Patent ID: 7095424

Claim:
An image display apparatus for calculating correction information to correct measured values of an orientation sensor, said apparatus comprising: an orientation sensor that senses orientation of a viewpoint and outputs measured values of the orientation; a correction unit that corrects the measured values by using correction information; a generation unit that generates a virtual image based on the corrected measured values; a display unit that displays the generated virtual image; and a calculation unit that calculates the correction information, wherein said calculation unit obtains the measured values of said sensor at the point of when the virtual image, which is generated based on predetermined orientation information, is displayed in an appropriate position, generates the correction information from the measured values and the predetermined orientation information, obtains a user's instruction to modify the correction information, according to the displayed virtual image which is generated based on the measured values of the orientation sensor and the correction information, and modifies the generated correction information in response to the user's instruction, wherein said calculation unit modifies the generated correction information to maintain a relationship between a first angle of rotation and a second angle of rotation according to the generated correction information, with the first angle relating to an azimuth at an orientation of said sensor in a vision coordinate system, and the second angle relating to an azimuth at an orientation of a sensor coordinate system in a world coordinate system and wherein, said display unit displays the image with the modified generated correction information.