GPS or Global Positioning System is the only functioning satellite-based navigation system on the planet. GPS consists of a network of two to three dozen satellites in space. GPS was first used by the United States military as a means of tracking personnel on the ground and for sending information to ground troops.
The military put several dozen satellites in orbit and these satellites are what run every GPS device on the planet today. The EU (European Union), Russia, India and China are all trying to develop a competing system, but as of now, no one has succeeded.
The workings of GPS are not that difficult to understand. A GPS receiver here on earth, whether it is a hidden GPS device in your car, or built into a hand held device, receives microwave signals from the orbiting satellites. These signals contain the position of the satellite and the time of the transmission. The receiver then triangulates itself to the signals to show its location here on earth.
The GPS signals are somewhat weak, so certain forms of electromagnetic interference can disrupt the microwave transmissions. Solar flares or other magnetic events that naturally occur in nature can also disrupt these signals, but overall, GPS is very reliable.
