A number of reports have been published in recent years concerning research work that is underway in Europe. America and Japan on navigation systems for vehicles. The systems reported on to date employ a variety of position detection sensors, such as geomagnetic sensors, gyrocompasses and loran receivers. However, the literature contains virtually no reports of automobile navigation systems that make use of a Global Positioning System (GPS) as a means of detecting and determining the location a vehicle.The authors have developed a GPS automobile navigation system that is intended to be one subsystem of a cinorehensive on-board information system. The total system incorporates car telephone data communication capabilities as well as various functions for centralized operation of the vehicle equipment.This navigation system can accurately locate a vehicle's position using position data received from GPS satellites together with data supplied by geomagnetic sensors. In additions, map data stored in a CD-ROM can be called up for display on a monitor to indicate the vehicle's position on a map.This paper describes the system and presents the experimental results for position detection accuracy, as well as the author's observations on map data standardisation.