1. A system to define the shape and orientation of a body comprising: a computer navigation system; a sensing device capable of generating a series of representations of the body; a tracking device associated with the body in a fixed relation to the body, the tracking device capable of being detected by the computer navigation system to locate the body relative to the computer navigation system; and the computer navigation system having a central processing unit that can process the series of representations and a relative location of the body to the computer navigation system to determine the shape and orientation of the body relative to the tracking device.