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