Integrity Support Messages Format for GNSS Precise Products: Design and Evaluation

Zhen Lyu, Zishen Li, Ningbo Wang

Peer Reviewed

Abstract:	Integrity is a cornerstone of safety assurance across aviation, autonomous, and maritime applications. Within the Global Navigation Satellite System (GNSS), the International GNSS Service has long provided standardized precise products such as satellite orbits and clocks, yet none contain explicit integrity information. To address the absence of standardized integrity representation for high-precision GNSS, this study proposes the first Integrity Support Message (ISM) format designed specifically for precise orbit and clock products. The proposed ISM introduces two types of indicators: Quality Indicator (QI) and Health Indicator (HI). QIs are derived from multi-GNSS Precise Point Positioning with Ambiguity Resolution (PPP-AR) residuals using a Gaussian bounding process that provides satellite- and frequency-specific statistical parameters. HIs are generated through threshold-based fault detection under user integrity risk requirements, converting residual alarms into binary satellite health statuses, with zero indicating healthy and one indicating unhealthy. A structured ISM file format is developed following International GNSS Service naming conventions and a Solution Independent Exchange (SINEX) style header to ensure interoperability. QI files, typically updated monthly, are consolidated by constellation, while HI files are updated every 30 seconds to reflect satellite status in real time. Validation using ten precise products from CODE, CNES, GFZ, and WHU across GPS, Galileo, and BDS-3 demonstrates systematic differences in statistical properties and fault detection performance. The results confirm the feasibility of ISM as a unified integrity layer for precise products, enabling the transition from accuracy centric to reliability-centric positioning and laying the foundation for future standardization of GNSS integrity products.
Published in:	Proceedings of the 2026 International Technical Meeting of The Institute of Navigation January 26 - 29, 2026 Hyatt Regency Orange County Anaheim, California
Pages:	312 - 324
Cite this article:	Lyu, Zhen, Li, Zishen, Wang, Ningbo, "Integrity Support Messages Format for GNSS Precise Products: Design and Evaluation," Proceedings of the 2026 International Technical Meeting of The Institute of Navigation, Anaheim, California, January 2026, pp. 312-324. https://doi.org/10.33012/2026.20496
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