1. A control system for automatically controlling a series of orbital welding bead depositions in a welding gap disposed between a pair of juxtaposed pipe segments, comprising: a welding carriage; a guide arrangeable about the juxtaposed pipe segments for guidably supporting said welding carriage; a drive mechanism for orbitally moving said welding carriage on said guide; a welding torch movably mounted on said welding carriage including a welding current generator; a drive mechanism for moving said welding torch into selected positions with respect to the welding gap; a metal wire feed device mounted on said welding carriage for feeding metal wire to said welding torch; a welding gap profile measurement device for determining a plurality of measured welding gap profiles of the welding gap as the welding carriage travels on said guide, said welding gap profile measurement device producing electrical signals corresponding to said plurality of measured welding gap profiles; an electronic memory device storing a plurality of nominal welding gap profiles, said electronic memory device being adapted for sending electrical signals corresponding to said plurality of nominal welding gap profiles; comparison and processing electrical circuitry electrically connected to said welding gap profile measurement device and said electronic memory device for receiving and comparing said electrical signals corresponding to said plurality of measured welding gap profiles and plurality of nominal welding gap profiles, and said comparison and processing electrical circuitry being operative to process said signals for producing welding control electrical signals, said comparison and processing electrical circuitry being electrically connected to at least one of: said drive mechanism for moving said welding torch; said welding current generator of said welding torch; said metal wire feed device; and said drive mechanism for orbitally moving said welding carriage on said guide, such that said welding control electrical signals control at least one of: the movement of said welding torch with respect to the welding gap; the welding current generated by said welding current generator; the wire feed rate of said metal wire feed device; and the movement of said welding carriage on said guide.