A simple method for calibrating GPS-disciplined clocks via direct comparison to a UTC(k) time scale

Abstract

Global-Positioning-System-(GPS) disciplined clocks are referenced to the Coordinated Universal Time (UTC) scale at the United States Naval Observatory (USNO), known as UTC(USNO). The UTC(USNO) time scale is a very close approximation of UTC, the official world time scale. GPS-disciplined clocks therefore provide a very close approximation of UTC when they are properly calibrated to compensate for equipment and cable delays. This paper provides a simple method for calibrating GPS-disciplined clocks with respect to UTC so they can replicate UTC with uncertainties of < 10 ns. The method involves directly comparing the device under test to any UTC(k) time scale listed on the weekly Rapid UTC (UTCr) reports published by the Bureau International des Poids et Mesures (BIPM).