Patent ID: 7210235

Claim:
An apparatus for detecting azimuth and inclination angle of a device, the apparatus having an azimuth sensor for detecting geomagnetism components in a coordinate system fixed to the device and an acceleration sensor for detecting gravitational force components in the coordinate system fixed to the device and adapted to generate final detection values of the azimuth and the inclination angle of the device in a terrestrial coordinate system by use of the geomagnetism components and the gravitational force components, the apparatus further comprising: first computation means for performing coordinate conversion of the geomagnetism components by use of the gravitational force components to thereby obtain the azimuth and the inclination angle to be used as reference data; geomagnetism-depression-angle obtaining means for obtaining a geomagnetism depression angle, which is an angle formed between a horizontal plane and a direction of geomagnetism; second computation means for solving simultaneous equations of the azimuth and the inclination angle, the simultaneous equations being obtained on the basis of the relation between the geomagnetism components in the coordinate system fixed to the device and the geomagnetism components in the terrestrial coordinate system and being specified by the geomagnetism depression angle, to thereby obtain at least one set of computed values of the azimuth and the inclination angle to be used as candidates of the azimuth and the inclination angle; and selection means, operable when a plurality of sets of computed values are obtained, for selecting one set of the computed values among the candidates by referring to the reference data, the selected one set of computed values being used as the final detection values of the azimuth and the inclination angle.