GNSS performance monitoring and augmentation for Advanced Air Mobility

Navigation systems that are adequate for Advanced Air Mobility (AAM) safety-critical applications must achieve levels of robustness, flexibility and reliability that are unprecedented in the realm of aviation for civil use. With the increase in the accessibility of new airspaces such as urban environments, the performance (i.e. accuracy, integrity, availability and continuity) of the navigation system has become of paramount importance. Global Navigation Satellite Systems (GNSS) are, thus far, among the most promising in meeting the performance requirements of those applications but not without sufficient operation-based augmentation. An Aircraft-Based Augmentation System (ABAS) allows for performance monitoring without reliance on external equipment. This paper proposes an evolution of the ABAS concept with deterministic predictive integrity monitoring capabilities suitable for highly challenged AAM applications. Raytracing-based models for antenna masking and multipath, which are highly dependent on the topographical surroundings, vehicle dynamics and airframe shape are integrated in the augmentation system. A simulation-based system verification is included assessing the achievable protection levels in a representative urban environment with flights below and above skyline as well as the feasibility of the system’s implementation. Results show promising integrity monitoring performance with high rates of detection exceeding 90% and low rates of false alarms below 5% for horizontal positioning. Best performance is observed at an operating altitude close to the average building height in the studied region (75 m height) with a 100% detection rate and 0% false alarm rate. The system showed great potential for its implementation and usage for AAM flight path and mission planning. Moreover, findings support the identification of a PBN requirement framework that would support high-integrity flight operations in future urban and suburban environments.