PPP and phase-only GPS time and frequency transfer

The Royal Observatory of Belgium (ROB) developed the software Atomium to perform GPS-based time and frequency transfer. Originally dedicated to perform Precise Point Positioning (PPP) based on a combined analysis of dualfrequency carrier phase and code measurements, Atomium has recently been adapted to allow a phase-only analysis, providing a continuous solution independent of the GPS codes. In this paper, the analysis strategy used in Atomium is described and the clock solutions obtained through the phase-only approach are compared to the results from the PPP mode. It is shown that the continuous solution improves the stability of the time link for averaging times smaller than 7 days, but that the phase-only solution is drifting with respect to the combined code-carrier phase solution; this drift is station-dependent. © 2007 IEEE.