近年来，以GPS、GLONASS、BDS和GALILEO等系统为代表的GNSS在不断现代化与快速建设发展中。多模多频GNSS融合数据处理成为未来的发展趋势，并将进一步提高导航定位服务的精度、可靠性和可用性。在此背景下，结合行业内日益增长的对实时高精度定位、导航、授时以及大气探测等应用领域的需求，本项目拟针对多模多频实时非组合精密单点定位（PPP）模型算法及其电离层应用开展深入研究，包括：（1）构建满秩、灵活、后向兼容的多模（四系统）多频（三频及以上）非组合PPP函数模型；（2）研究稳健的、基于数据流的多模三频非组合PPP滤波算法及其高效的实时多测站处理方案；（3）基于实时多模三频非组合PPP提取的高精度电离层斜延迟信息，开展实时电离层VTEC建模算法研究。本项目研究成果将丰富和发展多模精密定位及相关应用的模型与算法，并为解决部分关键问题提供新的思路和方法，具有显著的研究意义和应用前景。

In recent years，the Global Navigation Satellite System (GNSS), which is represented by GPS, GLONASS, BDS and GALILEO, has been experiencing continuous modernization and rapid construction and development. Joint processing with multi-GNSS and multi-frequency data has become the future trend and will further improve the precision, reliability and availability of positioning and navigation services. Under this background, and combined with the increasing application demand for real-time high-precision positioning, navigation, timing and remote sensing the earth’s atmosphere in GNSS community, this project is aiming to carry out studies on the models and algorithms of raw observation based real-time multi-GNSS triple-frequency Precise Point Positioning (PPP) and its ionospheric applications, including: (1) construct a full-rank, flexible and backward compatible function model for raw observation based multi-GNSS (quad-system) and multi-frequency (triple or more) PPP; (2) study robust and stream-based algorithms for real-time filtering for multi-GNSS triple-frequency PPP and design an efficient solution for real-time multi-station processing; (3) with the real-time high-precision slant ionospheric delays retrieved from raw observation based multi-GNSS triple-frequency PPP, study the algorithms for real-time ionospheric VTEC modeling. This research has significant value and application prospect, for the fact that the related achievements will enrich and develop the models and algorithms of multi-GNSS and multi-frequency precise positioning and its related applications, which also provide new ideas and methods to solve some of the key problems.