The authors aim to establish the theory necessary for developing the free gyroscopic compass and focus on mainly two points. One is to suggest north-finding principle by the angular velocity of the earth's rotation, and the other is to suggest orthogonal coordinate transformations of the motion rate of the spin axis, which transforms the components of motion rate in the free gyro frame into those in the platform frame and that this transformed rate is, in tum, transformed into the NED(north-east-down} navigation frame. Subsequently, ship's heading is obtained by using the fore-aft and athwartship components of the motion rate of the spin axis in the NED frame. In addition it was found how to solve the transformation matrix necessary for transforming each frame.
1. Introduction
2. North-seeking principle by using the angular velocity of the earth’s rotation
3. Representation of the motion rate of the spin axis in the frames
4. Determination of transformation matrices
5. Algorithmic design of free gyroscopic compass
6. Conclusion
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