Compass sensor unit and portable electronic device

A compass sensor unit having a geomagnetic sensor comprising:

• a magnetic field measuring section that inputs a signal from the geomagnetic sensor to measure a magnetic field which may be a mixture of a geomagnetic field and other magnetic field causing an offset, thereby providing measurement data of the magnetic field, which is represented by a set of coordinate components corresponding to a set of different axes of a given coordinates system;
• a measurement data storing section that has a storage and that stores the measurement data in the storage
• an offset calculating section that calculates an offset value of the offset based on a plurality of the stored measurement data;
• an offset controlling section operative when the offset value is greater than a predetermined critical value for controlling the measurement data storing section to store the measurement data while removing the offset value from each measurement data successively measured from the inputted signal;
• an offset setting section operative when the offset value is smaller than the predetermined critical value for updating a previous offset value according to the offset value;
• a computing section that removes the offset value updated by the offset setting section from the measurement data which is provided after the previous offset value has been updated, to compute corrected measurement data;
• and
• an azimuth measuring section that computes azimuth data according to the corrected measurement data.

A recording medium for use in an electronic apparatus having a processor, a storage and a geomagnetic sensor, the recording medium containing program instructions executable by the processor for causing the electronic apparatus to perform a method of computing azimuth data comprising:

• inputting a signal from the geomagnetic sensor to measure a magnetic field which may be a mixture of a geomagnetic field and other magnetic field causing an offset, thereby providing measurement data of the magnetic field, which is represented by a set of coordinate components corresponding to a set of different axes of a given coordinates space;
• storing the measurement data in the storage;
• calculating an offset value of the offset based on a plurality of the stored measurement data;
• when the offset value is greater than a predetermined critical value, returning to the step of storing the measurement data while removing the offset value from each measurement data successively measured from the inputted signal;
• when the offset value is smaller than the predetermined critical value, updating a previous offset value according to the 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 the azimuth data according to the corrected measurement data.