To make continuable system operation even when the function of a main navigation system or a location system is lowered or lost by recording the sensor data when a transportation means is operating normally and correcting it automatically.

The system comprises an electric circuit including an anti- magnetic sensor, a microprocessor including a memory, and an I/O unit receiving a data from a speed sensor or an accelerometer. The memory includes a software algorithm which measures the heading direction of a transporting means accurately, calibrates a magnetic sensor automatically, and integrating various sensor data to calculate a flywheel position data. Because of the permanent magnetism of the transporting means, readings of two orthogonal magnetic sensors describes a circular pattern which is distorted elliptically by magnetism induced in an easily magnetizable material, e.g. soft iron. When the transporting means rotates in complete circle, eccentric ellipse is corrected by means of two horizontal axis flux gates or the anti-magnetic sensor.