A Sat Nav, or satellite navigation device, such as the Mio Moov uses the global positioning system (GPS) to pinpoint exactly where you are on the planet. It detects signals from at least three satellites in a constellation of around 30 constantly orbiting the earth.
Using the data transmitted at the speed of light by these satellites the Navman internal electronics convert the signals into distances between the device and each of these satellites. It can then lock down its precise position using trilateration, which is essentially a mathematical formula programmed into the Sat Nav.
The same calculations give not only position, but can lock that on to a position on the device's built-in maps, it also calculates the speed and direction you are travelling, and if you happen to be in an aircraft tells you your altitude too.
The Sat Nav uses the information obtained from the GPS to overlay your exact position on to the map for the area in which you are travelling. The maps used in the Navman are regularly updated and can be downloaded to the Sat Nav device from the website.
Software built into the Sat Nav device allows you to set a destination and will guide you along the best route. The device can also read data from TMC (Traffic Message Channel) and so alert you to traffic problems on major roads and optionally give you a revised route.