Time Synchronisation

GPS time servers are often called many things: NTP time servers, GPS network time servers, GPS NTP servers etc. A time server is merely a device to that computer’s can contact to receive timing information from for purposes of time synchronisation.

The way a time server receives the time is what defines it. A radio referenced time server will receive a time signal from a national physics laboratory via a long wave radio signal. A GPS time server receives a time signal from the Global Positioning System a constellation of satellites designed to provide navigation information.

What makes GPS possible is that onboard each global positioning satellite there is an atomic clock. The time from this clock is broadcast along with the position and velocity of the satellite. It is this information that a satellite navigation receiver uses to work out position by triangulation. It receives the same data from three or more satellites and works out by the time it takes for the transmission from each satellite to reach the receiver.

While the atomic clocks onboard the GPS satellites do not broadcast UTC (Coordinated Universal Time - the civil global timescale) because it is an atomic clock signal and therefore extremely reliable, a GPS time server can easily translate the GPS time into UTC.

Richard Hawkesford © 2009