Coordinate transformation method, coordinate transformation device, motion analysis method, motion analysis device, and computer program

A computer program for carrying out procedures which comprise:

• acquiring three-dimensional skeletal information of a subject in motion in a first coordinate system comprising a x′ direction, a y′ direction, and a z′ direction, which are mutually orthogonal;
• using the skeletal information to calculate a Y direction being the traveling direction of the subject, a Z direction along the torso of the subject, and a X direction orthogonal to the Y direction and the Z direction;
• and
• transforming the first coordinate system into a second coordinate system comprising the X direction, the Y direction, and the Z direction, and
• thereby acquiring coordinate-transformed skeletal information.

A coordinate transformation device comprising:

• an acquisition unit that acquires three-dimensional skeletal information of a subject in motion in a first coordinate system comprising a x′ direction, a y′ direction, and a z′ direction, which are mutually orthogonal;
• an axial direction calculation unit that, by using the skeletal information, calculates a Y direction being the traveling direction of the subject, a Z direction along the torso of the subject, and a X direction orthogonal to the Y direction and the Z direction;
• and
• a coordinate transformation unit that transforms the first coordinate system into a second coordinate system comprising the X direction, the Y direction, and the Z direction.