We use GPS every day for an ever growing list of applications ranging from trailer tracking to personal navigation. The Global Positioning System has become so integrated into modern life and business that we seldom stop to think about the incredible interplay of sophisticated technology that allows us to pinpoint the location of any given GPS receiver, anywhere in the world. Considering the level of complexity involved, GPS is an extremely reliable system. It is able to operate accurately regardless of weather conditions, in any location on earth, 24 hours a day. So how exactly does this seemingly magical system actually work?
Orbiting approximately 12 000 miles above the surface of the earth, 24 satellites, travelling at roughly 7000 miles an hour, each make two full rotations around the earth every day. They are locked into extremely precise orbits and are fully powered by solar energy. Backup batteries provide power during a solar eclipse and three additional satellites are on standby in the event that one of the others should malfunction or break down. Small rocket boosters constantly adjust the satellites’ orbit, keeping them in perfect position.
GPS receivers triangulate a position by comparing the time a signal was transmitted by a satellite, to the time it is received. This allows the receiver to calculate how far away the satellite is. By comparing the location of several satellites in space, the system is able to pinpoint the location of the receiver on earth. In order to calculate a two dimensional location – latitude and longitude – a GPS receiver needs to be locked on to at least three satellites. If it is able to connect with four or more, the receiver will then be able to determine a 3D position, constituting latitude, longitude and altitude. The system can then monitor movement over time to calculate speed and compare position with geographical information to output more information like distance to destination, or bearing. Increasingly sophisticated and compact GPS receivers have been incorporated into cellphones, laptops, tracking systems and luxury vehicles.
So the next time you check up on your fleet using a vehicle or trailer tracking system, spare a thought for the amazingly complex system at work behind the scenes.
