Algorithm for Carrier Adjusted DGPS Positioning

Xin-Xiang Jin

Abstract:	This paper derives a DGPS positioning algorithm, referred to as algorithm for carrier adjusted DGPS positioning. This algorithm can be applied by a DGPS user when code andcarrier observations are available and when dynamic behaviours of mobile positions and receiver clock biases can or cannot be modelled. Since the algorithm directly uses code and carrier observations, rather than the so-called carrier-smoothed code observations, the stochastic model of observations has a simple structure and can be easily specified. When the dynamic behaviour of mobile positions can be modelled, the algorithm can provide recursive solutions of the positions. Whereas when the behaviour cannot be modelled, it can provide their instantaneous solutions. Furthermore, the algorithm can be integrated with a real time quality control procedure so that the quality of the position estimates can be guaranteed with a certain probability. Since in the use of the algorithm there always exist redundant observations unless the position parameters are not estimable, the quality control can even be performed when only four satellites are tracked. By using the algorithm and real GPS data collected at a loo-km baseline, this contribution investigates how DGPS positioning accuracies vary with the number of observables used at reference and mobile stations and how important it is to choose an elevation-dependent standard deviation for code observations in DGPS data reduction. It is found that using carrier observations along with code observations is more important at the reference station than at the mobile station. Choosing an elevation- dependent standard deviation for code observations can result in better positioning accuracy than choosing a constant standard deviation for code observations. For the loo-km baseline, half-metre single epoch positioning accuracy was achieved, when dual-frequency data was used at both reference and mobile stations. The positioning accuracy became better than 7.5 decimeters, when the types of observables used at the mobile station were replaced by Ll code and carrier.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	405 - 414
Cite this article:	Jin, Xin-Xiang, "Algorithm for Carrier Adjusted DGPS Positioning," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 405-414.
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