Patent ID: 8698503
Filing Date: 2014-04-15
Classification: G01C,G01R,G01V

Abstract:
1. A geomagnetic application device applying earth magnetism using a value of the earth magnetism determined by measurement, the device comprising: a triaxial magnetic sensor orthogonally arranged to detect triaxial components of a geomagnetic vector which vary with movement of the geomagnetic application device or with postural change of the geomagnetic application device, as orthogonal triaxial component data; a measurement point acquiring means for acquiring a predetermined number of geomagnetic vectors using the triaxial magnetic sensor and storing acquired data in a measurement point storage unit; a calibration means for calibrating offset of the triaxial magnetic sensor; and an azimuth calculation means for calculating an azimuth which the geomagnetic application device faces, correcting the geomagnetic vectors based on a calibrated offset value obtained by the calibration means, wherein the calibration means is provided with an offset calculation measurement point selection means for selecting at least six measurement points of the geomagnetic vectors from among a data set stored in the measurement point storage unit by the measurement point acquiring means and storing the selected measurement points in an offset calculation measurement point storage unit, and an offset value calculation means for obtaining coordinates of a center point of an ellipsoidal sphere by solving an equation of an ellipsoidal sphere body based on the at least six measurement points stored in the offset calculation measurement point storage unit and for storing the obtained coordinates in a calibrated offset value storage unit, the offset calculation measurement point selection means is configured to select the measurement points from among the data set stored in the measurement point storage unit so as to include at least six points, the component values of which are maximum or minimum in each of the three orthogonal axes, and the offset value calculation means calculates parameters which define the ellipsoidal sphere as an azimuth sphere, based on the data of the selected measurement points.