Precise GPS Shipborne Positioning Experiments with Semicodeless Receivers

Gérard Lachapelle, H. Sun, M. Elizabeth Cannon, and Chris McMillan

Abstract:	The objective of this paper is to investigate the level of performance achievable in differential and single point positioning shipbome mode with semicodeless receiver technology. The specific receiver type selected is the Ashtech Z-12 which measures pseudorange and carrier phase on both frequencies under Anti-Spoofing. The sea trials were conducted on a 70-m vessel off the coast of Vancouver Island in November 1994. The GPS measurements were made in differential mode and the distance between the shore-based reference station and the ship exceeded 100 km. The integer carrier phase ambiguities were successfully resolved and accurate reference trajectories for the ship were obtained. The DGPS measurements were also reduced using a float ambiguity and a carrier phase smoothed approach. An analysis of these solutions shows that the float ambiguity method is accurate to 10 cm (rms) in each coordinate component while the corresponding accuracy of the carrier phase smoothed solution is of the order of 1 m. The single point solutions, calculated using precise post-mission orbits and satellite clock corrections, were found to be accurate at the 1-2 m level using ionospherically corrected codeless measurements. The effect of the ionosphere on single frequency measurements is shown to bias the results in the case of the single point solution.
Published in:	Proceedings of the 51st Annual Meeting of The Institute of Navigation (1995) June 5 - 7, 1995 Antlers Doubletree Hotel Colorado Springs, CO
Pages:	613 - 620
Cite this article:	Lachapelle, Gérard, Sun, H., Cannon, M. Elizabeth, McMillan, Chris, "Precise GPS Shipborne Positioning Experiments with Semicodeless Receivers," Proceedings of the 51st Annual Meeting of The Institute of Navigation (1995), Colorado Springs, CO, June 1995, pp. 613-620.
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