A novel system, based on two video cameras, is developed to quantify the position of a moving subject. Human operators will track the subject with cameras that rotate. The innovative feature of the system is its ability to record the pan and tilt directions of each camera as the cameras are moved. The direction angles are measured by optical shaft encoders and stored on the image at video frame rates in bar code format. These angles and the pixel coordinates of the subject in the video images will be used to calculate the position of the subject in three-dimensional space. The data gathered will establish the feasibility of building a portable video camera system to study animal locomotion out of doors.