A method and apparatus for determining the relative positions of {HEAD ~ a first object} and {TAIL ~ a second object}  
A method and apparatus for determining the relative positions of { HEAD ~ a first object } and { TAIL ~ a second object }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH