Determination of Un-Differenced Atmospheric Delays for Network-Based RTK

B. Zhang

Abstract:	Network-Based RTK technique can deliver centimeter level’s positioning accuracy almost instantaneously. However, in order to fulfill such target, determination of atmospheric delays (mainly ionospheric and tropospheric delays) between the reference stations is one of the most important prerequisites: Such estimated atmospheric delays will be interpolated at the rover stations for fast ambiguity resolution and further, precise positioning purpose. If more precise atmospheric delays’ determination technique can be realized, the distance from the reference stations that the Network-Based RTK can be performed would be greater, which will make the Network-Based RTK technique much more economic and effective. In this contribution, a new approach is proposed for precisely determining Un-Differenced (UD) atmospheric delays between the reference station networks in real-time. For this purpose, the kalman filter model is adopted; the estimable state vector includes the single-channel Ionospheric Slant Delay and the Zenith tropospheric Wet Delay (ZWD) at every reference station. The dynamic variation characteristics of the state vector are taken into consideration in the dynamic model of the kalman filter, of which the constant velocity model and random walk process are adopted respectively to depict such characteristics of these two kind parameters; Re-parameterized UD GPS observation equations are adopted as the observation model of the kalman filter, which facilitate estimating the atmospheric delays in UD mode and utilizing the constraints of fixed Double-Differenced (DD) ambiguities and a-priori known coordinates of the reference stations. Several different schemes are designed to verify the proposed approach through the experimental reference station network data; Compared to traditional approach of Network RTK, in which the DD atmospheric delays were estimated, the UD counterparts derived from our method could be much more precise and suitable for senior physical modeling, this is very beneficial for the interpolation process at the rover end.
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:	2727 - 2738
Cite this article:	Zhang, B., "Determination of Un-Differenced Atmospheric Delays for Network-Based RTK," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 2727-2738.
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