Operator: Filter

The Filter operator is typically used after a surface has been leveled, and before the surface is analyzed for roughness or other parameters in order to remove features from the surface. ProfilmOnline offers two filtering methods, Gaussian and Spline. Both options can output either a roughness or waviness image.

The Gaussian filter averages the surface over a particular area which results in a smaller output image. The size of the excluded region is determined based on the cutoff filter.

The Spline filter does not alter the size of the output image. This filter option is a bit more flexible since along with the the cutoff length, the tension (β) can be adjusted. If β = 0.6252, this will approximate the effect of the Gaussian filter.

The correct cutoff filter to use depends on the expected roughness value. This can be determined by referencing the following table:


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Note that for Profile Parameters a cutoff filter is automatically being applied as part of the ISO and ASME standards. The cutoff filter setting can be changed by clicking on the settings icon in the right-hand panel. With the right cutoff filter being applied, there may be no need for leveling or form removal.
The Areal Parameter calculations do not include a cutoff filter. Here it is important to apply filtering before calculating surface roughness.