Patent ID: 8798925

Claim:
A method of determining an unambiguous heading direction of a vehicle, the method including: determining a heading alignment error being the difference between a Global Navigation Satellite System (GNSS) direction of motion of the vehicle and an unresolved Inertial Measurement Unit (IMU) heading of the vehicle; adjusting the heading alignment error by 180 degrees to be within a predetermined range if the error is outside the predetermined range; adjusting the unresolved IMU heading of the vehicle using the heading alignment error; determining whether the unresolved IMU heading, after heading alignment error adjustment, is substantially in the true direction of the nose of the vehicle or substantially opposite to the true direction of the nose of the vehicle; and calculating an unambiguous heading direction by offsetting the unresolved IMU heading, after heading alignment error adjustment, by 180 degrees if the unresolved IMU heading is substantially opposite to the true direction of the nose of the vehicle.