Patent ID: 7474977

Claim:
An azimuth data computing method comprising the steps of: inputting a signal from a geomagnetic sensor to measure a magnetic field which may be mixture of a geomagnetic field and other magnetic field causing a varying offset, thereby successively providing measurement data of the magnetic field; storing the measurement data successively measured from the input signal of the geomagnetic sensor in a storage; periodically calculating an offset value representative of the varying offset at a given time interval based on a plurality of the measurement data stored in the storage, such that a new offset value of the varying offset is calculated at the given time interval after a previous offset value of the varying offset has been calculated; updating the previous offset value based on the new offset value; and correcting the measurement data which is provided after the previous offset value has been updated, according to the updated offset value and computing azimuth data according to the corrected measurement data.