With support from the European Space Agency (ESA), UK-based GMV NSL Ltd. has completed the RIGOUR (‘Real-time integrity for GNSS using opportunistic receivers) project, demonstrating how large volumes of measurements from everyday GNSS devices could support future integrity monitoring concepts.
Conventional GNSS integrity architectures rely primarily on dedicated reference station networks to monitor satellite performance and detect anomalies. RIGOUR used opportunistic measurements collected from large numbers of GNSS receivers found in standard smartphones or vehicle navigation systems.
Although mass-market receivers provide noisier measurements than professional reference stations, the aggregation of very large datasets can compensate for reduced measurement quality. Statistically robust information about satellite behavior and signal conditions can be extracted when using observations from thousands of users in real time.
The project team developed a dedicated simulation platform and a GNSS integrity processor (GIP) capable of combining measurements from large numbers of distributed users. The RIGOUR demonstrator simulated 10,000 receivers operating in rural, urban and dense local environments, representing both mass-market and high-end devices with varying sampling rates and signal configurations.
The results are in
RIGOUR assessed two complementary GNSS integrity services. The first, satellite (global) integrity, aggregates measurements from geographically distributed user receivers to detect satellite faults and generate protection parameters, producing indicators such as sigma user differential range error (UDRE) values used to compute positioning protection levels.
The second concept, local integrity, exploits dense clusters of GNSS users in areas such as urban streets to identify environmental effects including multipath, blockage and interference. By looking at the errors measured by many nearby GNSS users, the system can detect local signal problems and adjust the safety margin for that area, without impacting users elsewhere.
Large-scale simulations under nominal and degraded conditions showed the processor could detect moderate-to-large satellite anomalies and improve observability through widely distributed user measurements. Detectability of certain faults depended on the availability of low-variance measurements, suggesting that measurements from rural environments can significantly enhance monitoring performance. Meanwhile, the local integrity concept demonstrated benefits in dense environments, although additional modeling and sensor-fusion approaches may be needed to address severe urban effects such as non-line-of-sight signals.
RIGOUR demonstrates that as the number of connected navigation devices continues to grow, big-data approaches could complement existing infrastructure and support new integrity services for applications ranging from transport to autonomous systems.
This project was funded under ESA’s NAVISP program, aimed at strengthening the European PNT industry.
