Accessing and Processing Real-Time GPS Corrections for Precise Point Positioning … Some User Considerations

P. Collins, Y. Gao, F. Lahaye, P. Héroux, K. MacLeod and K. Chen

Abstract:	Natural Resources Canada makes its GPS Corrections (GPS·C) available in real-time through the Canada-wide Differential GPS Service. These corrections have also recently become available over the Internet using prototype UDP and TCP servers. The latter uses the NTRIP model of data transfer to allow, in part, for the creation of Virtual Reference Stations and the production of RTCM-SC104 local-area corrections for Differential GPS. In addition, both servers provide high-precision wide-area corrections in a modified RTCA-SC159 format to provide the necessary precision to eventually realize real-time Precise Point Positioning (PPP) to the subdecimetre level. Obtaining the highest possible accuracy from GPS corrections requires an awareness of the clock reference, or datum, to which they refer. The pseudorange measurements selected for the correction computation determine the clock reference for those corrections. The GPS·C corrections are currently referenced to the C/A (C1) and P2´ (C1+P2-P1) pseudorange observables and users must match these to achieve the best possible accuracy. Failure to do so can degrade positioning precision by up to a factor of three or more.
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:	1483 - 1491
Cite this article:	Collins, P., Gao, Y., Lahaye, F., Héroux, P., MacLeod, K., Chen, K., "Accessing and Processing Real-Time GPS Corrections for Precise Point Positioning … Some User Considerations," 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. 1483-1491.
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