Overview
EN ISO 25178-3:2012 (ISO 25178-3) is part of the GPS (Geometrical Product Specifications) series for areal surface texture. Published by CEN/ISO, this part defines the complete specification operator for surface texture measured by areal methods. It prescribes the operations and unambiguous order needed to specify measurands for scale‑limited surfaces: the type of surface, method of extraction, association method, and filtration.
Key topics and technical requirements
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Complete specification operator
- Defines a full, unambiguous sequence of operations per ISO 17450-2 to specify areal surface texture.
- Ensures repeatable interpretation of surface texture measurands.
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Type of surface (S‑F vs S‑L)
- S‑F surface: includes form (if form error is to be part of the measurand). The evaluation area for S‑F is normally a square; its side may equal the F‑operation nesting index.
- S‑L surface: excludes form; evaluation area sides normally equal the L‑filter nesting index.
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Method of extraction & evaluation area
- The specification must control the evaluation area's size, shape (rectangular/square) and orientation (commonly aligned to nominal geometry).
- Nesting index choices follow standardized series (examples given: 0.1 mm, 0.2 mm, 0.25 mm, 0.5 mm, 0.8 mm, 1.0 mm, 2.0 mm, …).
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Filtration and filters
- Default S‑filter is an areal Gaussian filter; S‑filter cut‑offs follow a defined series (e.g. 0.0005 mm, 0.0008 mm, 0.001 mm, 0.002 mm, …).
- Tables relate F/L/S nesting indices and bandwidth ratios; other annexes give default attribute values and units for parameters.
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Normative references and annexes
- Tied to ISO 25178-2 (terms & parameters), ISO 14406 (extraction), ISO 16610 series (filtration), and ISO 17450 series (GPS concepts).
- Informative annexes include a decision tree, relationships to profile parameters, and the GPS matrix model.
Practical applications and users
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Who uses this standard:
- Metrologists and calibration laboratories
- Quality engineers in manufacturing (automotive, aerospace, precision engineering)
- Surface measurement instrument manufacturers and software developers
- R&D teams working on surface functional performance (friction, wear, sealing)
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Practical value:
- Ensures comparable, unambiguous areal surface texture specifications across suppliers and customers.
- Guides selection of filters, nesting indices, and evaluation-area settings for reliable measurement and reporting.
- Supports traceable conformity assessment and interoperability of measurement software.
Related standards
- ISO 25178-2 - Terms, definitions and surface texture parameters
- ISO 14406 - Extraction rules
- ISO/TS 16610-1 & 16610-21 - Filtration concepts and Gaussian filters
- ISO 17450-1 / -2 - GPS general concepts and specification operator model
Keywords: ISO 25178-3, EN ISO 25178-3:2012, surface texture areal, specification operators, GPS, nesting index, S-filter, L-filter, areal Gaussian filter, extraction, filtration.
