Integration of Galileo High Accuracy Service within ARAIM for enhanced navigation performance

Abstract

Currently, Advanced Receiver Autonomous Integrity Monitoring (ARAIM) only plans to support air navigation up to LPV-200, mainly due to limitations imposed by the Signal-In-Space (SIS) errors. This work proposes a novel approach where the Galileo High Accuracy Service (HAS) is integrated within ARAIM, analyzing the potential benefits of using a more precise continuity Signal-In-Space error model. First, a sensitivity analysis is performed on ARAIM world-wide availability with respect to the main Integrity Support Message (ISM) parameters and HAS corrections accuracy. Secondly, using precise products from the International GNSS Service (IGS) as a reference, orbit and clock errors of broadcast and HAS-corrected ephemeris are characterized for GPS and Galileo constellations, obtaining an independent analysis of the expected performance for HAS in terms of ranging errors. From this analysis, a continuity error model is derived.

Finally, the proposed algorithm is tested with observation data from an experimental flight campaign, using ionospheric-free dual-frequency dual-constellation observations. The positioning error is analyzed as well as the key performance indicators of ARAIM, such as protection levels improvements. Results suggest that a reduction of vertical and horizontal protection levels between 5% and 10% can be expected.

Additionally, a reduction of unavailability for LPV-200 navigation requirements of more than 50% was found for the validation dataset. This indicates that the integration of Galileo HAS with ARAIM could be able to deliver an enhancement of performance for operations with strict requirements such as urban air mobility or civil aviation.