This invention relates to an information system for motor vehicles.
Vehicle information systems have been developed that provide various types of information to operators of those vehicles. In particular, navigation systems have been developed. One type of navigation system, an autonomous navigation system, uses an on-board map, typically stored on a removable medium such as a compact optical disk (e.g., CD-ROM). The navigation system uses the on-board map to plan a route from a starting point to a destination, which is specified by the operator of the vehicle. Updating an autonomous system's map, for example to add or correct information, typically involves replacing the removable medium.
In some navigation systems the operator inputs the desired destination (and the current location, if required by the system) by entering a spelling of the destination. Some systems also allow an operator to select from a stored list of “points of interest,” such as a list of gas stations or restaurants. Once the operator inputs the destination, the system plans a route along the road network to the destination. The route is typically planned to provide a shortest distance or to try to provide the shortest travel time. Once the route is planned, the operator is guided by the system along the route.
Various approaches to route guidance have been used. A particularly simple approach is to provide the operator with a sequence of discrete instructions, for instance, at intersections where the operator must turn from one street onto another. The operator indicates when he or she is ready for the next instruction. For example, the instructions are provided as an audio output, and the operator says “next” when ready for another instruction.
Another approach to route guidance uses a displayed map on which the planned route and the vehicle's location are dynamically displayed. The operator uses the map to decide when and where to turn in order to follow the planned route.
Some guidance approaches are aided by in-vehicle sensors that are used to estimate the location of the vehicle. For instance, a magnetic compass is used to estimate the direction of travel, and a velocity sensor is used to estimate the distance traveled. In addition, the location of the vehicle can be estimated using the Global Positioning System (GPS). In GPS, multiple satellites emit signals that allow an in-vehicle GPS receiver to estimate its absolute location.
Other types of vehicle information systems have also been developed. In some systems, traffic related information, such as traffic advisories, is broadcast to specially equipped in-vehicle radio receivers.