基于单频BDS非差非组合网解模式的电离层TEC计算方法研究

The computational quality of TEC information is the core basic to ensure the accuracy of modeling GNSS ionosphere. Currently, the single-frequency undifferenced and uncombined PPP technology has attracted more and more attention in the field of GNSS ionospheric research, due to its advantages of high accuracy and low cost. Aiming at the problem of ionospheric TEC computing quality constrained by failed integer ambiguity resolution and low model strength in PPP processing, this project will deeply study how to integrate the advantages of single-frequency undifferenced and uncombined model and multi-station BDS network technology, by doing this to improve the quality of ionospheric modeling and reduce its application cost. Our project will focus on: 1) accurately parameterize the ISTB of inter-type deviation of BDS satellites, and construct a theoretical rigorous single-frequency BDS undifferenced and uncombined network model to estimate ionospheric TEC; 2) develop the method of extracting ionosphere in single-frequency BDS undifferenced and uncombined network mode；3) design an adaptive transformation algorithm which is suitable for the undifferenced and uncombined network mode, by doing this to reduce the instability of ionospheric TEC calculation whic is caused by the change of reference stars. We expected that our research will improve the quality of ionospheric TEC calculation and enrich the theory of GNSS data processing, and also provide reference for researching ionospheric TEC model by using single-frequency BDS/multi-GNSS network solutions.

GNSS斜距电离层TEC信息的计算质量是保障电离层精确建模的核心基础信息。近年发展的单频非差非组合PPP斜距电离层TEC提取方法因具有精度高、成本低等优势，逐渐为GNSS电离层研究领域所关注。本项目将针对PPP函数模型强度低、整数模糊度无法固定等导致的电离层TEC计算质量受限问题，深入研究如何高效融合单频非差非组合与多站BDS网解技术优势，整体提升电离层建模质量、降低其应用成本。重点研究：1）准确参数化BDS卫星类型间偏差ISTB，构建理论严密的单频BDS非差非组合网解模型；2）发展单频BDS非差非组合网解模式下的斜距电离层TEC精密提取方法；3）设计适用于非差非组合网解模式的参考星自适应变换算法，力求降低参考星变化引发的电离层TEC计算的不稳定性。预期研究成果有望提高电离层TEC解算及建模质量，丰富GNSS数据处理理论，为开展单频BDS/多GNSS网解电离层TEC建模研究与应用提供参考。

本项目深入研究了基于北斗卫星导航系统的电离层精密提取方法，基于此方法对我国及全球电离层异常现象的研究做了详细的分析，同时联合威海天文观测站和GNSS地面站观测网重点对电离层扰动事件进行大范围长期连续观测，研究电离层不均匀体结构的形成机制，同时，本项目以现代信息化手段为抓手，研究了GNSS接收机的硬件设计问题、THZ及机器学习等相关技术，为未来交叉学科的综合应用做了探索。