10. GPS and Cars

You have seen that GPS has many uses for all kinds of occupations. However the most likely place you are going to see it in action is as part of a satellite navigation system fitted inside a car.

The system (often called 'Satnav') shows the position of the car on a moving map display. As the driver makes their way to their destination, the map display updates itself.

Methods to input data into the system.

	Keypad on the system allows you - To type in your destination. Often a post code is enough information - The type of journey you wish to make: shortest or fastest etc - Any intermediate points you wish to get to along the way - hotel etc. - use predictive text to speed up your entry e.g press 'de and it becomes 'Destination' just like text entry on a mobile phone.
	CDROM / DVD / Hard disk / Memory stick

- Holds map data for the region you are in. It can be a less detailed country wide map or a localised map with much more detail.

Touch screen

- the map screen may be touch sensitive, so you can simply point to your destination on the screen.

	Voice - some systems will accept voice commands.
	Mobile phone - some satnav systems may be linked to a mobile phone to download maps and up to date local information such as restaurants, traffic conditions etc.

Methods of output data

	Screen - shows your location within a map of the area
	Voice - the system tells you what to do without you having to take your eyes off the road. e.g 'Turn left at the next junction'
	Heads up display - some systems will project information on to the windscreen so you can see the details without taking your eyes off the road.

 

How Satellite navigation  uses GPS

There are at least 3 GPS satellites overhead. The Satnav antenna receives their signals:

The satnav computer then works out the location of the car by triangulation.

It then shows the position of the car on a map display on the dashboard.

It keeps reading the GPS signals and working out the latest position.