If the largest distance from {HEAD ~ a focus point} to {TAIL ~ the best fit surface} is larger than the predetermined value, then the virtual slide image is designated as needing a manual inspection and possible re scan 
If the largest distance from { HEAD ~ a focus point } to { TAIL ~ the best fit surface } is larger than the predetermined value , then the virtual slide image is designated as needing a manual inspection and possible re scan
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH