{HEAD ~ The displacements} are selected to reduce {TAIL ~ the overall cyclic error contribution} to an average position measurement 
{ HEAD ~ The displacements } are selected to reduce { TAIL ~ the overall cyclic error contribution } to an average position measurement
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH