The distance of {TAIL ~ each focus point} from the best fit surface is then calculated and {HEAD ~ the largest distance} is compared to a predetermined value 
The distance of { TAIL ~ each focus point } from the best fit surface is then calculated and { HEAD ~ the largest distance } is compared to a predetermined value
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH