Abstract: A position signaling is usable in connection with an image guided surgery system. A plurality of infrared emitters are mounted on a reference object. The reference object is in turn attached to the rocker arm of a head clamp. The head clamp includes a frame and a first head engaging pin secured to one side of the frame. The rocker arm includes two head engaging pins and is movable in relation to the frame. The image guided surgery system uses the signals provided by the infrared emitters to determine and account for movement of the patient's head.