14. Peaks, Valleys, and Skewness


Many of our surfaces have symmetric peaks and valleys that follow a normal or bell-shaped height distribution. But often we may want that distribution to be stretched, or skewed, toward the peaks or valleys.

The Rsk parameter, which is widely used to report this skewness, has some serious issues baked into the math which can lead to incorrect conclusions. In this video we examine the Rsk parameter, how it’s calculated, and why it can be unstable. We also provide alternative parameters that may be better than Rsk for production measurement.