Are you old enough to remember life before Sat Nav? Remember when you relied on using a road map lying precariously on the passenger seat beside you. If you were like me, you got lost frequently. Now you simply type in a postcode or a road name on your phone or sat nav and you’ll be guided all the way to your destination. But do you know how GPS works? You turn it on and type in the post code. No, that is not what I mean.
The Global Positioning System(GPS) is a constellation of 30+ Earth-orbiting satellites. Weighing around 3,000 to 4,000 pound each solar-powered satellite circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day. The orbits are arranged so that at anytime, anywhere on earth, there are at least four satellites “visible” in the sky. Your GPS receiver in your sat nav locates four or more of these satellites, figure out the distance to each, and uses this information to deduce its own location. This operation is based on a simple mathematical principle called trilateration. In order to make this simple calculation, then, the Sat Nav or GPS receiver has to know two things: The location of at least three satellites above you and the distance between you and each of those satellites.Continue reading