Current vehicle navigation systems are provided with features such as spoken instructions before junctions and branching points and by displaying an enlarged map of junctions to ensure that the driver is able to drive without difficulty along the planned route. If these route instruction features, which are designed to reduce the direction-finding burden on drivers, frequently give erroneous information, they will not achieve their aim. Therefore, a route guidance function requires a high level of accuracy. The degree of accuracy obtainable from the limited input information provided by digital maps was examined, focusing on (1) the need to give instructions at each junction on the route and (2) selection of the correct spoken instruction to change direction. Several issues were resolved with the existing route guidance function and a more accurate navigation system achieved. (A*)
Abstract