Precise time scales and navigation systems: mutual benefits of timekeeping and positioning

Abstract

The relationship and the mutual benefits of timekeeping and Global Navigation Satellite Systems (GNSS) are reviewed, showing how each field has been enriched and will continue to progress, based on the progress of the other field. The role of GNSSs in the calculation of Coordinated Universal Time (UTC), as well as the capacity of GNSSs to provide UTC time dissemination services are described, leading now to a time transfer accuracy of the order of 1–2 ns. In addition, the fundamental role of atomic clocks in the GNSS positioning is illustrated. The paper presents a review of the current use of GNSS in the international timekeeping system, as well as illustrating the role of GNSS in disseminating time, and use the time and frequency metrology as fundamentals in the navigation service.