Precise Ephemerides for Gps Time Transfer
نویسنده
چکیده
The present technology of atomic clocks rnotivatcs time transfer tcclrniques with nanosecond accuracy. Global Positioning System (GPS), the most colllnlon means for international time comparisons could achieve such acciiracy ovthr short, rlista~lccs (up to 1000 km). Over intercontinental distances the accuracy of the GPS tirrlc: transfer ranges between 20 and 30 ns. Some of the principal error sources are the 1)rnadcast ephemerides, the broadcast ionospheric model, and the local a~ltenna coordinates. This study investigates the quality of broadcast ephemerides hy cornparir~g the111 with precise ephemerides and by using precise ephcrncridcs for time transfer. Another aspect of this work is to suggcst a strategy to overcome the plarlrled d~grnclat inxl of GPS satellite messages via Selective Availability (SA).
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