sat nav???

[ianthe plumb]

how does sat nav work in your car does it come through your car ariel??

[re1314]

No - it's usually done using GPS and/or TrafficMaster.
The SatNav unit has a GPS unit inside it (or plugged into it) which it uses to locate your car on the map, which is stored in the SatNav unit (I think).
The TrafficMaster system monitors UK traffic and sends that information to another reciever in your car (I think).

Have you ever seen those blue cameras by the side of the road? They sometimes have aerials on top. Or the blue camera-like things hanging off the back of motorway bridges? Those are all TrafficMaster units, keeping an eye on the road/congestion conditions.

[wacky racer]

the GPS receiver is either attached to (by cable) or built in to the SAT NAV system. The satellite signal usually comes through the windscreen direct to the unit.
Some (a few) windscreens are reflective and the signal can be degraded. In such cases the supplier will recommend fitting an external aerial.

[dawg_kane]

All satnav units have their own special aerial attached to them called the reciever, this reciever is in direct connection to the satellite system (which is now free to use) and plots exactly where you are in the world by using degrees longtitude and latitude, coupled with the map software inside the satnav unit it can tell exactly where you are at any time.