receiving echo signals arising from {HEAD ~ said pulses} being reflected from {TAIL ~ said surface}; and 
reflected from
receiving echo signals arising from { HEAD ~ said pulses } being reflected from { TAIL ~ said surface } ; and
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH