title: Global Ionospheric Modelling using Multi-GNSS: BeiDou, Galileo, GLONASS and GPS.
abstract: The emergence of China's Beidou, Europe's Galileo and Russia's GLONASS satellites has multiplied the number of ionospheric piercing points (IPP) offered by GPS alone. This provides great opportunities for deriving precise global ionospheric maps (GIMs) with high resolution to improve positioning accuracy and ionospheric monitoring capabilities. In this paper, the GIM is developed based on multi-GNSS (GPS, GLONASS, BeiDou and Galileo) observations in the current multi-constellation condition. The performance and contribution of multi-GNSS for ionospheric modelling are carefully analysed and evaluated. Multi-GNSS observations of over 300 stations from the Multi-GNSS Experiment (MGEX) and International GNSS Service (IGS) networks for two months are processed. The results show that the multi-GNSS GIM products are better than those of GIM products based on GPS-only. Differential code biases (DCB) are by-products of the multi-GNSS ionosphere modelling, the corresponding standard deviations (STDs) are 0.06 ns, 0.10 ns, 0.18 ns and 0.15 ns for GPS, GLONASS, BeiDou and Galileo, respectively in satellite, and the STDs for the receiver are approximately 0.2~0.4 ns. The single-frequency precise point positioning (SF-PPP) results indicate that the ionospheric modelling accuracy of the proposed method based on multi-GNSS observations is better than that of the current dual-system GIM in specific areas.
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, 430079, Wuhan, Hubei, China.|Key Laboratory of Precise Engineering and Industry Surveying of National Administration of Surveying, Mapping and Geoinformation, 129 Luoyu Road, 430079, Wuhan, Hubei, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Ren
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, 430079, Wuhan, Hubei, China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, 430079, Wuhan, Hubei, China.
authors.forename: Weiliang
authors.initials: W
authors.lastname: Xie
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, 430079, Wuhan, Hubei, China.
authors.forename: Keke
authors.initials: K
authors.lastname: Zhang
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, 430079, Wuhan, Hubei, China.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: German Research Centre for Geosciences (GFZ), Telegrafenberg, 14473 Potsdam, Germany.
authors.forename: Xingxing
authors.initials: X
authors.lastname: Li