navigation par satellite

CONT: La navigation par satellite est une technologie clé qui permet à une personne d'indiquer précisément sa position géographique sur terre, sur mer et dans les airs. Elle offre de nombreux avantages dans une multitude de domaines comme le transport (plus grande sécurité, réduction de la congestion et des dommages à l'environnement, etc.), la médecine (traitement de patients à distance, etc.) et l'agriculture (ajustement des doses de grains selon le relief, etc.).
OBS: navigation par satellite : terme uniformisé par le Comité de normalisation de la terminologie navale (1994), et adopté par la Commission française des techniques aérospatiales (1998).

CONT: Satellite navigation. ... 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.