多频多GNSS卫星相位偏差估计与播发形式优化的方法研究

Nowadays, integer ambiguity resolution enabled precise point positioning (i.e. PPP-RTK) represents the most cutting-edge GNSS (Global Navigation Satellite System) precise positioning technique. Its development and applications are, however, subject to the accuracy and effectiveness of the satellite phase bias (SPB) corrections. With respect to SPB estimation, the customary methods rely mainly upon the precise satellite orbit and clock products, giving rise to estimates possibly affected by orbital and/or clock errors. In regard to SPB dissemination, the customary methods tacitly form linear combinations including extra-wide-lane, wide-lane as well as narrow-lane, which are not necessarily the best choice as far as their temporal stability is concerned. For these reasons, we derive three methods for estimating SPBs that are applicable, respectively, to scenarios with “insignificant orbital and clock errors”, with “significant clock errors” and with “significant orbital and clock errors”. For our derivation, undifferenced and uncombined observation equations are the point of departure, construction of full-rank functional model through rank deficiency elimination is the key issue, full exploitation of existing information is the main feature, adequate elimination of orbital or clock errors is the typical advantage. To optimize the efficiency of SPB dissemination, we “de-correlate” the uncombined SPB estimates by means of Z-transformation, so as to automatically search for a set of linear combinations that are the most suitable for being disseminated. The outcomes of relevance will enrich the theory and methods of SPB estimation, and provide support for working out a reasonable scheme for disseminating multi-frequency, multi-GNSS SPBs.

PPP-RTK是当今最前沿的GNSS精密定位技术，其应用和发展却受制于卫星相位偏差改正信息的准确性和有效性。针对卫星相位偏差估计，现有方法对精密卫星轨道和钟差产品较为依赖，其结果将可能受轨道或钟差误差影响；针对卫星相位偏差播发，现有方法默认形成（超）宽巷和窄巷等线性组合，但就时间稳定性而言，它们未必最适合被播发。为此，本项目提出分别适用于“轨道和钟差误差不显著”，“仅钟差误差显著”和“轨道和钟差误差均显著”情形下的三种卫星相位偏差估计方法：其出发点是非差非组合观测方程；其核心技术是通过消除秩亏建立满秩函数模型；其特色是最大程度地利用已有信息；其优点是可以有效克服轨道或钟差误差影响。为确保最优播发效率，提出借助整数变换技术，对非组合卫星相位偏差估值实施“降相关”，自动搜索出最适合播发的线性组合。研究成果将可丰富卫星相位偏差估计的理论和方法，并为制定多频多GNSS卫星相位偏差播发方案提供参考。

具备整周模糊度固定能力的精密单点定位（PPP-RTK）是卫星导航领域的前沿技术和研究热点。该技术的实现过程包括：1. 参考站网端数据处理，用以获取包含卫星相位偏差在内的一系列改正信息；2. 用户端实时高精度绝对定位，即联合改正信息和单台接收机观测数据，实时估计模糊度固定位置解。卫星相位偏差改正信息的准确性和播发效率直接决定了用户端模糊度固定的成功率和位置解的时效性。为此，本项目开展了两个方面的研究工作。首先，对现有卫星相位偏差估计方法进行了精化和改进：精化是指建立了顾及“卫星轨道信息已知”、“卫星轨道和钟差已知”和“卫星轨道和钟差未知”等三种不同约束条件下的卫星相位偏差估计方法；改进是指紧扣多频率、多系统的现实条件，将卫星相位偏差的估计方法由基于双频组合观测值拓展至基于多频非组合观测值。其次，对卫星相位偏差估值实施降相关，寻找不同观测频率（双频、多频）、不同导航系统（GPS/GALILEO/BDS）等观测条件下最稳定的线性组合，为制定合理的卫星相位偏差播发效率提供参考。本项目的研究成果包括：1. 发现了接收机相位偏差的变化规律、影响因素与建模方案，建立了顾及随机观测噪声、多路径效应和环境温度三种因素影响下的接收机相位偏差动态模型，显著提高了卫星相位偏差的估计精度、缩短了PPP-RTK用户模糊度首次固定的时间。2. 基于多频率非组合观测方程，推导了“站星几何构型无关”、“站星几何构型固定”和“站星几何构型与卫星钟差固定”三种模式下的满秩函数模型，实现了不同观测条件下的卫星相位偏差最优估计。3. 基于大陆构造环境监测网络数据，明确了各种模式下最适合被播发的线性组合以及各类线性组合的经验稳定时长；实验分析了中国区域各地静态、动态PPP-RTK的模糊度首次固定时间和定位精度等。本项目的研究成果丰富了全球导航卫星系统数据处理理论策略，解决了PPP-RTK技术推广和应用过程中亟需解决的如何准确估计卫星相位偏差、如何制定最优卫星相位偏差播发方案等科学与技术问题。