Assessment of Methods to Trigger Transition Between Multiple SBAS

J. Dennis, M. Hemstad

Abstract:	This paper provides an assessment of various parameters that might be used by DFMC SBAS airborne equipment to trigger transition from one SBAS to another. Currently only the approach phase of flight has requirements related to SBAS selection. There are no airborne equipment standards related to SBAS selection in the en route or terminal phases of flight. Current equipment transitions are based on unpublished manufacturer algorithms. The reported response of SBAS transitions and the pending introduction of new SBAS systems suggest a need for improvement of the transition methodology. SBAS has the potential to provide global capability for en route, terminal and precision approach operations. Unlike most ground-based navigation systems, DFMC SBAS can provide valid navigation in regions with no supported ground infrastructure. The extension to DFMC can increase the extent of service availability from existing SBAS, resulting in larger regions of overlapping SBAS service availability. Without any new SBAS selection requirements in the standards, this may result in equipment operating in the same airspace in the en route or terminal mode using different SBAS. For some SBAS, the equipment might be relatively far away from the reference network providing the augmentation. However, SBAS users are likely to achieve better performance when using corrections from an SBAS with nearby reference stations. Selection methods might want to leverage this measurable performance difference. This paper assesses SBAS selection and transition regions based on broadcast integrity parameters. It assesses parameters expected to be available to DFMC SBAS avionics from five operating SBAS systems implementing dual-frequency augmentation service. The assessment uses a simulation tool to generate the integrity parameters. Results demonstrate a reasonable capability to select the SBAS using the broadcast data. Results include an assessment of either a single core constellation (Global Positioning System (GPS)) or two core constellations, (GPS and Galileo); with the expectation that these results will be applicable to SBAS that also augment other core constellations such as Global Orbiting Navigation Satellite System (GLONASS) or BeiDou.
Published in:	Proceedings of the 2014 International Technical Meeting of The Institute of Navigation January 27 - 29, 2014 Catamaran Resort Hotel San Diego, California
Pages:	201 - 211
Cite this article:	Dennis, J., Hemstad, M., "Assessment of Methods to Trigger Transition Between Multiple SBAS," Proceedings of the 2014 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2014, pp. 201-211.
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