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。

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.