A method includes setting an exposure time of an image sensor included in a terminal device so that 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 each of the plurality of subjects. The method also includes obtaining a bright line image including a plurality of bright lines corresponding to each of the plurality of subjects, and obtaining a plurality of identification information from the plurality of subjects. The method further includes specifying locations of the plurality of subjects, determining directions of arrival of lights from the plurality of subjects, calculating distances between the terminal device and each of the plurality of subjects using each of the directions of the arrival of lights, and calculating a location of the terminal device using the locations of the plurality of the subjects and the distances.