A semiautomatic procedure for measuring changes in position

A technique is described which permits the tracking of an organism or a body part as it moves through a spatial field. The successive spatial positions of the object under consideration are first recorded by motion-picture photography. The image of the developed film-frame is then projected onto a large screen. A grid of wires stands in front of the projection screen. The scorer touches a metal probe to the vertical and horizontal wires nearest the point on the projected image which he wishes to measure. Through diode and relay circuitry, Cartesian coordinates of the point under consideration are recorded on IBM cards.