The current location of the array may be compared to {HEAD ~ a reference point} to derive at {TAIL ~ trajectory} directing the user to the reference point, such as an originating point 
The current location of the array may be compared to { HEAD ~ a reference point } to derive at { TAIL ~ trajectory } directing the user to the reference point , such as an originating point
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH