wherein at least three of {HEAD ~ the plurality} of {TAIL ~ sensors} are disposed so as to be substantially uniformly distributed substantially along a closed curve; and a dial including an operator control 
of
wherein at least three of { HEAD ~ the plurality } of { TAIL ~ sensors } are disposed so as to be substantially uniformly distributed substantially along a closed curve ; and a dial including an operator control
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH