a positioning system that determines a current location relative to {HEAD ~ the data} representing {TAIL ~ a geographic region}; and 
a positioning system that determines a current location relative to { HEAD ~ the data } representing { TAIL ~ a geographic region } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH