Overview
EN ISO 25178-2:2022 - Geometrical product specifications (GPS) - Surface texture: Areal - Part 2 (ISO 25178-2:2021, corrected 2023-11) defines the terms, definitions and surface texture parameters used when measuring surface topography by areal (3D) methods. Adopted by CEN and superseding the 2012 edition, this standard establishes a common vocabulary and parameter set for areal surface texture/metrology to ensure consistent measurement, analysis and reporting across industries.
Key topics
The standard covers a comprehensive set of parameters and concepts used in areal surface texture analysis, including:
- Fundamental terms and definitions for areal surface measurement and features (normative vocabulary for GPS).
- Field (areal) parameters:
- Height parameters: RMS height, arithmetic mean height, skewness, kurtosis, maximum peak/pit, maximum height.
- Spatial parameters: autocorrelation length, texture aspect ratio, texture direction, dominant wavelength.
- Hybrid parameters: root mean square gradient, developed interfacial area ratio.
- Material ratio functions and derived parameters: areal material ratio, inverse material ratio, material ratio height difference, material/void volumes and probability-based metrics.
- Gradient distribution and multiscale (fractal) methods for scale-dependent analysis.
- Feature parameters for segmentation and characterization of surface features (peaks, pits), including density, curvature, and statistical descriptors.
- Informative annexes covering multiscale methods, stratified surface determination, implementation details and a standards timetable.
Practical applications
EN ISO 25178-2 is intended for anyone applying areal surface texture measurement in:
- Quality control and inspection in manufacturing (precision engineering, automotive, aerospace, medical devices).
- Surface engineering, tribology and coating evaluation where 3D topography affects functionality (friction, wear, sealing).
- Metrology laboratories, instrument and software developers implementing areal measurement algorithms and reporting tools.
- Research and development teams analyzing texture-function relationships using standardized parameters.
Using a harmonized set of surface texture parameters (e.g., RMS height, autocorrelation length, material volume) improves traceability, comparability and communication between suppliers, customers and testing labs.
Related standards
- Part of the ISO 25178 series (surface texture - areal). Users commonly consult adjacent parts of ISO 25178 (e.g., Part 1 for overview and Part 3 for specification operators) and other GPS documents for full metrology workflows and verification practices.
Keywords: EN ISO 25178-2, areal surface texture, surface texture parameters, GPS, areal metrology, autocorrelation length, RMS height, material ratio, multiscale analysis.