Patent ID: 7340362

Claim:
An azimuth measurement device comprising: 2- or 3-axis geomagnetism detection means for detecting the geomagnetism; output data acquisition means for acquiring repeatedly a predetermined number of times or more, either the 2-axis output data at the time when the direction of the geomagnetism detection means changes while keeping the 2-axis detecting directions on a predetermined plane, or the 3-axis output data at the time when the direction of the geomagnetism detection means changes in the three-dimensional space; offset information calculation means for determining a reference point either on 2-axis coordinate space composed of the 2-axis output data or on 3-axis coordinate space composed of the 3-axis output data thereby to estimate the coordinates of the reference point so that the dispersion of the distances from the 2- or 3-axis output data group obtained by the output data acquisition means, to the reference point may be minimized, and for calculating the offset information of the output data of the geomagnetism detection means on the basis of the coordinates of the reference point; and reliability information calculation means for obtaining first reliability information relating to the reliability of the offset information calculated by said offset information calculation means, wherein an acceptance threshold value at the time of calculating said offset information is gradually tightened on the basis of the first predetermined number of the recent first reliability information calculated by said reliability information calculation means.