Satellite Navigation   With advanced navigation systems, whether your trip takes you across town or to another country, sat nav gets you there with speed and accuracy giving you visual and verbal commands turn by turn. How does it work? Navigation systems require a GPS, (global positioning system) a speed pulse signal from your car and with a built in gyroscopic compass, along with the information stored on the CD Rom or DVD, the system registers every move you take. If you can't take a turn or miss the junction the system automatically reroutes to your destination. TMC (Traffic message channel) will even reroute you round traffic jams and congestions automatically. Inputting your address is simple, following the on screen messages you type your destination in with a predictive text system, and it eliminates unneeded letters and then completes your destination for you. Some systems have the ability to input postcodes and house numbers taking you directly to your door. Systems available from: