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AV-282 < SYSTEM DESCRIPTION > [BOSE AUDIO WITH NAVIGATION] NAVIGATION SYSTEM MAP–MATCHING Map–matching is a function that repositions the vehicle on the road map when a new location is judged to be the most accurate. This is done by comparing the current vehicle position, calculated by the method described in the position detection principle, with the road map data around the vehicle, read from the map data stored on the HDD. Therefore, the vehicle position may not be corrected after the vehicle is driven over a certain distance or time in which GPS information is hard to receive. In this case, the current-location mark on the display must be corrected manually. CAUTION: The road map data is based on data stored on the HDD. • In map-matching, alternative routes to reach the destination will be shown and prioritized, after the road on which the vehicle is cur- rently driven has been judged and the current-location mark has been repositioned. If there is an error in distance and/or direction, the alternative routes will be shown in different order of priority, and the wrong road can be avoided. If two roads are running in parallel, they are of the same priority. Therefore, the current-location mark may appear on either of them alternately, depending on maneuvering of the steering wheel and configuration of the road. • Map-matching does not function correctly when the road on which the vehicle is driving is new and not recorded on the HDD, or when the road pattern stored in the map data and the actual road pattern are different due to repair. When driving on a road not present in the map, the map-matching function may find another road and position the current-location mark on it. Then, when the correct road is detected, the current- location mark may leap to it. • Effective range for comparing the vehicle position and travel direc- tion calculated by the distance and direction with the road data read from the HDD is limited. Therefore, when there is an exces- sive gap between the current vehicle position and the position on the map, correction by map-matching is not possible. GPS (GLOBAL POSITIONING SYSTEM) GPS (Global Positioning System) has been developed and con- trolled by the US Department of Defense. The system utilizes GPS satellite (NAVSTAR), sending out radio waves while flying on an orbit around the earth at the height of approx. 21,000 km (13,000 miles). The GPS receiver calculates the vehicle's position in three dimen- sions (latitude/longitude/altitude) according to the time lag of the radio waves received from four or more GPS satellites (three-dimen- sional positioning). If radio waves were received only from three GPS satellites, the GPS receiver calculates the vehicle's position in two dimensions (latitude/longitude), utilizing the altitude data calcu- lated previously by using radio waves from four or more GPS satel- lites (two-dimensional positioning). Type Advantage Disadvantage Gyroscope (angular velocity sensor) • Can detect the vehicle's turning angle quite accurately. • Direction errors may accumulate when the ve- hicle is driven for long distances without stop- GPS antenna (GPS information) • Can detect the vehicle's travel direction (North/South/East/West). • Correct direction cannot be detected when the vehicle speed is low. SEL685V SEL686V ALNIA0839GB SEL526V August 2012 2012 Pathfinder |