Day-Boundary Discontinuity in GPS Carrier-Phase Time Transfer Using a Geodetic Data Solution Strategy

The global positioning system (GPS) carrier-phase (CP) technique is an accepted spatial tool for remote, precise, time transfer. However, the day-boundary discontinuity makes exploitation of the full potential of GPS CP time transfer difficult, particularly for a long time (e.g., > 1 day). For this study, we investigated the day-boundary discontinuity using geodetic data solution strategies. First, the edge effect of the satellite orbit and clock product interpolation, which caused a maximum outlier of 0.34 ns at station PTBB, was analyzed because it could eliminate outliers between successive daily clock solutions. Second, the behavior of phase ambiguity was assessed. The inconsistency in phase ambiguity between two daily receiver independent exchange format (RINEX) data points was removed by applying a phase ambiguity strategy. Finally, the day-boundary discontinuity of the receiver clock was evaluated using the GPS CP technique, both with and without inclusion of the two geodetic strategies, at 10 time links between PTBB and the other 10 stations. Compared with the classical CP solution, the outliers for two successive daily solutions could be removed using the edge effect strategy. When the receiver clocks referred to International Global Navigation Satellite System (GNSS) Service time (IGST), the day-boundary jump values without the phase ambiguity strategy were within 1.0 ns, but the jump values decreased to 0.2 ns when the strategy was applied, showing better agreement even at different time laboratories. In terms of the 10 time links, the corresponding day-boundary jump values were within 0.1 and 1.5 ns. By applying the phase ambiguity strategy, the mean jump value was decreased from −0.0999 to −0.0104 ns, and the standard deviation decreased from 0.4667 to 0.0269 ns. The day-boundary jump values at the 10 time links from MJD 57825 to MJD 57837 showed a clear Gaussian distribution.