Ephemeris monitor with ambiguity resolution for CAT II/III GBAS
- PDF / 2,326,976 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 54 Downloads / 192 Views
ORIGINAL ARTICLE
Ephemeris monitor with ambiguity resolution for CAT II/III GBAS Yiping Jiang1 Received: 12 March 2020 / Accepted: 31 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In safety-critical applications, such as the Ground-Based Augmentation System for precision approaches in civil aviation, it is important to safeguard users under the case of ephemeris failures. For CAT II/III approaches, different ephemeris monitors with approaches for ambiguity resolution are proposed with the double differenced carrier phase as the test statistics. The continuity risks introduced by the ambiguity resolution are addressed by deriving the required averaging time for new, acquired, and re-acquired satellites. Since the ephemeris fault is closely related with the baseline length between ground stations, the minimum baseline length is derived to meet the probability of missed detection region. Current methods are compared with both the averaging time and the ground baseline length. It is demonstrated that a combination of two methods is able to achieve the best performance with 94 averaging epochs and 218 m ground baseline length. Keywords GNSS · GBAS · Integrity monitor · Ephemeris monitor
Introduction The Ground-Based Augmentation System (GBAS) is used for precision approaches in civil aviation to improve both the accuracy and integrity of the Global Navigation Satellite System (GNSS) (Annex-10 2018). With accuracy improved by a local area differential positioning scheme between the ground and airborne receivers, how to guarantee the safety of aviation users within the required integrity level is a more challenging task. Integrity monitoring is implemented in airborne and ground subsystems for incidents that may result in large position errors. Failure of ranging source failure is one of the causes. Five types of threats are characterized in GBAS, including ionospheric anomaly, code-carrier divergence, signal deformation, satellite clock, and ephemeris failure (Brenner and Liu 2010; Jiang et al. 2017). It is within the responsibility of the ground subsystem to detect the ranging faults and remove the satellite before it is incorporated in the airborne solution. In the early history of GPS, the ephemeris error greater than 50 m has occurred on 24 occasions. A more recent case was observed on GPS SV54 with errors larger than * Yiping Jiang [email protected] 1
The Hong Kong Polytechnic University, Hong Kong, SAR, China
350 m in 2014 (Gratton et al. 2007). In GBAS, the ephemeris threat occurs when the broadcast ephemeris parameters yield excessive satellite position errors perpendicular to the ground subsystem’s line of sight (LOS) to the satellite (SARPs 2009; Pervan and Chan 2003). It has been proved that only satellite position errors perpendicular to LOS contributes to the differential range error (Matsumoto et al. 1999). The GBAS ephemeris threat is categorized as type A and type B threats, where the type A threat involves a satellite maneuver and type B does not. Typ
Data Loading...
