Electronic compass and direction finding method

A direction finding method, comprising:

• a two-dimensional coordinate data detecting step for detecting two components of the Earth's magnetic field vector, which varies with a heading direction θ of a mobile object, as two-dimensional Cartesian coordinate data (X1, Y1), (X2, Y2) . . . (Xi, Yi);
• a direction calculating step for calculating said heading direction θ of said mobile object from said two-dimensional coordinate data (Xi, Yi) detected in said two-dimensional coordinate data detecting step;
• a magnetic field judging step for determining whether the magnetic field is normal or abnormal;
• and
• a correcting step for correcting a center of an azimuth circle plotted by said two-dimensional coordinate data in a turn of said mobile object, when said magnetic field judging step determines that the magnetic field is abnormal,
• said correcting step having:
• a center calculating step for calculating said center of said azimuth circle from at least three of said two-dimensional coordinate data (Xi, Yi);
• and
• a least squares calculating step for calculating said azimuth circle plotted in said turn of said mobile object from a predetermined number of said two-dimensional coordinate data (Xi, Yi), using the least square method,
• said direction calculating step outputting said heading direction θ of said mobile object calculated from said two-dimensional coordinate data (Xi, Yi) when said magnetic field judging step determines that the magnetic field is normal, and calculating and outputting said heading direction θ sequentially by using said center of said azimuth circle corrected in said correction step when said magnetic field judging step determines that the magnetic field is abnormal.