scope:

TWSTFT has been recognized as the most precise and accurate means for remote clock comparisons and is thus widely used in the time and frequency community, including institutions and organizations affiliated with telecommunication administrations. In view of the progress in performance of the atomic clocks compared via TWSTFT it was found necessary to calculate corrections applied to the measurement results with a higher accuracy than considered necessary in previous editions. As the Earth is not perfectly spherical, it is considered as an ellipsoid at first approximation. For a given location, there are a single longitude and two latitudes: the geocentric latitude and the geodetic latitude. The current version takes proper care of this in the calculation of the Sagnac correction.