GPS receiver receives the signals from a a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails). Initially the system was devised for military purpose but later it was opened for commercial use.
These satellites circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites "visible" in the sky.
A GPS receiver locate four or more of these satellites, figure out the distance to each, and use this information to deduce its own location. Whole operation works on a mathematical principle called trilateration. Trilateration in three-dimensional space can be a little tricky, so we'll start with an explanation of simple two-dimensional trilateration.
When GPS receiver is used in Smartphone or PDA or Laptop it transforms them into a satellite navigation tool. Using appropriate software you can navigate freely anywhere. You can locate your exact location using GPS receiver in your PDA, Laptop or smart phones. There are many software available that helps you in loading maps of various cities and points of interests in your GPS device.
On the basis of functioning GPS receiver can be categorized as:
- Bluetooth GPS receiver
- USB GPS receiver'
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