Preliminary Study on Network Ionospheric Monitoring for DFMC GBAS Using Collaborative Airborne Receivers

Xuedong Huang, Kun Fang, Wang Li, Zhipeng Wang, Yanbo Zhu

Abstract:	To ensure the integrity of dual-frequency multi-constellation (DFMC) Ground-Based Augmentation Systems (GBAS) under disturbed ionospheric conditions, accurate real-time monitoring of ionospheric gradients is essential. Traditional GBAS threat models are derived from global or regional statistical analysis and tend to be overly conservative, resulting in reduced service availability. With the emergence of GAST E, airborne receivers are now capable of collecting dual-frequency GNSS observations, enabling collaborative ionospheric monitoring near airports. This study proposes a framework that utilizes aircraft as distributed sensors to estimate localized ionospheric gradients in real time, supporting the development of adaptive threat models. The proposed method relies on Code-Carrier Divergence (CCD) monitoring to identify ionospheric anomalies and employs a weighted least squares plane fitting approach to estimate slant ionospheric gradients based on delay differences across multiple airborne receivers. The accuracy of this method is enhanced by dynamic error modeling of carrier-smoothed pseudorange (P4) observations, incorporating time-dependent noise variance derived from smoothing filter theory. To evaluate system performance, a realistic flight scenario is simulated using the Spirent GSS9000 GNSS simulator. Eight aircraft follow a “Touch and Go” procedure at Beijing Capital Airport, with synthetic ionospheric storm profiles introduced into the measurement domain. Three distinct ionospheric threat scenarios are tested, varying in gradient magnitude and propagation direction. Results demonstrate that the proposed method significantly outperforms traditional station-pair techniques in both stability and accuracy, particularly under large gradient conditions.
Published in:	Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025) September 8 - 12, 2025 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	224 - 238
Cite this article:	Huang, Xuedong, Fang, Kun, Li, Wang, Wang, Zhipeng, Zhu, Yanbo, "Preliminary Study on Network Ionospheric Monitoring for DFMC GBAS Using Collaborative Airborne Receivers," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 224-238. https://doi.org/10.33012/2025.20270
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