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