133: Resilient PNT by a combined GNSS/eLoran/INS approach for U-space applications

EC Regulation 2021/664 defines a minimum set of requirements for the Unmanned Aircraft Systems (UAS) operations in certain geographical zones, which is called U-space. U-space defines new services relying on a high level of digitalisation and automation, designed to provide access to airspace for large numbers of unmanned aircraft.

Emerging U‑space Beyond Visual Line of Sight (BVLOS) operations, e.g., infrastructure inspection, delivery services, search and rescue operations, etc. increasingly depend on trusted, high‑accuracy and resilient PNT, but GNSS-centric solutions remain vulnerable to interference, spoofing, jamming, multipath effects and PPP-convergence limitations. Galileo OSNMA provides authenticated navigation messages, Galileo HAS enables high‑accuracy positioning and eLoran offers a robust terrestrial timing layer, however, no integrated concept currently combines these elements into a unified architecture meeting U‑space integrity, continuity and availability requirements.

Note that NAVISP has funded projects for the development of compact H-field eLoran antennas and GNSS/eLoran integrated receivers, whose concept could be useful for this activity. 

The objective of this activity is to define a hybrid PNT concept that leverages Galileo signals authenticated by OSNMA, high‑accuracy corrections provided by HAS, a terrestrial timing layer from eLoran, a barometer for altitude estimation and Inertial Navigation Sensors (INS) to enhance PNT resilience for future U‑space applications.

The tasks to be performed shall include:

• The concept aims to illustrate how timing-aided hybridisation could accelerate PPP convergence, improve resilience to GNSS interference and spoofing, support GNSS-fault detection, and provide PNT-health indicators suitable for U-space functions such as Remote ID, Flight Authorisation and Geo-awareness. The focus is on outlining feasibility, potential performance benefits and operational relevance. The concept investigates a loosely coupled, timing-aided hybrid PNT stack integrating OSNMA, HAS, eLoran timing and INS to support resilient navigation in future U-space environments. 
• The concept also considers the research needs including authentication-aware integrity, GNSS/eLoran timing coherency validation, PPP convergence and re-convergence behaviour, data-driven eLoran analysis and the definition of KPIs and test methods for a hybrid-PNT performance assessment. An UAV-based hybrid-PNT demonstrator at conceptual level will serve as an illustrative TRL 4 pathway to explore feasibility and potential benefits. 

The approach considers eLoran compact H-field antennas or similar, a horizontal accuracy of 10m (vertical accuracy not being very important for eLoran time transfer, even though the inclusion of a barometer or similar for the altitude estimation is considered necessary). The technology development activity will be defined in compliance with the EU Regulation 2021/664 on U-space.

The main outputs of the activity will consist of:

• a conceptual framework for timing-aided hybrid PNT, including architectural principles, integrity and timing coherency mechanisms, potential benefits for U-space services, and guidance for future research; 
• outline of performance-relevant KPIs, identification of reference datasets and test methodologies needed for evaluating hybrid PNT, and definition how to support future Specific Operations Risk Assessment (SORA)-considerations and Remote ID records in evaluation contexts;
• considerations to inform future higher-TRL development of resilient hybrid-PNT solutions. 

It is noted that Italy expressed their opt-out for this activity (EL1-133).