Patent ID: 7769539
Filing Date: 2010-08-03
Classification: G01C

Abstract:
1. A bearing calculator having a geomagnetic sensor for detecting earth-geomagnetism and a control unit for calculating a geographical bearing based on detection values of the geomagnetic sensor, wherein said control unit can execute a offset error correction processing for correcting offset error to said geomagnetic sensor due to a change of magnetic field in the bearing calculator and, when detection values of said geomagnetic sensor become abnormal state, performs said offset error correction processing if the abnormal state continues for a predetermined time, and does not perform the offset error correction processing if the abnormal state ends within a predetermined time, wherein said geomagnetic sensor detects earth-geomagnetism in a plurality of mutually perpendicular directions, and said control unit does not perform said offset error correction processing if said predetermined time is not required from when at least one of the detection values of the earth-geomagnetism in said plurality of directions becomes a predetermined abnormal state to when all of the detection values of the earth-geomagnetism in said plurality of directions are no longer in said abnormal state, said geomagnetic sensor converts an analog signal of earth-geomagnetism to a digital signal and outputs it as a detection value of the earth-geomagnetism, and said predetermined abnormal state is a state where the detection value of said geomagnetic sensor becomes a maximum value or a minimum value of said digital signal, said calculator is further provided with a display unit, and said control unit calculates a geographical bearing based on detection values of said geomagnetic sensor and controls said display unit to display information of said calculated bearing.