On improved GPS-based calibration of the time links between metas and PTB

We report the results of a differential calibration of the time links between the Swiss Federal Office of Metrology (METAS) and the German Physikalisch Technische Bundesanstalt (PTB) in 2009 using a travelling state of the art GPS time and frequency transfer receiver. Neglecting possible long term variations of the GPS equipment, the estimated uncertainties of the calibration values are below 2 ns for all links. The results are verified by comparing them to the calibrated two way satellite time and frequency transfer (TWSTFT) link. Thereby it appears that, vice versa, a GPS calibration via a travelling receiver can indeed be used to calibrate a TWSTFT link with an uncertainty below 2 ns.