Assessment on the Interoperability of SBAS and GRAS

Jyh-Ching Juang, Shau-Shiun Jan and Yung-Fu Tsai

Abstract:	Many space-based augmentation systems have been developed recently to augment GNSS (global navigation satellite system) services. A SBAS (space-based augmentation system) employs a set of reference stations to continuously collecting GNSS signals, master stations to determine the correction and integrity information, and geostationary satellites to broadcast correction, integrity, and ranging messages for navigation augmentation. As an alternative to SBAS, the GRAS (ground-based regional augmentation system) employs similar reference and monitor stations with the exception that ground-based VHF stations are used to broadcast messages. The GRAS is considered beneficial when the satellite is not available or when sovereignty control is needed. In the paper, issues on the interoperability and integration of SBAS and GRAS will be investigated, using Taiwan (Taipei FIR) as an example. Indeed, for Taipei FIR, a unique challenge in meeting the required accuracy, integrity, and availability is due to the rather sparsely distributed reference stations used in the SBAS, say, MSAS. As such, the service availability and coverage may not meet the required level. The problem is further aggravated as Taipei FIR being located in a low geomagnetic latitude region is subject to severe to ionospheric effects and scintillations. On the other hand, a set of continuously operating reference stations have been installed in the island and can be used to provide augmentation service. Analyses pertaining to service volume modeling, quality, and availability are performed to seek an interoperability of the two systems. A GRAS type concept, GRAST, is proposed to address the need of assured navigation quality, interoperability with SBAS, and sovereignty control.
Published in:	Proceedings of the 2005 National Technical Meeting of The Institute of Navigation January 24 - 26, 2005 The Catamaran Resort Hotel San Diego, CA
Pages:	537 - 543
Cite this article:	Juang, Jyh-Ching, Jan, Shau-Shiun, Tsai, Yung-Fu, "Assessment on the Interoperability of SBAS and GRAS," Proceedings of the 2005 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2005, pp. 537-543.
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