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Impacts of Satellite Orbit and Clock on Real-Time GPS Point and Relative Positioning

School of Geodesy and Geomatics,Wuhan University, Wuhan 430079, China
Key Laboratory of Precise Engineering and Industry Surveying, National Administration of Surveying, Mapping and Geoinformation,Wuhan University, Wuhan 430079, China
State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University,Wuhan 430079, China
Engineering Safety and Disaster Prevention Department, Yangtze River Scientific Research Institute, Wuhan 430010, China
Author to whom correspondence should be addressed.
Sensors 2017, 17(6), 1363;
Received: 28 March 2017 / Revised: 7 June 2017 / Accepted: 8 June 2017 / Published: 12 June 2017
(This article belongs to the Section Remote Sensors, Control, and Telemetry)
PDF [1722 KB, uploaded 23 June 2017]


Satellite orbit and clock corrections are always treated as known quantities in GPS positioning models. Therefore, any error in the satellite orbit and clock products will probably cause significant consequences for GPS positioning, especially for real-time applications. Currently three types of satellite products have been made available for real-time positioning, including the broadcast ephemeris, the International GNSS Service (IGS) predicted ultra-rapid product, and the real-time product. In this study, these three predicted/real-time satellite orbit and clock products are first evaluated with respect to the post-mission IGS final product, which demonstrates cm to m level orbit accuracies and sub-ns to ns level clock accuracies. Impacts of real-time satellite orbit and clock products on GPS point and relative positioning are then investigated using the P3 and GAMIT software packages, respectively. Numerical results show that the real-time satellite clock corrections affect the point positioning more significantly than the orbit corrections. On the contrary, only the real-time orbit corrections impact the relative positioning. Compared with the positioning solution using the IGS final product with the nominal orbit accuracy of ~2.5 cm, the real-time broadcast ephemeris with ~2 m orbit accuracy provided <2 cm relative positioning error for baselines no longer than 216 km. As for the baselines ranging from 574 to 2982 km, the cm–dm level positioning error was identified for the relative positioning solution using the broadcast ephemeris. The real-time product could result in <5 mm relative positioning accuracy for baselines within 2982 km, slightly better than the predicted ultra-rapid product. View Full-Text
Keywords: satellite orbit impact; satellite clock impact; real-time positioning; point positioning; relative positioning satellite orbit impact; satellite clock impact; real-time positioning; point positioning; relative positioning

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Shi, J.; Wang, G.; Han, X.; Guo, J. Impacts of Satellite Orbit and Clock on Real-Time GPS Point and Relative Positioning. Sensors 2017, 17, 1363.

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