Spatial and Temporal Characteristics of DGPS Carrier Phase Errors Over a Regional Network

G. Fotopoulos and M.E. Cannon

Abstract:	As the distance between a GPS mobile user and a reference receiver increases, differential GPS (DGPS) positioning errors become more decorrelated. These distance dependent errors include ionospheric, tropospheric, and satellite orbit errors that do not cancel or reduce as they do for short baseline cases. This limits the ability for carrier phase ambiguities to be resolved and results in a poorer positioning accuracy. Using multiple reference receivers, the overall performance has improved in terms of time to fix integer ambiguities as well as accuracy. Recently a novel method, developed at the University of Calgary, which uses multiple reference receivers to reduce code and carrier phase differential measurement errors was introduced. This method involves the generation of corrections based on the reference network and transmits them to a mobile user, which can be located anywhere within the coverage area. In order to assess the performance, it is important to know how the corrections change over the network area. This involves examining issues such as the parameterization of these corrections and the correction transmission rate. This paper investigates two methods for parameterizing corrections, namely generating a correction grid for the desired coverage area on an epoch-by-epoch basis as well as approximating the correction behavior by a low-order surface. Advantages and disadvantages associated with each method are also discussed. From a real-time implementation perspective, the correction update rate is evaluated as a function of position accuracy. Results on the spatial and temporal behavior of the errors over a network in Sweden are presented with an emphasis on the overall effect in the position domain.
Published in:	Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000) June 26 - 28, 2000 The Catamaran Resort Hotel San Diego, CA
Pages:	54 - 64
Cite this article:	Fotopoulos, G., Cannon, M.E., "Spatial and Temporal Characteristics of DGPS Carrier Phase Errors Over a Regional Network," Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000), San Diego, CA, June 2000, pp. 54-64.
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