GPS Application to Time Transfer and Dissemination

The Global Positioning System (GPS), in addition to providing precise navigation and positioning information, produces precise time and frequency measurements. These measurements result from the atomic clocks in the GPS satellites, which are closely coupled to Universal Coordinated Time as maintained by the U. S. Naval Observatory UTC(USNO)]. The application of these measurements to timekeeping and other systems requiring precise time and frequency is distinct from the navigation/positioning mission. This article will describe the differences in application of GPS to time and frequency uses. These uses will be described in the major areas of timekeeping; stationary uses, such as communications networking; and mobile use for aircraft and shipboard applications. The major considerations in application and operation with precise and less-capable oscilators will be described. Examples and data will be presented to illustrate the applications. ? 1999 John Wiley & Sons, Inc.