Accordingly, a relative positioning system 31 may be used to monitor {HEAD ~ the motion} of {TAIL ~ the points} 122 a 122 c 
Accordingly , a relative positioning system 31 may be used to monitor { HEAD ~ the motion } of { TAIL ~ the points } 122 a 122 c
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 OTH OTH OTH OTH