A Sat Nav, which means Satellite Navigation, is a small portable radio receiver. The first Sat Nav devices looked like mobile phones. You held them in your or put them in your pocket Nov we find Sat Nav devices in cars, aeroplanes, and boats, and most mobile phones have Sat Nav built into them. Modern Sat Nat devices, for example the popular Garmin Sat Nav systems. have accurate electronic maps, so you know exactly where you are. For example. they can even tell you the names of the streets in a city. We switch on. And their electronic voice voice guides us to our destination