Patent ID: 8170797

Claim:
A method of estimating a direction of a longitudinal axis of a vehicle with respect to a local geodetic coordinate system, the method comprising: calculating, by a vehicle-condition estimating unit, velocity vectors at two or more mutually-different positions of the vehicle, respectively, by using GPS (Global Positioning System) signals received by two or more GPS antennas located at the mutually different positions of the vehicle; and calculating, by the vehicle-condition estimating unit, the direction of the longitudinal axis of the vehicle in the local geodetic coordinate system by performing a calculation based on a formula of: θ = arctan ⁡ [ - V1_e - V2_e V1_n - V2_n ] , wherein V 1 and V 2 are the velocity vectors, V 1 _e and V 1 _n are respectively components of the velocity vector V 1 in east-west and north-south directions of the local geodetic coordinate system, V 2 _e and V 2 _n are respectively components of the velocity vector V 2 in the east-west and north-south directions of the local geodetic coordinate system, and θ is an angle corresponding to the direction of the longitudinal axis of the vehicle in the local geodetic coordinate system.