1. An adaptive welding apparatus for guiding a welding torch along a weld groove, comprising: first means for moving a sensing element along a preselected pathway extending across said weld groove, sensing the weld groove cross sectional configuration, and delivering signals in response to the position and confituration of the weld groove cross secton; second means for receiving said signals, determining relative locations of preselected points on said weld groove, and computing a relative location of the center of area of said weld groove cross section; and third means for computing a guidance point as a function of said center of area irrespective of the cross sectional configuration of said weld groove, and controlling the lateral movement of said welding torch in a direction toward said guidance point.