Time and Clock Issues in WADGPS

Sally Basker and Ian Casewell

Abstract:	Time, clocks, and time transfer or clock synchronization are of considerable importance within Wide Area Differential GPS (WADGPS). WADGPS studies undertaken to date envisage the transmission of various corrections which include ephemeris parameters, ionospheric parameters, and one set of satellite clock correction terms for each satellite viewed by multiple reference stations within the Wide Area. These satellite clock correction terms need to be related to a single clock so that they are independent of the receiver at which they were originally observed. These are then applied by multiple users in a manner analogous to the use of the pseudo-range and range-rate corrections within conventional DGPS implementations. Therefore there are two major time related activities with WADGPS: firstly, the synchronization of the multiple reference receiver clocks, thus ensuring the independence of the satellite clock corrections; and secondly, the computation and dissemination of the satellite clock corrections themselves. A large measurement campaign was carried out in May 1993 in support of a European Space Agency supported WADGPS study. This paper presents the work undertaken during the study to investigate the time and clock issues inherent in WADGPS, and will illustrate the performance of the selected processing techniques using data from the measurement campaign. It will be shown that real-time clock synchronization to an accuracy of better that 10 ns (30) may be achieved using these techniques.
Published in:	Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994) September 20 - 23, 1994 Salt Palace Convention Center Salt Lake City, UT
Pages:	1509 - 1518
Cite this article:	Basker, Sally, Casewell, Ian, "Time and Clock Issues in WADGPS," Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994), Salt Lake City, UT, September 1994, pp. 1509-1518.
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