Patent ID: 8548723

Claim:
A car navigation system comprising: a casing; an acceleration sensor for outputting a signal corresponding to acceleration having a sensor detection axis in a back and forth direction of the casing on a horizontal plane; and a processing device programmed to execute a process comprising: estimating, based on the casing being set in the body of a vehicle with a rotation in a yaw direction, a plurality of values of the output signal of the acceleration sensor at a respective plurality of prescribed angles in the yaw direction based on other sensor output signals, subtracting an offset component of the signal from the signal output from the acceleration sensor, comparing the resultant value of the subtraction with the plurality of estimated values corresponding to the respective plurality of prescribed angles, selecting based on the comparisons which of the plurality of estimated values agrees most closely with the resultant value of the subtraction, and determining, as a yaw direction mounted angle of the casing in the body, the prescribed angle that was selected from among the plurality of prescribed angles corresponding to the estimated values as agreeing most closely with the resultant value of the subtraction.