Dual-frequency GPS Precise Point Positioning with WADGPS Corrections

Hyunho Rho and Richard B. Langley

Abstract:	A number of wide area differential GPS (WADGPS) services (e.g., WAAS, EGNOS, and CDGPS - the Canada-wide Differential GPS Service) are now in operation and more are planned for the future. These free services will enhance the availability of real-time DGPS corrections across countries and continents by providing a quality geo-referencing capability especially for single frequency L1 GPS users. However, the satellite orbit and clock WADGPS corrections can also be used to improve the GPS positioning accuracy for dual-frequency users. The goal of the research described in this paper is the design of a GPS dual-frequency data processing technique capable of producing high-accuracy positioning results with WADGPS corrections. In this paper, we have designed the forward carrier-phase smoothing technique in the measurement domain as an approach for implementing dual-frequency precise point positioning using WADGPS corrections. Results determined via developed software indicate that a few decimeter-level positioning accuracy is attainable at the 2D r.m.s. For these results, we didn’t take into account the phase wind-up due to relative rotation of the satellite and receiver antennas, nor site displacement effects due to solid earth tides and ocean loading. To account for the satellite clock referencing issue, the effects of the satellite instrumental biases have been precisely investigated and the observation equations for the different observables assuming the source of corrections is WADGPS have been developed. With the developed observation model, we found about a 75 cm level of improvement in the horizontal position fixes and improvements of about factor of 2 in the vertical position component when the instrumental biases were correctly taken into account. The presented results could serve as a baseline for further improvements to GPS single and dual-frequency precise point positioning with WADGPS corrections. Furthermore, the developed processing software can be used to monitor WADGPS performance anywhere in the service coverage area using observations from independent permanent networks. The receivers need not be equipped for WADGPS.
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:	1470 - 1482
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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