An empirical approach to study the effects of a priori observations sigma ratio in single frequency precise point positioning

Choy, S, Zhang, K, Silcock, D and Holden, L 2008, 'An empirical approach to study the effects of a priori observations sigma ratio in single frequency precise point positioning', in Tomoyuki Miyano, Jianxin Li (ed.) Proceedings of the International Symposium of GPS/ GNSS 2008, Odaiba, Japan, 11-14 November 2008.


Document type: Conference Paper
Collection: Conference Papers

Title An empirical approach to study the effects of a priori observations sigma ratio in single frequency precise point positioning
Author(s) Choy, S
Zhang, K
Silcock, D
Holden, L
Year 2008
Conference name International Symposium on GPS/ GNSS 2008
Conference location Odaiba, Japan
Conference dates 11-14 November 2008
Proceedings title Proceedings of the International Symposium of GPS/ GNSS 2008
Editor(s) Tomoyuki Miyano, Jianxin Li
Publisher International Symposium on GPS/ GNSS
Place of publication Japan
Abstract Single frequency Precise Point Positioning (PPP) is a high accuracy absolute point positioning technique, which aims to provide positioning solutions comparable to the code-based relative positioning technique. Like all Global Positioning System (GPS) processing, single frequency PPP data are processed based on (weighted) least squares principle, whereby users need to specify the observations equations and observations weight matrix. Numerous research in observation equations have been undertaken and documented over recent years. However, research in observations weight matrix has received considerably less attention (Teunissen, 1998; Tiberius, 1999). In this research, the implemented observation equations for single frequency PPP are, in addition to the L1 code observations, the combination of L1 code and carrierphase observations, known as the quasi-phase observable (Simsky, 2006). The quasi-phase observable is based on the average of the code and carrier phase observations, which forms the single frequency ionosphere-free code and phase delay. Due to the nature of the quasi-phase observables, the sigma (standard deviation) ratio between the code observations and the quasi-phase observations is far from trivial. This paper aims to study the contributions of a priori observations sigma ratio on single frequency PPP solutions, typically in Australia. The effects of different sigma ratios will be evaluated based on the estimated point positioning accuracy and precision, as well as the overall convergence behaviour. At present, research into the stochastic behaviour of single frequency PPP code and quasi-phase observables is still in its early stage. To assess the impact of different sigma ratios on the estimated solutions, three case scenarios with different ratio values were formulated and tested. The sigma ratios selected were 1:100, 1:50, and 1:10 (i.e. code:quasiphase). GPS data used in this experiment were collected at three Australian IGS stations. For each station, data from a total of 18 randomly selected days within the years from 2001 to 2006 were used. The results showed that the a priori code and carrier phase sigma ratio values affect the accuracy, precision, as well as the convergence behaviour of the estimated solutions. Therefore, it is important to assign an a priori code and quasi-phase ratio that adequately reflects the “relative” relationship between the observations in order to enhance and improve the point positioning solutions.
Subjects Navigation and Position Fixing
Geodesy
Surveying (incl. Hydrographic Surveying)
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