GPS, GLONASS and Galileo based the mechanism of differential code bias and its influence factor which are related to the structure characteristic of navigation signals in multi-GNSS; and then an exact mathematical model for simultaneously estimating of the parameters of all types of differential code biases in current multi-GNSS and the parameters related to the ionosphere; thirdly, an correction methods of satellite and receiver differential code biases are individually developed. The proposed algorithm of differential code biases estimation can not only guarantee the consistency of all types of differential code biases estimates and the convenience of differential code biases application, but also improve the accuracy and reliability of differential code bias of satellite and receiver, respectively. Finally, the software for the estimation of differential code biases base on the proposed algorithm will be developed, and the classical application of differential code biases correction in BDS/GNSS-based precise positioning and ionosphere monitoring will be carried out. . The project is the extending and complementing of applicant’s recent research result, and the corresponding achievement is not only able to provide the important knowledge-base and supports of differential code biases correction, but also to offer technical references for the participation of discussing the unified definition of differential code bias in the frame of international GNSS services. Therefore, the related research has the important theoretical and the practical significance on the multi-GNSS data processing and BDS development.

精确处理和修正差分码偏差是有效利用多模多频全球导航卫星系统观测信息提升GNSS服务和应用效能的前提和基础，现有差分码偏差处理技术存在着“定义不统一、求解不严密、使用不便捷”等突出问题。针对此，本项目拟结合不同导航系统的信号结构特点，通过进一步认识和掌握差分码偏差产生的机理和影响因素，创新性地提出一种多模多频差分码偏差的统一定义和表达方式，构建具备同步估计所有类型差分码偏差参数的严密数学模型，设计面向实时应用的卫星和接收机差分码偏差修正方法，进一步提高卫星和接收机多模多频差分码偏差修正精度和可靠性；在此基础上，通过改进现有的相关数据处理软件，在高精度电离层监测和精密定位领域开展典型的试验应用。. 本项目是申请人已有研究成果的延续和拓展，相关研究不仅可以为差分码偏差精确修正提供重要支撑，还可为我国参与IGS差分码偏差标准制定和产品发布提供技术参考，具有重要的理论和现实意义。

差分码偏差是多模卫星导航系统高精度数据处理所必须要克服的误差源之一。针对此，本项目在全面分析和深入认知导航卫星码偏差产生机制的基础上，充分考虑我国北斗全球卫星导航系统混合星座结构和全星座三频信号特点，创新性提出了基于观测量的非差码偏差统一定义方法；同时，结合区域高精度电离层模型，设计了非差码偏差参数联合估计方法以及编码播发方案；研制了多模GNSS差分码偏差精确估计和产品计算软件；基于全球分布的约200个基准站观测数据，业务化计算GPS、BDS2、BDS3、Galileo和GLONASS码偏差参数产品，正式提交至IGS产品中心向全球科学用户提供服务，成功申请国际IGS电离层分析中心，代号为CAS。. 试验结果显示：以“绝对”参数的形式实现码偏差参数的统一表征，不仅有利于开展实时编码和播发服务，而且不同系统、不同频点类型用户仅需要通过线性变换即可获得相应码偏差改正数，使用十分便捷；CAS和CODE、DLR码偏差产品的互差在0.30ns之内；总体上看，现阶段不同算法估计的码偏差参数基本一致，其精度基本在0.20ns左右，可支持用户实现高精度电离层监测和实时精密定位；CAS码偏差产品不同系统或卫星的月稳定性均在0.15ns左右，现阶段实时播发采用逐天更新的策略是完全可以满足高精度定位要求的。. 本项目研制的差分码偏差估计方法及其业务化产品已成功应用于北斗系统地面运控，支持北斗二号和三号系统群延迟参数计算方法升级优化；应用于华为智能手机，辅助支持手机实现车道级定位；作为IGS例行数据产品对外提供服务，被德国宇航中心、法国空间局、武汉大学、千寻位置等国内外相关机构采用，受到国内外广泛关注。. 以本项目研究成果为基础，项目团队发表学术论文7篇，其中SCI检索4篇，申请发明专利1项，软件著作权1项，培养研究生2名，满足了任务书中的指标要求。

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