| 摘要 |
<p>In a vehicle-direction measuring apparatus, central coordinate data (x0,y0) located on a circle of magnetism obtained from the X-Y coordinate data (x,y) detected by a terrestrial magnetism sensor are calculated (7) in correspondence with the direction of the road, calculated using map data (10) or by a GPS device (4), and a present declination correction value ( theta 0) each time the direction of the road is obtained. The declination correction value ( theta 0) is automatically updated in such a manner as to decrease the radius of the circle of magnetism. <IMAGE></p> |
