A method of determining the angular orientation of headgear is described. The headgear has tracking points being at least four tracking points, the relative position of the tracking points is calibrated and stored as relative position information, each of the tracking points comprises an infra-red (IR) reflective point. Light reflected from at least some of the tracking points of the headgear is filtered to allow only light in an IR wavelength band to pass. The filtered IR light is imaged to provide a detected image including at least some of the tracking points. At least some of the tracking points in the detected image are identified, and the position of the identified tracking points in the detected image is determined. The angular orientation of the headgear is determined in multiple different angular directions based on the stored relative position information and the position of the identified tracking points.