New devices make it easier to get around than ever before, but how do they work?
The Global Positioning System (GPS) is a satellite navigation system that was originally placed into orbit by the US Defence Force to assist soldiers, military vehicles, planes and ships in accurately determining their locations worldwide.
GPS is made up of a network of 24 satellites (with about six spares) that circle the earth twice a day from 19,308 kilometres above us. Each satellite moves at 11,000 kilometres per hour while continuously transmitting time-based signals to earth that indicate its location. A GPS device receives this information from three or more satellites and, using triangulation principles, calculates the distance between each satellite and itself to determine its exact position, orientation, and speed of travel.
GPS provides basic information of longitude, latitude and altitude, but once you marry that information up to accurate digital maps, you open up a world of navigation possibilities. Once a GPS device knows where you are, it can pinpoint that on a digital map as well as provide walking or driving directions to any other position on that map.
GPS works in most weather conditions, anywhere in the world, 24 hours a day, providing you have a direct line of sight to three or more satellites. There are no subscription fees or set-up charges to use GPS, making it accessible to anyone who has a GPS-enabled device. These can range from fully installed, in-car units, to portable systems that attach to windscreens and all the way down to handheld units embedded in many popular models of mobile phone.
The possible uses for GPS technology are as unlimited as your imagination. It is already being used in balloons to monitor the hole in the ozone layer, for tracking endangered species and, attached to buoys, keeping a trace on major oil spills during clean up operations.
How accurate is GPS?
The accuracy of GPS depends on the number of satellites in view, and signal interference caused by buildings and other geographical obstacles, such as tunnels and mountains. Most makers of GPS devices claim that, under ideal conditions, accuracy should be within 3-5 metres, provided the receiver in the GPS device has a clear shot at a minimum of four satellites.