The method further comprises measuring {HEAD ~ the first and second components} based on the error signal and {TAIL ~ the repeatable component} 
based on
The method further comprises measuring { HEAD ~ the first and second components } based on the error signal and { TAIL ~ the repeatable component }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL