We propose a user localization system that uses invisible markers for wearable augmented reality (AR) in large indoor environments. Wearable AR systems have received a great deal of attention as a new method for displaying location-based information in the real world. For using wearable AR systems, it is necessary to measure the position and orientation of a user using a positioning infrastructure without the undesirable visual effects that arise from merging real and virtual worlds. In

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... , the infrastructure of the localization environment must be constructed easily and cheaply. The proposed system can estimate the position and orientation of a user precisely by affixing wallpapers containing printed invisible markers on ceilings or walls. The user's position and orientation are estimated by recognizing the markers using an infrared camera with infrared LEDs. To construct environments for the localization system, we developed an initialization tool that calibrates the alignment of the markers from photographs taken by flash illumination using a digital still camera.