A calibration method and apparatus acquires a correction value to correct
position and orientation measured by using a position and orientation
sensor provided on a physical object by measuring position and
orientation of the physical object when a calibration is started,
generating an image of the virtual object existing on a plane on which
the physical object can be moved, and displaying a composite image formed
by superimposing the image of the virtual object on the captured image of
the physical object. Additional features include detecting an instruction
indicating that a predetermined positional relationship between the
physical object and the virtual object is satisfied, providing a second
measuring position and orientation of the physical object when the
instruction is detected, and acquiring the correction value expressed by
parallel movement of the physical object on the plane and rotation of the
physical object about an axis set in the direction perpendicular to the
plane on the basis of the first position and orientation measured and the
second position and orientation measured.