As convenient as GPS (Global Positioning Satellite) Navigation devices are, we may not stop to think about the amazing technology that makes them possible. It all begins in space, thousands of miles above the earth’s atmosphere.

There are more than 24 GPS satellites in what is known as medium earth orbit, at a typical distance of about 12,600 miles above the earth. When powered up, your GPS Navigator or GPS Navigation system is in constant communication with at least one of these satellites, using the data it receives to calculate your vehicle’s location, speed and direction of travel (in technical jargon, the satellites are said to provide “autonomous geo-spatial positioning” data.) As GPS technology becomes more widespread, it is being used not only for vehicle navigation, but in the land surveying and map making industries, as well in the study of earthquakes.

According to NASA: "Southern California have installed in an array to monitor the strain accumulation in Southern California's crust. This is done with the help of the highly accurate measurements made by the GPS system which allow scientists to record millimeter-scale slip on faults that cannot ordinarily be measured.”

The official name of this satellite constellation is the NAVSTAR GPS (Navigation Satellite Timing and Ranging Global Positioning System.) To provide the most accurate signal and data, your GPS receiver will rely on as many satellite signals as possible, in a process called “tracking.” When at least three satellites are above the horizon, a process called “trilateration” occurs, with your GPS device and the satellites doing some high level computations for you while you drive your vehicle.