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Session C1: Aviation Applications of GNSS

Determining the Minimum Lateral Separation Distance for UAM Using ADS-B Information
Junsoo Kim, Gihun Nam, Jiyun Lee, Korea Advanced Institute of Science and Technology; Dongchan Min, Sam Pullen, Stanford University
Location: Prince Jonah Room
Date/Time: Tuesday, Apr. 14, 11:17 a.m.

Urban air mobility (UAM) is expected to increase traffic density in constrained low-altitude airspace, thereby increasing the risk of mid-air collisions and emphasizing the need for safe yet efficient separation management. Conventional aviation separation standards are too large to be directly applied to UAM without severely reducing airspace efficiency. Our prior research introduced a safety risk assessment (SRA)-based methodology for determining the minimum separation distance (MSD) for UAM tactical deconfliction. However, the earlier framework relied on a generic surrogate detection model and was limited to nominal operation. This study extends the framework by introducing an Automatic Dependent Surveillance-Broadcast (ADSB)-based representation of tactical deconfliction and by explicitly accounting for identified failure conditions in both the navigation system and the detection system. In the proposed approach, ADS-B integrity parameters, including the navigation integrity category (NIC), source integrity level (SIL), and source design assurance (SDA), are used to model traffic-state uncertainty, detection uncertainty, and ADS-B failure probability in a direct and traceable manner. Navigation-system failure conditions are represented as biases in the ownship total system error (TSE), while ADS-B failure conditions are modeled by loss of detection capability. A case study was conducted for a UAM system equipped with a GNSS/INS-integrated extended Kalman filter navigation system and an ADS-B-based detection system. The proposed methodology was used to compute the MSD and to analyze its sensitivity to ADS-B integrity parameters and ownship navigation system configurations. The results show that improving ADS-B integrity can substantially reduce the required separation distance. In particular, when NIC is improved from 8 to 9 and SDA is improved from 2 to 3, the final MSD decreases from 128 m to 88 m, achieving up to a 31% reduction. In addition, among the ownship navigation configurations considered, the dual-frequency multi-constellation configuration yields the smallest MSD, indicating that it is the most effective for reducing separation requirements while maintaining the required level of safety.

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