| 摘要 |
PURPOSE:To indicate always a correct azimuth even during the travelling by detecting that the changing scope of the detecting signal of either of two earth magnetic detecting elements exceeds the stable action range, and executing the magnetization correction. CONSTITUTION:The output signal of sensors 3 and 4 is inputted through lines 7 and 9 to detectors 11 and 12, amplified by amplifiers 15 and 16, and thereafter, converted to a digital signal in an A/D converter 17. The converted output signal is read to a CPU 19, operated in accordance with the azimuth arithmetic program stored at a ROM 21 beforehand and displayed at a displaying part 20. When the detecting signal of either of the earth magnetic detections of the sensors 3 and 4 exceeds the stable action range, it is judged that a magnetization quantity is changed during the travelling, and the detecting element output signal of the changed quantity is corrected on the basis of the detecting element output signal of the unchanged quantity. Thus, since the magnetization quantity can be automatically corrected, the correct azimuth can be always indicated.
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