In Virtual Reality, where all scenes are computer-generated images, a vir­ tual world can be explored by flying or steering treadmills without the user’s performing the same physical movements in the real world. In Aug­ mented Reality (AR), a user sees a virtual world as well as a real world. To avoid the misalignment between two worlds, the user’s pose in the real world must be directly related to the user’s pose in the virtual world; AR requires the same amount of movement in both worlds. To apply AR to large-scale applications, wide-area tracking is essential.