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Since the early 1990’s the Global Positioning system (GPS) has been the worlds’ only fully functioning Global Navigational Satellite
System (GNSS). Run by the American military, GPS (sometimes referred to as NAVSTAR) has allowed accurate timing and location finding all
over the world.
GPS works by using a constellation of satellites (at least 24) which circle the Earth and relay precise timing information from onboard
atomic clocks down to Earth.
A GPS receiver will pick up this time signal from at least three satellites where it can triangulate its exact position by working out
how long each timing signal takes to reach the receiver.
GPS is owned and run by the US military and broadcasts at least two continual signals L1 for military use and L2 for civilian
(although an upgrade programme is currently underway which will expand the number of frequencies GPS will relay).
GPS is not only used for location and direction information the time signals are now used by millions of computer servers using Network
Time Protocol (NTP) to synchronise their devices to absolute time UTC (the international standardised time scale – Universal Coordinated Time)
Satellite navigation has become such a popular and essential tool in aviation, sea-faring and now even motoring; that many nations have felt that
it is too important a technology to rely on a foreign nation to provide (the US).
In 2002, the European Space Agency and European Union agreed to build Europe’s own GNSS called Galileo. Despite many political wrangling about
costs and who will pay for what the programme is now well underway with positioning and timing information expected to begin broadcasting in 2012
to 2013.
A Russian based system known as GLONASS, which was fully operational during the cold war but has since fallen into disrepair after the collapse
of the Soviet union, is also being revived while the Chinese have started their own GNSS system called COMPASS which would mean within a decade up
to four GNSS systems could be globally active.
To compete with the new and more advanced GNSS technologies the GPS programme is currently being upgraded and it is expected that when Galileo
begins relaying signals both systems will become interoperable allowing even more accuracy in timing and positioning.
GPS has already revolutionised the way the world works not only allowing precise global positioning but also allowing the entire globe to synchronise
to the same timescale using NTP servers. It is expected that even more advances in technology will emerge once the next generation of GNSS begin their
transmissions.
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