Comparisons Via Global Positioning System Satellites in Common-View

Abstruct-Frequency differences between major national timing cen-ters are being resolved with uncertainty of less than 1 part in 1014;using satellites of the Global Positioning System (GPS) in common-view. Por-table clock and GPS time differences are in excellent agreement. Around the world GPS measurement between three laboratories had a time resid-ual of 5.1 ns. MONG the units of the International System (SI) the A second, or its inverse the hertz, is unique in that local time is the integral of the frequency generated by an SI stan-dard for the second. Because of this integral relationship, and taking advantage of the heterodyne principle wherein signifi