GPS (Global Positioning System): Satellites, Monitoring Stations, and Receivers

Global Positioning System or GPS, is an extremely useful satellite radio navigation system, which is composed of satellites, Earth monitoring stations, and GPS receivers. Developed and built by the United States Department of Defense, GPS had been in the works since the 1960s, however it wasn't until the following decade in 1978, when the pioneering, first, fully operational GPS satellite was launched. With the launch and operation of the satellite marking the completion of the GPS project, the entire system came on line, and was used exclusively by the U.S. military for many years. It wasn't until the 1980s that the United States Government authorized the use of Global Positioning System by the general public, and this version GPS did not become fully operational until 1995.

At present day, there are 24 satellites in orbit around the earth, traveling in a total of six meticulously different trajectories. Every one of these satellites completes two full orbits around our planet each day, traveling at an amazingly fast speed of roughly seven thousand miles per hour. Their altitude reaches a height of over twelve thousand miles above the earth, at the highest point in their orbit. The satellites are placed at this great distance above the earth, because it is from this height that the satellite signals can span, and be received over a large percentage of the planet's surface. These signals are sent to a GPS unit, which then calculates the receiver's position, based on a simple triangulation. A minimum of four signals need to be sent to a receiver in order for accuracy to be maximized, therefore the orbits of the satellites are purposely set to allow for a fairly high probability of the receipt of this minimum amount of signals.