精密单点定位（PPP）收敛时间长达20~30分钟，极大限制了其在时效性要求较高领域的应用。多频率北斗卫星导航系统的迅速发展，为PPP快速收敛带来了新的前景，但同时也产生了一系列需要解决的难题，如IGS双频卫星钟差并不适用于多频组合。本项目拟开展顾及频率间卫星钟偏差（IFCB）的北斗多频融合PPP理论与方法研究。具体地，引入抗差估计精化随机模型，提出北斗卫星IFCB估计方法，根据模型系数和太阳-卫星-地球相对几何之间的内在联系，建立高精度的IFCB模型；研究IFCB和接收机钟差、卫星钟差、电离层延迟、相位模糊度等参数的相互耦合机制，提出能兼容多种观测值组合的IFCB改正方法；研究模糊度固定成功率的影响因素，并利用多频数据的优势，发展部分模糊度快速固定方法，使PPP技术在全球范围内具备快速收敛到厘米级精度的定位能力。研究成果对于提升北斗精密位置服务性能具有重要意义。

The convergence time of precise point positioning (PPP) is as long as 20-30 minutes, which significantly limits its applications in time-critical fields. The BeiDou Navigation Satellite System (BDS) with multi-frequency transmissions is booming, which opens new prospects for the rapid convergence of PPP. But at the same time, there are many problems that need to be solved, such as the inconsistent use of IGS dual-frequency satellite clocks for multi-frequency combinations. This project will focus on the theory and method of BDS multi-frequency integrated PPP in consideration of inter-frequency clock bias (IFCB). We will propose the precise estimation approach for BDS IFCB, in which the robust estimation is introduced to refine the stochastic models. We will establish the high-accuracy models for BDS IFCB based on the internal relations between modeling coefficients and relative sun-spacecraft-earth geometry. After fully investigating the mechanisms of mutual coupling between IFCB and estimated parameters including receiver clock offset, satellite clock offset, ionospheric delay and phase ambiguity, we will propose the IFCB correction method compatible with various multi-frequency PPP models. We will develop the rapid partial ambiguity resolution, in which the negative effects of influence factors on the successful ambiguity-fixing rates are avoided and the advantages of multi-frequency integration are used, so as to reach the goal of converging to centimeter-level positioning accuracy on a global scale within a few minutes for PPP. The research findings mean a significant performance improvement for the BDS precise positioning services.