Abstract: A navigation system having two sensors and two circuits. A travel sensor sends a pulse whenever a vehicle travels a predetermined distance. An angular velocity sensor outputs a voltage corresponding to an angular velocity of the vehicle. A correction circuit calculates the angular velocity from both a reference voltage that corresponds to an angular velocity of zero and an output voltage from the angular velocity sensor. A reference voltage resetting circuit monitors the pulse from the travel sensor; sets, as an effective sampling interval, at least a part of a interval from the end of a predetermined first cancellation interval after the pulse stops until the start of a second cancellation interval prior to a resumption of the pulse; calculates an average value of the output voltage of the angular velocity sensor, which has been periodically sampled during the effective sampling interval; and resets the reference voltage to the average value.