Abstract: Consistent with an aspect of the present disclosure, a method of locating a position of a movable member is provided. The movable member is movable along a path and has a surface with a plurality of markings provided thereon. The method includes sensing an image of a portion of the surface of the movable member, and calculating a position of the movable member based on the image. Further, the method includes determining whether the movable member is at a location corresponding to one of the plurality of markings, and eliminating an error associated with the position when the movable member is at the location corresponding to the one of the plurality of markings.