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