CALCULATION OF THE POWER SPECTRAL DENSITY FROM SURFACE PROFILE DATA

The power spectral density (PSD), in its two-dimensional form, has bee n designated as the preferred quantity for specifying surface roughnes s on a draft international drawing standard for surface texture. The c orrect calculation of the one-dimensional PSD from discrete surface pr ofile data is given, and problems in using fast Fourier-transform rout ines that are given in some of the standard reference books are flagge d. The method given here contains the correct normalizing factors. Two ways to reduce the variance of the PSD estimate are suggested. Exampl es are shown of the variance reduction possible in the PSD's.