Positioning Enhancement Based on a New Weighting Scheme to Solve an Ill-Conditioned Case

Y-W. Ahn

Abstract:	The unmodelled troposphere is a limiting but crucial factor in achieving high-precision positioning solutions for dual-frequency GPS observables. Typically, the effect is minimal in a relative positioning scenario when the baseline length is short enough, e.g. less than 10 km. However, when there is strong tropospheric anomaly, the effect will not be nominal and the GNSS solution will have a much reduced precision. As the troposphere and resultant height component are both zenith dependent, the problem exists of how to correctly de-correlate those two parameters in order to achieve better coordinate solutions especially in vertical component. There are many different approaches to solve the typical ill-conditioned case such as an orthogonal transformation. One of the innovative ways to de-correlate those parameters, proposed in this research, is to use different weighting parameters either on the troposphere or on the height component. This methodology can be realized as GPS signals can be separated in two different components: frequency-dependent and frequencyindependent realm. The troposphere is of the frequencyindependent domain in GPS signals, and this characteristic is to be further used as a weighting scheme through the residual analysis. The only assumption when using this method is that the both L1 and L2 observables are made available from a dual frequency receiver. To examine the feasibility of this method, anomalous data collected in Southern Texas, USA, on August 21, 2005 over a baseline length of around 7.8 km is reprocessed. Consequently, the positioning solution from the new proposed parameter is tested, evaluated, and compared with that from the conventional estimation method. In this paper, we have examined the feasibility of our proposed method whether it also is resistant to the anomalous tropospheric case or not. By using this methodology for the tropospheric delay mitigation, positioning improvement can be achieved in 20% in the vertical component. In addition, degradation of the vertical component due to the tropospheric anomaly is significantly reduced.
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:	2559 - 2567
Cite this article:	Ahn, Y-W., "Positioning Enhancement Based on a New Weighting Scheme to Solve an Ill-Conditioned Case," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 2559-2567.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In