DIRECTION ARITHMETIC DEVICE

PURPOSE:To display the correct traveling direction, the present position, etc. of a traveling object regardless of the difference of magnetization and declination, by correcting the declination shift that is produced when a traveling object containing a direction arithmetic device having an earth magnetism sensor is shifted toward a region having a different declination. CONSTITUTION:A computer executes a prescribed program when a vehicle containing an earth magnetism sensor 30 is traveling, and an exciting circuit 60 applies the exciting signal to an exciting winding 32 of the sensor 30 on the basis of the constant voltage supplied from a constant voltage circuit 80. The signals corresponding to the angle formed by the winding direction of the output winding and the horizontal component of the earth magnetism are fed to a microcomputer 110 from the 1st and 2nd output windings 33 and 34 of the sensor 30 via an output circuit 70 and an A/D converter 100. A correction switch 90a feeds a signal to the computer 110 to correct an error caused by the magnetization of the car; while a correction switch 90b feeds the declination correcting signal produced with a change of the traveling region to the computer 110. Then the corrected traveling direction of the car is displayed to a direction display 140.