Session D3: Precise Positioning and its Integrity: Architecture and Algorithm Design

Integrity Monitoring of SSR Services for a Dual Automotive and Rail Augmentation Network
Mauro Cardone, ASI - Italian Space Agency; Alessandro Neri, Alessia Vennarini, Arianna Persia, Valeria Ioannucci, and Francesco Rispoli, Radiolabs
Location: Windsong 5-6
Date/Time: Thursday, Sep. 17, 9:20 a.m.

High-accuracy GNSS augmentation with safety-grade integrity is a key enabler for automated rail and automotive positioning, where conventional commercial correction services often provide accuracy and availability but limited support for integrity monitoring. This paper presents the integrity monitoring concept adopted for the Italian RAN (Rete di Augmentation Nazionale), a national augmentation infrastructure designed to provide RTK, PPP, and PPP-RTK services through a common, scalable network architecture serving both railway and road applications. The proposed approach extends previous Augmentation and Integrity Monitoring concepts developed for Observation Space Representation (OSR) products to State Space Representation (SSR) services, with emphasis on compliance with emerging high-integrity GNSS standardization frameworks. RAN combines EGNOS, Galileo HAS, and a dense second-tier network of Reference and Integrity Monitoring stations to generate local corrections, integrity data, and Quality of Service indicators. The paper describes the multi-tier system architecture, the SSR state components, and the processing chain used to estimate satellite, atmospheric, receiver, and ambiguity-related correction terms. A central contribution is the network-level Fault Detection and Exclusion strategy, based on residual monitoring, signal combinations, parity-space tests, Mahalanobis statistics, and independent validation stations not used in correction generation. These mechanisms support the detection and exclusion of faulty satellites, degraded reference stations, and anomalous atmospheric or correction products before dissemination to users. The paper also discusses how On Board Units (OBUs) exploit RAN integrity parameters to compute accuracy and integrity key performance indicators, including protection levels based on overbounding models of SSR correction errors. Finally, a fault-tree analysis of the PPP-RTK service illustrates the allocation of integrity risk across augmentation, reference station, control-center, communication, and external-provider domains. The resulting framework provides a unified integrity-aware augmentation approach for multimodal automated transport and is extensible to future LEO-PNT services.