Extending Wide Area and Virtual Reference Station Networks Far Into the Sea With GPS Buoys

Oscar L. Colombo, Manuel Hernandez-Pajares, Miguel Juan and Jaume Sanz

Abstract:	We have studied the potential of using buoys with GPS receivers as floating network stations, to extend, far into the sea, the navigation services offered by land-based WAAS/EGNOS and Virtual Reference Station networks. In particular, we have investigated the feasibility of real-time resolution of carrier phase ambiguities with a roving receiver hundreds of kilometers away from shore. Central to that resolution, is the modeling of the ionosphere using data from both land- and buoy-based GPS receivers in the network, particularly in the presence of Traveling Ionospheric Disturbances (TID) and other perturbations, and of occasional interruptions in buoy receiver operation, with complete loss of lock lasting several minutes. Establishing precise kinematic location of the buoy quickly at start-up, and recovering it soon after an interruption in GPS reception, are essential to the use of buoys as effective aids to precise navigation. Ways of speeding up the real-time convergence of the buoy’s estimated position in such cases are discussed in this paper. In our preliminary tests, we have used 5-second GPS data from widely spaced NGS CORS stations, from days with low and quite high ionospheric activity. One of them, situated eastwards from all the others, was used in lieu of a buoy, and positioned kinematically relative to the “fixed” sites, while contributing data to precise, Virtual Reference Station ionospheric differential corrections, and to WAAS-type ionospheric models. Other receivers were kept in reserve, to be treated as user “rovers”, also positioned kinematically. We then considered the quality of the ionospheric corrections, from the point of view of fixing the “rover” ambiguities relative to the “master” station. The estimated rates of successful ambiguity resolution attempts are comparable to those for conventional, land based Virtual Reference Station and DGPS networks of smaller size. The quality of the corrections of the ionosphere derived from models obtained by computed tomography is adequate, in particular, for WAAS/.EGNOS-assisted navigation.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	560 - 572
Cite this article:	Colombo, Oscar L., Hernandez-Pajares, Manuel, Juan, Miguel, Sanz, Jaume, "Extending Wide Area and Virtual Reference Station Networks Far Into the Sea With GPS Buoys," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 560-572.
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