Day-boundary discontinuity elimination method of PPP time transfer with “0 to 0” orbit and clock products

Day-boundary discontinuities at 00:00 in daily GNSS orbit and clock products can introduce nanosecond-level jumps into precise point positioning (PPP) clock estimates and degrade the continuity of station-to-station time transfer. Leveraging recently released “0 to 0” products, this study proposes a new processing strategy that explicitly uses the precisely determined day-boundary jumps. The method first computes the satellite-wise orbit and clock discontinuities at 00:00 from two consecutive “0 to 0” files, then distributes these jumps over a short correction interval on the second day and applies a small process noise to the ionosphere-free ambiguities so that they gradually absorb the residual boundary-induced errors. The approach is implemented within a PPP time-transfer framework and evaluated using 31 days of COD final and GBM rapid products, together with GPS and Galileo observations from four IGS stations forming three time-transfer links. Conventional PPP processing produces clock jumps ranging from less than 1 ns to approximately 6 ns. The proposed method effectively removes these discontinuities while preserving subsequent clock variations. For the three links, the mean absolute difference between the results at 00:00:00 and 00:00:30 decreases from 0.056-0.225 ns to 0.012-0.027 ns, corresponding to reductions of approximately 79-93%. The corrected results are also consistent with COD precise receiver-clock products within 1 ns. These findings demonstrate that the proposed strategy provides a practical way to achieve nanosecond-level continuity across day boundaries in GNSS-based time transfer.