Parameterization of Carrier Phase Corrections Based on a Regional Network of Reference Stations

Georgia Fotopoulos

Abstract:	The purpose of this paper is to investigate various methods for parameterizing carrier phase corrections over a network of reference stations. Over the past few years, a significant amount of research has been conducted on the formulation of carrier phase corrections in order to enhance ambiguity resolution and to increase the distances over which precise positioning can be achieved. Recently the use of a network of multiple GPS reference stations for generating carrier phase based corrections has emerged with great promise for use in real-time environments. However, little research has been conducted on the distribution of these corrections to potential GPS users located within, and surrounding, the network coverage area. This is an integral part of real- time kinematic DGPS and it must be adequately addressed before a practical realization of the multi- reference station concept is implemented. Specifically, numerous options for communicating these corrections to a user(s) in an efficient and accurate way are presented. Combined corrections containing effects of correlated differential GPS errors (ionospheric, tropospheric and satellite orbit) are computed using the NetAdjust method, developed at the University of Calgary. Two main parameterization techniques are discussed, namely (1) grid-based interpolation and (2) low-order surface modelling. A permanent operational array of GPS reference stations located in southern Sweden is used for the analysis, which is performed in both the correction and position domains. The analysis concentrates on forming a solid understanding of the behaviour of the carrier phase corrections over the coverage area, with a focus on the spatial characteristics of the corrections. Results show that by using a 0.5° × 0.5° grid spacing, the corresponding position accuracies for a user receiver(s) located within the coverage area shows an improvement with respect to the single baseline approach of 20%, 54%, and 27%, in latitude, longitude and height, respectively. An alternative method of generating a best-fit low order surface to model the corrections can also lead to an improvement in position accuracies compared to some of the sparse grid-based approaches. Finally, conclusions on the spatial correlation of carrier phase corrections, based on the results presented as well as real-time data transmission bandwidth concerns are discussed.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	1093 - 1102
Cite this article:	Fotopoulos, Georgia, "Parameterization of Carrier Phase Corrections Based on a Regional Network of Reference Stations," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 1093-1102.
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