Abstract: A system for computer assisted navigation during surgery. At least one processor operates to identify locations of fiducials of a reference element on a ball tip stylus in images obtained from tracking cameras with at least partially overlapping field-of-views imaging the ball tip stylus with a ball palpating a surface of a bone. Operations determine locations of a center of the ball based on the locations of the fiducials of the reference element, and define an offset-acquired surface of the bone based on mathematically connecting the locations of the center of the ball. Operations determine local normal vectors to the offset-acquired surface for the locations of the center of the ball. Operations translate the offset-acquired surface of the bone toward the surface of the bone along the local normal vectors based on a radius of the ball to define an acquired surface of the bone.