Device-free and privacy preserving indoor positioning using infrared retro-reflection imaging

Indoor positioning is a core technology for indoor daily life applications such as elderly care and home automation. This study presents a device-free and privacy preserving indoor positioning method using infrared (IR) cameras and retroreflectors. The proposed method uses IR cameras equipped with IR LEDs to capture retroreflections from markers attached to walls in the environment, and detects a person who passes between the camera and a marker by observing the occlusion. Because our method employs occlusion of markers, it can track a person without attaching tags to the person. Also, our camera device permits us to filter out visible light and thus the appearance of the person is not recorded. Our evaluation in real environments showed that our method achieved an average positioning error of about 0.3 meters.