단기선 환경에서 측정 도메인 모니터를 활용하는 CDGNSS 시스템의 보호수준 산출

Abstract

Swarm operations for unmanned vehicles are expanding across reconnaissance, logistics, and defense applications. Missions with tight inter-vehicle spacing—such as aerial refueling and close-formation flight—require centimeter-level relative positioning and navigation integrity. This paper presents a protection level (PL) computation method for carrier phase differential GNSS (CDGNSS) that operates with measurement-domain monitors. We derive the biases in the Kalman filter estimates caused by undetected faults with consideration of the recursive nature of the filters. The impacts of these biases on fixed-baseline solutions and ambiguity resolution are separately derived under the worst-case scenario. These impacts are then combined to compute the PL. The performance of the proposed method is assessed through simulations assuming the use of an ephemeris monitor. The computed PLs are compared with PLs computed using a Solution Separation (SS)-based method. The obtained results show that, for short baselines, the proposed method yields smaller PLs and a lower computational burden by avoiding parallel multi-subset filtering. Sensitivity analyses across inter-vehicle separations indicate that the performance degrades with increasing baseline distance, whereas the benefits are strongest at short separations. Given these characteristics the approach is well-suited to tightly spaced multi-vehicle operations.