WorldTrack GPS, Transport Business AnyWhere, Anyplace, Anytime
The Global Positioning System (GPS) may be a network of concerning thirty satellites orbiting the planet at associate degree altitude of 20,000 km. The system was originally developed by the federal government for military navigation however currently anyone with a GPS device, be it a SatNav, mobile or hand-held GPS unit, will receive the radio signals that the satellites broadcast.
Wherever you’re on the world, a minimum of four GPS satellites square measure ‘visible’ at any time. every one transmits info concerning its position and also the current time at regular intervals. These signals, traveling at the speed of sunshine, square measure intercepted by your GPS receiver, that calculates however distant every satellite is predicated on however long it took for the messages to arrive.
Once it’s info on however distant a minimum of 3 satellites square measure, your Personal GPS Tracker receiver will pinpoint your location employing a method referred to as trilateration.
Trilateration:
Imagine you’re standing somewhere on Earth with 3 satellites within the sky on top of you. If you recognize however distant you’re from satellite A, then you recognize you need to be set somewhere on the red circle. If you are doing constant for satellites B and C, you’ll be able to total your location by seeing wherever the 3 circles meet. this is often simply what your GPS receiver will, though it uses overlapping spheres instead of circles.
The additional satellites there square measure on top of the horizon the additional accurately your GPS unit will confirm wherever you’re.
GPS and Relativity:
GPS satellites have atomic clocks on board to stay correct time. General and theory of relativity, however, predict that variations can seem between these clocks and an even clock in Earth.
General Relativity predicts that point can seem to run slower below stronger gravitative pull – the clocks aboard the satellites can, therefore, appear to run quicker than a clock in Earth.
Furthermore, theory of relativity predicts that as a result of the satellites’ clocks square measure moving relative to a clock in Earth, they’re going to seem to run slower.
The whole GPS network must create allowances for these effects – proof that Einstein’s theory of relativity includes a real impact.