{HEAD ~ Reference terrain altitude maps} are converted by a reference map transformation to {TAIL ~ data} which correlates the reference map to the altitude of the missile 
are converted to
{ HEAD ~ Reference terrain altitude maps } are converted by a reference map transformation to { TAIL ~ data } which correlates the reference map to the altitude of the missile
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH