The biggest difference between profile and areal methods is in the filtration used. A profile extracted from anS-L surface or an S-F surface is not mathematically the same as a profile measured according to the surfacetexture profile chain of standards. The latter uses a profile filter (filtration in the traverse direction only, which isorthogonal to the lay) and the former an areal filter (filtration in both the x- and y-directions which may or maynot be related to the lay direction), which can produce very different results even with the ‘same’ filter type andcut-off/nesting index