BDS-3/Galileo四频广域单测站快速厘米级定位模型研究

Precise point positioning, which has great development potential and broad application prospects, has gained wide attention due to its flexible positioning mode. However, it is still difficult to meet the requirements of fast centimeter-level positioning application scenarios in a wide area. The release of the BDS-3 and Galileo four-frequency observations provides effective data support and makes it possible to solve the above difficultly. This project aims at achieving fast centimeter-level positioning accuracy for single station in wide area, and constructs a reasonable and feasible technical scheme. The following key issues are focused on: 1) The characteristics of the constructed cycle-slip detections based on four-frequency geometry-free phase combination and four-frequency phase/pseudorange combination are analyzed, respectively, and then the optimal scheme of four-frequency carrier phase cycle-slip detections is formed; 2) The selection strategy of phase fractional cycle bias datum and independent ambiguity datum is optimized, and then the parallel computing and iterated Kalman filter based on single-observation are introduced to construct the network-based estimation model for four-frequency phase fractional cycle bias; 3) A fast precise point positioning ambiguity resolution scheme using four-frequency observations is constructed, and the quality control of ambiguity resolution is introduced step by step, mining the advantage of four-frequency observations in fast ambiguity resolution. This project and its achievements are not only helpful to further improve the theory of multi-frequency and multi-system fast ambiguity resolution, but also providing strong technical support for areas without dense reference stations to obtain fast and high-precision location-based services.

精密单点定位以其灵活的定位方式而广受关注，其具有巨大的发展潜力和广阔的应用前景，然而，尚难满足广域范围内快速厘米级定位应用场景需求。BDS-3和Galileo四频观测数据的播发，为上述问题的解决提供了有效的数据支持并使之成为可能。本项目拟以实现广域单测站快速厘米级定位为目标，构建合理可行技术方案，并就如下关键问题进行重点研究：1）研究四频相位几何无关组合周跳检测量和四频相位/伪距组合周跳检测量特性，构建四频周跳检测量优选方案；2）优化相位小数偏差基准和独立模糊度基准选取策略，引入并行计算和单观测值迭代Kalman滤波，构建四频相位小数偏差快速网解模型；3）构建四频精密单点定位模糊度快速固定模型，逐级引入模糊度固定质量控制，挖掘四频观测值在模糊度固定方面的优势。项目的开展将有利于进一步完善多频多系统模糊度快速固定理论，为参考站稀疏地区的快速高精度位置服务提供有力的技术支持。

精密单点定位（PPP）能够在全球范围内获得用户在国际地球参考框架下的三维地心坐标，已经成为全球导航卫星系统领域的研究热点之一。然而，当无法获取外部大气增强信息时，全球PPP实现连续稳定的厘米级定位精度通常需要数十分钟，在复杂多路径环境下所需时间更长，严重制约了PPP的广泛应用。本课题以我国北斗卫星导航系统（BDS）和欧盟Galileo系统提供四频（及以上）观测值为切入点，深入研究多频多系统观测值融合在解决广域PPP初始化这一瓶颈问题的潜力，主要开展了以下几个方面的研究工作：（1）从多频伪距和相位观测方程出发，研究多频非组合PPP模型中各个参数之间的数学相关性，推导了伪距频间偏差、系统间偏差和相位偏差的数学表达及其含义，构建了形式统一的BDS-3/Galileo多频非组合PPP函数模型，并针对性的研究了多频周跳探测和验后观测值残差检验；（2）以上述非组合PPP模型得到的多测站浮点模糊度为模型输入，逐级构建超宽巷-宽巷-窄巷相位偏差估计模型，基于迭代Kalman滤波和并行计算优化模型计算效率，推导组合形式的相位偏差映射至各频观测值的线性转换矩阵，分析相位偏差时变特性及其恢复模糊度整周特性的性能；（3）以估计的多频相位偏差和非组合PPP模型为基础，构建了BDS-3/Galileo四频（及以上）非组合PPP模糊度固定模型，研究部分模糊度固定方法及模糊度检验准则，利用超宽巷和宽巷模糊度固定约束下的几何定位模型，分析了BDS-3/Galileo瞬时/短时间内定位性能，并进一步研究了多频信号在窄巷模糊度固定方面的优势。估计出的BDS-3（B1I/B3I/B1C/B2a/B2b）和Galileo（E1/E5a/E5b/E6/E5）各频相位偏差天内稳定度优于0.06周，且BDS-3新信号B1C/B2a和Galileo E6在实现瞬时分米级定位（平面优于20 cm）和厘米级定位中具有明显的优势。本课题的研究丰富和发展了多频多系统数据融合及模糊度固定理论，有利于推动PPP在快速分米级和厘米级定位场景中的应用，对拓展我国BDS规模化应用具有重要的现实意义。