Improving DFMC SBAS Performance by Integrating L1 SBAS Ionospheric Corrections with an Ionosphere-Weighted Model

Jina Lee, Yongrae Jo, Byungwoon Park, Donguk Kim, Cheolsoon Lim

Abstract:	The satellite-based augmentation system (SBAS) provides precise positioning services and high reliability by broadcasting correction and integrity to users via geostationary (GEO) satellites. The current positioning model for dual-frequency multiconstellation (DFMC) SBAS effectively eliminates the first-order term of ionospheric delay error through an ionosphere-free (IF) linear combination of L1 and L5 dual-frequency measurements. However, this IF model has the disadvantages of halving the number of available measurements, which reduces the redundancy of the positioning model, and amplifying measurement noise by a factor of approximately 2.59 (Park et al., 2017). Furthermore, the limited availability of GPS L5 satellites weakens the positioning geometry, leading to high position dilution of precision (PDOP). To overcome these limitations, this study proposes a new approach based on an ionosphere-float model, which replaces the conventional DFMC SBAS IF model and directly estimates the ionospheric delay as a state variable. The core of this new method involves two key components: 1) constructing an ionosphere-weighted (IW) model by utilizing legacy L1 SBAS ionospheric corrections as pseudo-observables, and 2) integrating L1-only single-frequency satellites, supported by L1 SBAS, with the existing L1/L5 dual-frequency satellites. To validate the performance of the proposed method, a comparative analysis was conducted against the European Geostationary Navigation Overlay Service (EGNOS) DFMC. The experiment utilized both GPS and Galileo constellations as serviced by EGNOS. For this experiment, we calculated the positioning errors and protection levels to evaluate the performance enhancements of the proposed approach.
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:	122 - 131
Cite this article:	Lee, Jina, Jo, Yongrae, Park, Byungwoon, Kim, Donguk, Lim, Cheolsoon, "Improving DFMC SBAS Performance by Integrating L1 SBAS Ionospheric Corrections with an Ionosphere-Weighted Model," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 122-131. https://doi.org/10.33012/2025.20263
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