“…A typical surface roughness profile. Table 1 The definitions of surface roughness parameters R 3y maximum height of third highest peak to third lowest valley in each cut-off length R 3z mean height from third highest peak to third lowest valley in each cut-off length R a arithmetical average of surface heights or the center line average of surface heights R c correlation distance calculated from the autocorrelation coefficient of surface heights R k kernel roughness depth R ku kurtosis of surface heights R p maximum height of the profile above the mean line within the assessed length R pk reduced peak height R pm average of the maximum height above the mean line in each cut-off length R q root mean square of surface heights R sk skewness of surface heights R t maximum peak to valley height in the assessed length R tm average of peak to valley height in each cut-off length R v maximum depth of the profile below the mean line within the assessed length R vk reduced trough depth R y maximum of peak to valley in all cut-off lengths R z average height difference between five highest peaks and five lowest valleys within each cut-off length S mean spacing of adjacent local peaks S m mean spacing between profile peaks at the mean line E q root mean square measure of spatial wavelength D a arithmetical mean of surface slope D q root mean square of surface slope were measured (Grönqvist, Roine, Korhonen, & Rahikainen, 1990;Harris & Shaw, 1988;Jung & Reidiger, 1982;Manning & Jones, 1994;Manning & Jones, 2001;Manning, Jones, & Bruce, 1990;Manning, Jones, & Bruce, 1991;Manning, Jones, Rowland, & Roff, 1998;Rowland, Jones, & Manning, 1996). In some studies, several surface roughness parameters were used (Kim & Smith, 2000;Kim, Smith, & Nagata, 2001;Lloyd & Stevenson, 1992), but no reason was given to explain why they were chosen.…”