A permanent reference in time and space.
More and more often, it will become necessary to ascertain one’s precise position in space and time in a reliable manner. This will be possible with the GALILEO satellite radio navigation system, an initiative launched by the European Union and the European Space Agency. This worldwide system will ensure complementarity with the current GPS system.
Satellite radio navigation is an advanced technology. It is based on the emission from satellites of signals indicating the time extremely precisely. This enables any individual to determine his or her position or the location of any moving or stationary object (e.g. a vehicle, a ship, or a herd of cattle, etc.) to within one metre thanks to a small cheap individual receiver.
GALILEO is based on a constellation of 30 satellites and ground stations providing information concerning the positioning of users in many sectors such as transport (vehicle location, route searching, speed control, guidance systems, etc.), social services (e.g. aid for the disabled or elderly), the justice system and customs services (location of suspects, border controls), public works (geographical information systems), search and rescue systems, or leisure (direction-finding at sea or in the mountains, etc.).
Satellite navigation – How does it work ?
Since time immemorial, people have looked to the heavens to find their way. Today, satellite navigation is continuing this tradition, while offering, thanks to leading-edge technology, an accuracy far beyond that possible by simply observing the sun and the stars. This technology, which has been developed over the last thirty years or so, essentially for military purposes originally, enables anyone with a receiver capable of picking up signals emitted by a constellation of satellites to instantly determine their position in time and space very accurately.
The operating principle is simple: the satellites in the constellation are fitted with an atomic clock measuring time very accurately. The satellites emit personalised signals indicating the precise time the signal leaves the satellite. The ground receiver, incorporated for example into a mobile phone, has in its memory the precise details of the orbits of all the satellites in the constellation. By reading the incoming signal, it can thus recognise the particular satellite, determine the time taken by the signal to arrive and calculate the distance from the satellite. Once the ground receiver receives the signals from at least four satellites simultaneously, it can calculate the exact position.