| 摘要 |
PURPOSE:To raise an alarm as to the deviation of an earth magnetism azimuth sensor by comparing in a real time an absolute azimuth obtained from the earth magnetism azimuth sensor, and an absolute azimuth conversion angle obtained, based on an azimuth sensor which is not influenced by earth magnetism. CONSTITUTION:An absolute azimuth calculating means 11 calculates an absolute azimuth, based on data from a steering angle sensor 40 which is not influenced by the turbulence of earth magnetism. A¦theta1-theta2¦ calculating means 12 derives an absolute value of a difference between an absolute azimuth theta1 from an earth magnetism azimuth sensor 30 and an absolute azimuth conversion angle theta2 which has been derived by the absolute azimuth calculating means 11. Whether ¦theta1-theta2¦ is below some positive value alpha or not is discriminated by a ¦theta1-theta2¦<=alpha discriminating means 13, and when ¦theta1-theta2¦<=alpha is nor formed, a magnetic alarm means 14 operates. A present place updating means updates the present place, based on the absolute azimuth theta1 from the earth magnetism azimuth sensor 30 and data from a car speed sensor 20. |
