Patent ID: 7376527

Claim:
An azimuth measuring device comprising: triaxial earth magnetism detecting means for detecting earth magnetism; output data obtaining means for repeatedly obtaining triaxial output data not smaller than a predetermined number of times, the triaxial output data being obtained from the earth magnetism detecting means at a time when the direction of the earth magnetism detecting means changes in a three dimensional space; reference point estimating means for estimating, using a statistical method, coordinates of a position where variation of distances from a group of triaxial output data obtained by the output data obtaining means is minimum in a three dimensional space in which the triaxial output data are placed by relating the values of the triaxial output data to the direction components of the respective axes, and for setting the coordinates which are estimated to as a reference point; offset information calculating means for calculating offset information of output data from the earth magnetism detecting means based on coordinates of the reference point obtained by the reference point estimating means; and plane determining means for determining whether a group of output data obtained by the output data obtaining means are distributed in the vicinity of a specific plane, wherein when it is determined by the plane determining means that the group of output data are distributed in the vicinity of the specific plane, the coordinates of the reference point are not estimated by the reference point estimating means, or the coordinates of the reference point estimated by the reference point estimating means are deleted.