1. A computer-implemented method for acquiring a movement trajectory of a subject, said method comprising using a processor to perform steps of: photographing a moving subject by means of a camera; collecting a plurality of images of the subject and information on their locations on a camera image frame, and collecting information on the sizes of the plurality of images; and acquiring a movement trajectory of the subject on the basis of the collected information on the locations and the sizes of the plurality of images, wherein the step of acquiring a movement trajectory of the subject comprises uniquely determining one plane related to the movement trajectory of the subject on the basis of the information on the locations of the plurality of images, wherein the step of acquiring a movement trajectory of the subject is performed on the basis of the one plane with reference to a database in which correlations between the sizes of the plurality of images and the movement trajectory of the subject are electronically pre-stored, and wherein the information on the sizes of the plurality of images includes information on the lengths of diameters that the plurality of images of the subject exhibit in a coordinate plane on the camera image frame.