• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.4
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• pp.383-390
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• 2004

IGS provides so accute a final precise ephmerides which is offered in the 13rd, and it also offers a rapid precise ephmerides for more prompt application and an ultra-rapid precise ephmerides for real-time application. The purpose of this study is to analyze the accuracy of a rapid precise ephemerides and an ultra-rapid precise ephemerides based on a final precise ephmerides and determine the degree of the Lagrange Interpolation which needs to decide the location of a satellite. As the result of this study, the root mean square error of x,y,z coordinates of a rapid precise ephemerides was $\pm$0.0l6m or so, and the root mean square error of an observed ultra-rapid precise ephemerides was approximately $\pm$0.024m. The root mean square error of an ultra-rapid precise ephemerides predicted for 24 hours was $\pm$0.07m or so and the one of an ultra-rapid precise ephemerides predicted for 6 hours was $\pm$0.04m or so. Therefore, I could figure out that it had higher accuracy than a broadcast ephemerides. Also, in case that the location of a satellite was calculated with the method of the Lagrange Interpolation, it was confirmed that using the 9th order polynomial was efficient.

• Journal of Advanced Navigation Technology
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• v.15 no.6
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• pp.953-961
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• 2011

IGS (International GNSS Service) predicted orbits contained in IGS ultra-rapid orbits is suitable for real-time or near-real-time precise positioning. In this paper, we analyzed orbit anomalies of the IGS predicted orbits and detected the anomalies NANU (Current Notice Advisories to NAVSTAR Users) messages and IGS BRDC (Broadcast Ephemerides). As a results, the orbit anomalies of the predicted orbits were observed 93 times in 2010. In case of using the NANUs, we could get detection performance of 88% about the IGS predicted orbits's anomalies. And we could achieve 95% detection performance when the NANUs and BRDCs were used together.