Overview
EN ISO 16610-21:2025 - part of the ISO 16610 series on Geometrical Product Specifications (GPS) - specifies linear Gaussian filters for the filtration of surface profiles. The standard defines how to separate the large‑scale and small‑scale lateral components of a surface profile so that filtered profiles can be reconstructed without alteration. It updates and supersedes the 2012 edition, adding implementation details and treatment of end effects.
Key topics and technical requirements
- Scope and definitions
- Applies to open, unbounded open and closed surface profiles (including roundness filtration concepts and extensions to generalized closed profiles with re‑entrant features).
- Normative references include ISO 16610‑1, ISO 16610‑20 and ISO/IEC Guide 99.
- Gaussian weighting function and filter equations
- Formal specification of the Gaussian weighting function for profile filtration and the mathematical framework to extract:
- Large‑scale lateral component (filtered low‑frequency content)
- Small‑scale lateral component (filtered high‑frequency content)
- Transmission characteristics
- Defines transmission behaviour; notably a Gaussian filter gives 50% transmission for sinusoidal profiles at the cut‑off wavelength.
- Practical implementation
- Annex A: implementation details for open profiles.
- Annex B: implementation details for closed profiles (including roundness cases).
- Annexes C and D discuss relationships to the filtration matrix model and the GPS matrix model.
- Additional provisions
- Series of nesting index values, filter designation rules, and guidance on handling end effects.
Applications and who uses it
EN ISO 16610‑21:2025 is directly relevant to professionals and organizations involved in surface metrology and quality control:
- Metrologists and calibration labs implementing standardized filtration for profile measurement.
- Manufacturing quality engineers assessing surface roughness and functional surface characteristics.
- Measurement equipment and software developers embedding Gaussian linear profile filters into instruments and analysis tools.
- Design and R&D teams using filtered profiles for component function prediction (e.g., sealing, friction, contact mechanics).
- Roundness and form analysis specialists, since closed‑profile concepts apply to roundness filtration.
Related standards
- ISO 16610‑1 (Overview and basic concepts)
- ISO 16610‑20 (Linear profile filters: basic concepts)
- ISO/IEC Guide 99 (VIM - metrology vocabulary)
- Other parts of the ISO 16610 series and the GPS matrix model (see Annexes C and D)
This standard ensures consistent, traceable application of Gaussian linear profile filters across measurement systems - improving comparability of surface profile data and the robustness of downstream parameters derived from filtered profiles.
