Surface Metrology Q&A


The Surface Metrology Q&A is a regular section in Digital Surf's Surface Newsletter that focuses in each issue on a hot topic in surface metrology. Frequent mistakes and misunderstood points are discussed and correct interpretations are given. These sections are a useful complement to the Surface Metrology Guide that offers more in-depth explanations.


Scale-Sensitive Fractal Analysis, or SSFA in short, is a geometrical multi-scale method that makes it possible to explore surface behaviors in a wide range of lateral scales, and identify the active bandwidth with regards to a given function.

Scale-Sensitive Fractal Analysis

Many international standards use the term "default" with a precise meaning. This page explores what "defaults" imply and how to interprete them, not exactly what it may seem to be...

About "Defaults" in standards

This page explores the delicate art of applying micro-roughness filters to a profile or a surface in order to prepare it for analysis. The use of the λs filter on a profile or the S-Filter on a surface is sometimes not well understood.

About λs Filter


How much do you know about surface metrology? This quiz in 10 questions covers topics such as: areal surface texture, areal field parameters and profile parameters. Don't worry, the solution is provided at the end.

Surface Metrology Quiz

Form is a component of surface finish which corresponds to the general shape of the surface. When analyzing surface texture (i.e. waviness and roughness), form should be removed. Find out why and how this operation should be carried out.

Form removal

Are you measuring surface roughness over an area? Ever wondered whether or not it is OK to compare values calculated (Sa, Sq, Sz etc.) with profile surface texture specifications (Ra, Rq, Rz etc.)?

How to compare Ra and Sa?


Depending on the functional role of an engineered surface, all or part of the surface may be taken into consideration when calculating parameters. This page sheds light on this issue and details methods for dealing with it.

About surface function

Surface measurement instruments can be calibrated using physical reference specimens. But how does one go about verifying the accuracy of surface analysis software?

Software verification

Summer is coming, which for some means long, lazy hours spent reading on the beach or by the pool. But why not take a break from the latest bestseller to brush up on your surface metrology skills? Here are some recommendations.

Book on Surface Metrology


The upcoming revision of profile parameter standards is set to change the way metrologists, technicians and engineers perform and analyze measurements. Here is an update of the current work at ISO.

ISO 21920