In-car navigation

An automotive navigation system is part of the automobile controls or a third party add-on used to find direction in an automobile. It typically uses a satellite navigation device to get its position data which is then correlated to a position on a road. When directions are needed routing can be calculated. On the fly traffic information can be used to adjust the route.

Dead reckoning using distance data from sensors attached to the drivetrain, a gyroscope and an accelerometer can be used for greater reliability, as GPS signal loss and/or multipath can occur due to urban canyons or tunnels.

Mathematically, automotive navigation is based on the shortest path problem, within graph theory, which examines how to identify the path that best meets some criteria (shortest, cheapest, fastest, etc.) between two points in a large network.

Automotive navigation systems represent a convergence of a number of diverse technologies many of which have been available for many years, but were too costly or inaccessible. Limitations such as batteries, display, and processing power had to be overcome before the product became commercially viable.

The road database is a vector map. Street names or numbers and house numbers, as well as points of interest (waypoints), are encoded as geographic coordinates. This enables users to find a desired destination by street address or as geographic coordinates. (See map database management.)

Map database formats are almost uniformly proprietary, with no industry standards for satellite navigation maps, although some companies are trying to address this with SDAL and Navigation Data Standard (NDS). Map data vendors such as Tele Atlas and Navteq create the base map in a GDF (Geographic Data Files) format, but each electronics manufacturer compiles it in an optimized, usually proprietary manner. GDF is not a CD standard for car navigation systems. GDF is used and converted onto the CD-ROM in the internal format of the navigation system. CDF (CARiN Database Format) is a proprietary navigation map format created by Philips.

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