Zero-difference Integer Ambiguity Fixing on Single Frequency Receivers

D. Laurichesse, F. Mercier, J-P. Berthias

Abstract:	In the integer phase ambiguity fixing method introduced by Laurichesse and Mercier [1,2] the addition of pseudorange information to the usual GPS phase data makes it possible to directly fix integer ambiguities on zero-difference dualfrequency phase measurements. Once integer ambiguities are resolved, all phase measurements become unambiguous pseudorange-like measurements with millimeter noise level. These unambiguous phase measurements combined with precise GPS satellites ephemeris such as those produced by the IGS then allow the computation of global clock solutions over regional or even world-wide networks. The GPS satellite clocks obtained in this fashion have an interesting property: they allow the positioning of any receiver using a Precise Point Positioning (PPP) like method, with ambiguities estimated as integers. In the paper we extend the previous studies to the single frequency case. New specific combinations of observable quantities are introduced on each frequency. With the aid of the accurate dual-frequency integer phase clocks, new slowly varying satellites biases are identified. These biases exhibit strong signatures at the GPS orbital period. The ‘integer’ property of these biases is then demonstrated, that is their capability to help fix integer ambiguities using zero-difference single frequency phase data. This property is true for receivers which are part of the network used to produce the integer clocks, as well as for receivers outside of this network. This property is very important since it allows the use of the ‘integer PPP’ method, even for single frequency receivers. The precision of the corresponding positioning solution is only at the decimeter level, but it shows improved stability with respect to the standard solution. A difference in C1 satellite biases is also shown to exist between the Ashtech- and Trimble-like families of receivers. This is likely due to differences in the way these receivers perform their measurements.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	2460 - 2469
Cite this article:	Laurichesse, D., Mercier, F., Berthias, J-P., "Zero-difference Integer Ambiguity Fixing on Single Frequency Receivers," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 2460-2469.
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