by Mike McNamee Published 01/02/2017
GPS Jargon Buster
Global Positioning System. The glue that holds electronic navigation together. A group of 24 satellites are positioned around the Earth, 12,000 miles up. From any position on Earth you can 'see' four satellites and from these your position may be calculated to an accuracy of 3m and your height to an accuracy of 4.5m. Encryption of the signals limits the accuracy to these values; the US military have the ability to decode the signals to deliver 1m spatial and 3m height resolutions.
When a GPS is first used (or after a system crash) start-up can be delayed while the system 'finds' and locks on to the visible satellites (the same occurs if you take your satnav on a plane with you it takes while to wake up when you get out at the Spanish airport and try to drive away!).
This usually refers to in-car navigation systems which can plot a route between the current location and a specified destination, offering alternative routes for speed, distance and even avoiding congested areas.
For the destination and for journey planning it is usual to use either a post code or a 'town/street name/house number' input. All in-car systems provide audible instructions for direction changes.
The system built in to a satnav or GPS device enabling optimum routes to be suggested. This is usually carried out on a computer using a map and the mouse to pinpoint the start, and finish along with manual control of the way points, where needed. Auto-routing often has algorithms which seek paths and roads for particular reasons such as:
Using fastest and most direct roads.
Minimising the distance travelled avoiding main roads if the distance is shorter on minor roads.
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