Patent ID: 8175840

Claim:
An apparatus for tracking a posture of a moving object in a three-dimensional space having a z-axis facing a reference surface of the moving object, an x-axis perpendicular to the z-axis in a virtual vertical plane including the z-axis, and a y-axis perpendicular to the x-axis in a virtual horizontal plane including the x-axis, the apparatus comprising: a reference surface direction determination unit configured to detect which direction of up, down, left and right the reference surface is facing with the x-axis as an axis of rotation by using a roll angle of the reference surface that is amended according to a variation of a pitch angle of the reference surface from gravity; an x-axis deviation determination unit configured to detect how far an x-axis direction of the moving object is relatively deviated from a magnetic north direction; a sorter configured to sort output data of a terrestrial magnetism sensor; and a posture determination unit configured to determine the posture of the moving object based on how far the x-axis of the moving object is deviated and which direction of up, down, left and right the reference surface is facing in response to detection signals of the reference surface direction determination unit and the x-axis deviation determination unit.