Use of a Covariance Analysis Technique for Predicting Performance of Regional Area Differential Code and Carrier-Phase

J. Raquet, G. Lachapelle, L. P. S. Fortes

Abstract:	There is currently great interest in using regional area ref-erence receiver networks (on the order of hundreds of km) to perform precise (10 cm or better) kinematic position-ing using GPS carrier-phase measurements. This has been brought about by the proliferation of existing reference re-ceivers, and an ever increasing desire for improved accu-racy. The performance of a regional area reference receiver net-work is a function of many different considerations includ-ing a) the number/geometry of the reference rece, . S, b) the number/geometry of the visible satellites, c) the posi-tion of the mobile user relative to the reference receivers, d) the magnitude/correlations of the ionospheric, tropo-spheric, and satellite position errors, and e) the characteris-tics of the multipath and receiver noise. When designing or using a regional area reference receiver network, it is important to be able to make design trade-offs of all these factors, which involves predicting what the errors will be under various network configurations. In this paper, a method for predicting the level of differ-ential (double-difference) code and carrier-phase errors is presented, which is able to take all of these considerations into account. This method uses a covariance analysis tech-nique which is based upon a network differential algorithm that minimizes the differential error variances (The “Net-Adjust” method). The covariance analysis method is first validated by com-paring its predicted results with actual results obtained from a real-world network of 11 GPS receivers spread over a 400 km x 600 km area. Then, the covariance analysis is applied to a number of “what if” scenarios (e.g. What if there was an additional reference receiver here’? What if chokering antennas were used’? What if the mobile user is located here’?). This demonstrates the usefulness of this ap-proach when designing or using a regional area differential GPS network for precise positioning.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	1345 - 1354
Cite this article:	Raquet, J., Lachapelle, G., Fortes, L. P. S., "Use of a Covariance Analysis Technique for Predicting Performance of Regional Area Differential Code and Carrier-Phase," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1345-1354.
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