The Analysis of Character of User Range Accuracy
The new generation of Global Positioning System (GPS) plans to use user range accuracy (URA) as the integrity monitoring parameter of the signal in space. In the future, the system can forecast and monitor user range error (URE), which results from the si
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The Analysis of Character of User Range Accuracy Yuechen Wang and Rui Li
Abstract The new generation of Global Positioning System (GPS) plans to use user range accuracy (URA) as the integrity monitoring parameter of the signal in space. In the future, the system can forecast and monitor user range error (URE), which results from the signal-in-space error (SISE), including ephemeris error and clock error. By this way, system can reduce the space segment incidents’ impact for navigation users effectively. URA is an original parameter of GPS’s message, but its definition and application are changing all the time. In this paper, we firstly summary various changes of the URA, include not only the definition and the application, but also the refining of the index. Then, for the sake of finding the reasons of these changes, we make statistics on the IGS’s broadcast and precise ephemeris from 2002 to 2012. By analyzing the character of SISE and URE, we get conclusions below: because of the accuracy’s improvement of ephemeris and clock, the accuracy of URA must be improved. What’s more, the URE’s mean is non-zero, by the using of the concept of ‘‘bound’’, the using of original URA will lead to an exaggerated bound so that it can’t reflect the integrity of the system. We can use the concept of error ellipsoid to explain this phenomenon effectively. Keywords GPS
User range accuracy Integrity monitoring Error ellipsoid
24.1 Introduction GPS is a satellite navigation system of USA. So far, it is widely used in the field of measurement, navigation, meteorology and so on. Besides the improvement of the system’s accuracy, the real-time, continuity and integrity abilities have attracted Y. Wang (&) R. Li School of Electronic and Information Engineering of Beihang University, Beijing 100191, China e-mail: [email protected]
J. Sun et al. (eds.), China Satellite Navigation Conference (CSNC) 2013 Proceedings, Lecture Notes in Electrical Engineering 244, DOI: 10.1007/978-3-642-37404-3_24, Springer-Verlag Berlin Heidelberg 2013
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more and more attentions. Especially, in the context of the civil aviation applications, the system’s integrity performance is particularly important. The integrity means, when the navigation system can’t be used, it must have the ability of alarming users in time [1, 2]. The integrity monitoring includes three important parameters: integrity risk, alarm time and alarm threshold [2]. The new generation of GPS system plans to use user range accuracy (URA) as the integrity monitoring parameter of the signal in space. In order to achieve this goal, GPS has carried out a series of changes on URA. In this paper, we firstly search the literature and list the changes of the definition and applications of URA. Then, according to the statistics of data, we analyze the reasons of all changes by using the error ellipsoid, which can show the significance of the changes for integrity monitoring. All of the studies will contribute to a better understanding of the application o
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