Abstract: A reckoning system capable of determining a current location with reliability higher than a desired level by employing both the radio reckoning and the self reckoning which compensate for each other. Vehicle-speed sensor and gyroscope provide a first provisional current location of a vehicle. A second provisional current location is provided by correcting the first provisional current location in comparison with road map information stored in a CD-ROM. A third provisional current location is obtained on the basis of information from a GPS receiver. If the second and third provisional current locations are close with each other within a predetermined distance, then the second provisional current location is selected as a conclusive current location. If not, speed and heading of the vehicle derived from the GPS receiver are compared with those derived from the vehicle-speed sensor and the gyroscope, respectively.