In the preferred embodiment, {HEAD ~ reference terrain altitude maps} are converted to {TAIL ~ reference map transformation values} 
In the preferred embodiment , { HEAD ~ reference terrain altitude maps } are converted to { TAIL ~ reference map transformation values }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL