Automatic Estimation of Camera Position in Robot Soccer

On the robot soccer field it is important to know where the camera is positioned to correct for parallax offsets resulting from the height of the robots. This paper demonstrates a novel method of estimating the camera position purely from the image of the robot soccer field. The principle is to back project the parallax resulting from the walls of the field. The lateral position of the camera may be measured with reasonable accuracy (approximately 1 cm error in our case), although the camera height is more sensitive to measurement errors, especially those resulting from specular reflection. The height of the camera was under-estimated by 11% on one field; this corresponds to a position error of less than 1 pixel when correcting a robot positionpsilas parallax anywhere on the field.