The system 3, wherein {HEAD ~ the average position} is linearly proportional to {TAIL ~ the average} of the measured phases corresponding to the multiple positions 
The system 3 , wherein { HEAD ~ the average position } is linearly proportional to { TAIL ~ the average } of the measured phases corresponding to the multiple positions
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH