On-board vehicle position detector

Claim 1

A vehicle position detector mounted on a vehicle, comprising: GPS receiver means for receiving GPS signals from GPS satellites and for determining at a predetermined cycle a current position of the vehicle on the basis of said GPS signals received from the GPS satellites; dead reckoning position detector means for determining a current position of the vehicle at a predetermined cycle on the basis of data obtained by sensors mounted on the vehicle; first memory means for storing position data obtained by the GPS receiver means; second memory means for storing position data obtained by the dead reckoning position detector means; comparator means for comparing, exclusively, a position of the vehicle as determined by the GPS receiver means at a current determination cycle with a position of the vehicle as determined by the GPS receiver means at an immediately preceding determination cycle, said comparator means calculating a distance between the position of the vehicle determined at the current determination cycle and the position of the vehicle determined at the immediately preceding determination cycle; and switcher means for switching a present output of the vehicle position detector esclusively in accordance with a result of said comparison by the comparator means, wherein said switcher means selects as the present output of the vehicle position detector a position obtained by the dead reckoning position detector means when said distance exceeds a predetermined reference value, said comparator means otherwise selecting a position obtained by the GPS receiver means.