| 摘要 |
PURPOSE:To perform accurate correction, by providing the second geomagnetism sensor, which corrects the output of a geomagnetism sensor, which is provided at an ordinary position, at a place where the effect of magnetization from a railroad crossing is strong. CONSTITUTION:A geomagnetism sensor 3 is provided at a part D of the body of a vehicle, e.g., a roof, where the effect of the magnetization from a railroad crossing is small. With this sensor as the first geomagnetism sensor, geomagnetism is measured. A second geomagnetism sensor 4 is provided at a part of the body, where the effect of the magnetization from the railroad crossing is strong, e.g., a floor 1a of the body and the like. Based on the detected outputs of the geomagnetism sensors 3 and 4, the amount of the magnetization of the body is obtained based on the difference, and the detected output of the first geomagnetism sensor 3 is corrected.
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