A method includes setting an exposure time of an image sensor included in a terminal device so that, in an image obtained by capturing a subject by the image sensor, a bright line corresponding to each of a plurality of exposure lines included in the image sensor appears according to a change in luminance of the subject. The method also includes obtaining a bright line image including a plurality of bright lines, obtaining identification information of the subject, and obtaining a direction of light of the subject. Additionally, the method includes calculating a distance between the terminal device and the subject, and obtaining a location of the subject. The method further includes calculating a location of the terminal device using the distance and the location of the subject, and sending the location of the terminal device to a server.