UKSBAS Testbed: A Comprehensive Performance Review over two Years of Operations

Javier González, Fernando Bravo, Madeleine Easom, Juan R. Campano, Ignacio Sainz, David Hill, and George Newton

Abstract:	Current Satellite-Based Augmentation Systems (SBASs) improve the positioning accuracy and integrity of GPS satellites and provide safe civil aviation navigation services for En-route to LPV-200 precision approaches over specific regions. SBAS systems have already been commissioned and operate in the case of United States (WAAS), the European Union (EGNOS), India (GAGAN), Japan (MSAS) and South Korea (KASS), while advances are being made in other SBAS systems around the world such as SouthPAN, BDSBAS, SCDM, ASECNA and UKSBAS. Currently, the development of operational SBAS systems is in a moment of transition. This boost is due to both the extension of traditional L1 SBAS services to new regional areas and the implementation of new L1 SBAS that involve service areas overlapping with existing services. In addition, important improvement is expected through the introduction of Dual Frequency Multi-constellation (DFMC) services. DFMC SBAS allows the joint use of additional core constellations such as Galileo and the bi-frequency solution (L1-L5 and E1-E5a) that removes a significant part of the ionospheric error through the iono-free combination. In the present circumstances, the UKSBAS testbed is a demonstration and feasibility project delivering a new Signalin-Space (SiS) L1 SBAS signal that has been live since May 2022 over the UK using a geostationary (GEO) satellite and L1 SBAS and DFMC SBAS services via the Internet. These activities have been carried out in the framework of ESA’s Navigation Innovation Support Programme (NAVISP) sponsored by the UK’s HMG with the participation of the Department for Transport and the UK Space Agency. The testbed’s signal broadcast uses Viasat's / Inmarsat’s 3F5 geostationary (GEO) satellite in orbit and Goonhilly Earth Station are uplinking the L1 SBAS message corrections and integrity information over PRN 158. The core L1 and DFMC SBAS Message generation is carried out by GMV’s magicSBAS software and is also delivered over the Internet using SisNet technology. The ground segment is composed of several Continuously Operating Reference Stations (CORS) selected from Ordnance Survey’s and IGS’s station network. The system is continuously monitored and surveyed through GMV’s magicMonitor front-end webpage. The objective of this paper is to provide a description of the UKSBAS testbed architecture from the point of view of the infrastructure involved in the generation, broadcast, monitoring, and analysis of the SBAS messages and an assessment of the performances achieved at system level during the last two years of operations. This assessment will comprise of the following: - Performance analysis results from the signal broadcast, SBAS L1 and SBAS DFMC separately, including service availability for aviation-related service levels (i.e.: APV-I, LPV-200) and characterization of Protection Levels (PL) and Position Errors (PE) statistics over the service area and in a network of receivers. - Accuracy statistics provided by SBAS L1 and SBAS DFMC differential corrections compared to precise postprocessed SP3 and IONEX reference data. At satellite level, advanced statistical characterization of the satellite orbit and clock errors is assessed through relevant metrics such as the Satellite Residual Error (SRE), its projection onto the Worst User Location (WUL, SREW), and the comparison against the related integrity overbounding parameter, the User Differential Range Error (UDRE). At Ionospheric level, the Grid Ionospheric Vertical Delay error (GIVDe) and Grid Ionospheric Vertical Error (GIVE) are also studied with historical data.
Published in:	Proceedings of the 37th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2024) September 16 - 20, 2024 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	451 - 464
Cite this article:	González, Javier, Bravo, Fernando, Easom, Madeleine, Campano, Juan R., Sainz, Ignacio, Hill, David, Newton, George, "UKSBAS Testbed: A Comprehensive Performance Review over two Years of Operations," Proceedings of the 37th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2024), Baltimore, Maryland, September 2024, pp. 451-464. https://doi.org/10.33012/2024.19914
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