The Fourier transformed data is filtered by retaining a subset of the Fourier coefficients at {HEAD ~ each} of {TAIL ~ the locations} 
The Fourier transformed data is filtered by retaining a subset of the Fourier coefficients at { HEAD ~ each } of { TAIL ~ the locations }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL