Abstract : This paper describes a true north seeking and attitude estimation method which uses measurements from an
inertial measurement unit. The true north seeking method applies to finding the attitude in north-east-down coordinate frame
relative to true north provides that the inertial measurement unit is stationary in earth fixed coordinate frame. The angular
rate measurement is used both for true north seeking and attitude estimation, and the acceleration is used for true north
seeking. The method is verified through experiments with an inertial measurement unit which is composed of fiber optic
gyroscope and microelectromechanical accelerometer.