Time Restitution and Transfer with GPS and Galileo

Abstract

In the last decade GPS has become a widely accepted tool in both metrological and commercial timing applications. Thus, GPS-based time transfer – the so called Common View – is used to measure the offsets between time scales maintained in national metrology institutions. Another example is the utilization of GPS time receivers at GSM base stations to produce a precise time and frequency reference for their operations. Therefore, at its advent Galileo will find itself in a well established application framework oriented on and partially formed by GPS. The way to ease the Galileo introduction into the market appears to be two-fold: on one hand, Galileo should demonstrate high accuracy and reliability of its services to the timing community, and on the other hand the possibilities of Galileo combination with GPS (with the focus on benefits of this combination) require a careful investigation. In this paper, we revisit the accuracy of timing for Galileo users and discuss problems related to the combination of Galileo with GPS.