Patent ID: 7363147

Claim:
A navigation device in a vehicle including a distance sensor for detecting a travel distance of the vehicle, the navigation device comprising: an acceleration sensor that generates outputs of accelerations in a front-rear, a lateral, and a vertical directions of the acceleration sensor; and a correction unit that detects a first group of outputs of the acceleration sensor with respect to the three directions, the first group including information on an orientation of the acceleration sensor relative to the vehicle, memorizes the first group as reference orientation values, corrects the memorized reference orientation values with respect to the three directions, based on three averages of outputs generated by the acceleration sensor while the vehicle travels after the first group are generated, each average being an average of outputs with respect to each of the three directions, determines an orientation of the vehicle when the vehicle travels, based on (i) the corrected reference orientation values and (ii) a second group of outputs of the acceleration sensor with respect to the three directions, and corrects a travel distance detected by the distance sensor, based on the determined orientation of the vehicle.