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