GPS is short for Global Positioning System. Basically, a GPS is a device that receives signals from three or more orbiting satellites to tell the user exactly where he is and guide him to another specific location. As many as 24 satellites circle our earth in very precise orbits, making the information they transmit extremely accurate.
When the receiver is locked onto 3 satellites, it can give longitude and latitude direction position that is accurate to within 15 metres. If four or more satellites are used the GPS can also give an altitude position. Once position is determined, other information such as speed, trip distance sunrise and sunset can be calculated. Newer types that use the Wide Area Augmentation System (WAAS) are accurate to 3 metres. The Differential GPS (DGPS) used by US coastguards are also accurate up to three metres.
The GPS was first developed by the US Department of Defence for military purposes, but the government decided to release it to the civilian population. It has certainly taken the worry out of negotiating traffic and driving to a strange destination. Instead of listening to endless human instructions that may or may not be clear and right, we can now depend on those satellites zooming invisibly overhead to get us to our destinations.
