In mass metrology, the stability of weights, such as standard kilograms, has always been a major concern. Models have been used to describe the various factors that affect mass stability. Surface quality is one important factor that can include the amount and type of pollution present on the surface. However, another important factor is surface roughness. Methods for determining surface roughness differ in their lateral and height resolution and also by the type of information that each method provides, such as: profile, image of defects, power-spectral-density, surface auto-correlation function, or different statistical parameters such as the root-mean-square (rms) height (or roughness) δ.