a reference plane setting {TAIL ~ section} for setting a virtual reference plane as a reference defining a geometric placement of an arc welding torch relative to a workpiece during a welding operation, based on said plurality of position and {HEAD ~ orientation} data obtained in said data obtaining section 
a reference plane setting { TAIL ~ section } for setting a virtual reference plane as a reference defining a geometric placement of an arc welding torch relative to a workpiece during a welding operation , based on said plurality of position and { HEAD ~ orientation } data obtained in said data obtaining section
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