Since that time NAVSTAR, now commonly referred to as GPS (Global Positioning System), has revolutionised transportation around the world for mariners, pilots and car drivers alike.

The functioning of the GPS system is very simple. There are currently a constellation of 24 satellites, arranged in orbit so that four are always in line-of-sight to any spot on the Earth.

These satellites contain atomic clocks, the most accurate chronometers so far developed by mankind. These keep and broadcast a time code that is accurate to a few nanoseconds (nano = 1 billionth of a second). This time code is then received by a GPS receiver that uses the information from four satellites to triangulate its exact position. This can only be done because the atomic clocks provide such accurate time. If a clock on a GPS satellite was even just one second too slow or fast, the positioning information could be as much as 200,000 miles out (because of the distance light and therefore radio waves travels in that time).

As the timing source from GPS systems are so accurate they are ideal to be used as a reference for a NTP server. NTP (network time protocol) servers use a timing source to synchronise all machines on a network to that time. A dedicated GPS NTP server can receive the time signal from the NAVSTAR system and synchronise an entire network to within a few milliseconds.

As a consequence the GPS network was opened up freely for civilian use and is currently the world’s only fully functioning global navigation satellite system (GNSS), although Europe and Russia are to have their own systems within the next decade.

Although the GPS system is primarily used for location finding the only information it relays is the time, which has proved beneficial in keeping computer networks synchronised using a GPS NTP server.

Each GPS satellite contains an atomic clock, these clocks beam to Earth an exact timing signal, precise to a second in several millions of years. The GPS receiver then works out the time each signal took to get to it (a minimum of three is therefore needed) and can work out its exact location by this triangulation.

GPS satellites have to provide exact timing information as light and radio waves can travel 300,000 km each second, a difference which would make navigation hopeless. However, this information can be used by a GPS NTP Server which converts the time signal from the satellites into UTC (Coordinated Universal Time) and then synchronises every clock on a network to that time.

Using the GPS network means a GPS NTP server can provide accuracy to a computer network to within a few milliseconds. GPS has therefore not only transformed the way in which the world navigates but also has also revolutionised computer networks with precise timing information making possible many of the Internet  processes such as online purchasing and email that we all take for granted.

Most commonly, the GPS system is thought to provide navigational information allowing drivers, sailors and pilots to pinpoint their position anywhere in the world.

In fact, the only information beamed from a GPS satellite is the time which is generated by the satellites internal atomic clock. This timing signal is so accurate that a GPS receiver can use the signal from three satellites and pinpoint the location to within a few metres by working out how long each precise signal took to arrive.

Currently a GPS NTP server can use this timing information to synchronise entire computer networks to providing accuracy to within a few milliseconds.

However, the European Union is currently working on Europe’s own Global Navigation Satellite System called Galileo, which will rival the GPS network by providing its own timing and positioning information.

However, Galileo is designed to be interoperable with GPS meaning that a current GPS NTP server will be able to receive both signals, although some software adjustments may have to be made.

This interoperability will provide increased accuracy and may make national time and frequency radio broadcasts obsolete as they will not be able to produce a comparable accuracy.

Furthermore, Russia, China and India are currently planning their own GNSS systems which may provide even more accuracy. GPS has already revolutionised the way the world works not only by allowing precise positioning but also enabling entire globe to synchronise to the same timescale using a GPS NTP server. It is expected that even more advances in technology will emerge once the next generation of GNSS begin their transmissions.