Analyzing the Impacts of Galileo and Modernized GPS on Precise Point Positioning

X. Shen and Y. Gao

Abstract:	GPS has found a wide range of applications in our daily life. But it has limitations: easily blocked signals; insufficient accuracy for some applications; insufficient reliability for 'safety of life' applications, and the concern that GPS could one day be denied to civilians or non-US users. The launch of Galileo could overcome all these limitations. Interoperability and Compatibility is an important issue for GPS-Galileo integration. Galileo/GPS interoperability is partly realized by a partial frequency overlap with different signal structures and/or different code sequences, as well as considerations on geodetic and time references between the two systems. Several advantages with the future combined GNSSs are: more observations, new signal structures and greater power level. These will bring significant improvements on the performance of Precise Point Positioning (PPP) processing. The much lower code noise level and higher redundancy could reduce not only the ambiguity convergence time but also the positioning errors. This paper will analyze the impacts of Galileo and Modernized GPS on PPP via simulation method. PPP processing is evaluated under three scenarios: GPS only, Modernized GPS, and GPS+Galileo integration. The GPS and Galileo measurements are generated using a Matlab toolbox developed by GPSoft. The simulated errors in the measurements include troposphere, ionosphere, clock error, receiver noise and system-time offset. The obtained results indicate that the combined system has a significant improvement in positioning accuracy, 75% improvement in both horizontal and vertical components over the GPS alone system. The combined system can also improve the position convergence performance in PPP, reducing more than half of the convergence time compared to the GPS alone system. As whether to estimate GPS-Galileo system time difference, it causes only limited impact on the PPP performance.
Published in:	Proceedings of the 2006 National Technical Meeting of The Institute of Navigation January 18 - 20, 2006 Hyatt Regency Hotel Monterey, CA
Pages:	837 - 846
Cite this article:	Shen, X., Gao, Y., "Analyzing the Impacts of Galileo and Modernized GPS on Precise Point Positioning," Proceedings of the 2006 National Technical Meeting of The Institute of Navigation, Monterey, CA, January 2006, pp. 837-846.
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