4. Surface finish parameters

4.1 Separation of geometric deviations

The separation of geometric deviations is necessary to quantify each deviation, independently of the others. There are two standardized methods for separating geometric deviations:

• average line method: this involves filtering the primary profile with a bandpass filter. The differentiation of one deviation from the other is made by considering the distances between two peaks (wavelength). The boundary between two geometric gaps is therefore expressed as a length (cutoff wavelength). The filter generates an average line, hence the name average line method;

• pattern method: this involves breaking down the primary profile into patterns using a "pattern recognition" algorithm....