Interpolating Residual Zenith Tropospheric Delays for Improved Wide Area Differential GPS Positioning

Yi Zheng

Abstract:	Tropospheric delay is one of the major error sources in satellite-based positioning systems. The delay of radio signals caused by the troposphere can range from 2 m at the zenith to 20 m at lower elevation angles (e.g. below 10 degrees). In current Wide Area Differential GPS systems, the tropospheric delays are corrected locally by the users with empirical tropospheric models, instead of using corrections generated from the network. This implementation results in residual tropospheric delay due to tropospheric modeling error. This paper studies the use of the Ordinary Kriging (OK) method to interpolate the residual zenith tropospheric delay (ZTD) within a wide area GPS network in an attempt to improve the positioning accuracy within the coverage. The ZTD solutions from 129 International GPS Service (IGS) sites across Europe for over 3 months were collected for this analysis. The results demonstrate that with the interpolating procedure applied to residual ZTDs, the overall standard deviations of zenith tropospheric corrections are improved from 3-4 cm, achievable with both the standard Saastamoinen and GTN model, down to 1-2 cm, while the overall bias of the Saastamoinen model is also dramatically reduced from 14 mm to nearly zero. This concludes that interpolating residual zenith tropospheric delays is an efficient way to improve Wide Area Differential GPS positioning.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	915 - 924
Cite this article:	Zheng, Yi, "Interpolating Residual Zenith Tropospheric Delays for Improved Wide Area Differential GPS Positioning," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 915-924.
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