Overview
ISO 22432:2011 - part of the Geometrical Product Specifications (GPS) family - defines standardized terms and types of geometrical features used in specification and verification of workpieces. It maps relationships between geometrical features (the “road map”) to enable consistent future standardization for industry and software makers. The standard is primarily a conceptual and terminological reference rather than a prescriptive industrial procedure.
Key topics
- Three “worlds” of geometry: nominal definition (designer’s ideal), specification (designer’s intended representations), and verification (measurement/inspection representations).
- Surface models:
- Nominal surface model - ideal geometry from technical product documentation.
- Skin model - non‑ideal, continuous virtual surface used for specification/verification.
- Discrete surface model - finite-point representation extracted from the skin model.
- Sampled surface model - measurement-derived point set from the real workpiece.
- Feature types and attributes:
- Nominal, real, discrete, sampled features - correspond to the respective surface models.
- Ideal feature - parameterized mathematical feature (shape, situation, skeleton).
- Non-ideal feature - imperfect feature tied to the skin model.
- Feature of size, one‑parameter family, monotonic containment property - definitions used for size-related features (examples: cylinders, toroids, gauge blocks, o‑rings).
- Specification and verification features/operators: links between the features identified in specification and those used in verification (mathematical vs physical operations). The standard references operators and uncertainties as described in ISO/TS 17450-2.
- Cross‑references and annexes: overview diagram, examples of feature links, and relation to the GPS matrix model are provided in normative and informative annexes.
Applications and who uses it
- Standards developers and technical committees - to harmonize GPS terminology and feature relationships across standards.
- Metrology software vendors and CAD/CAM toolmakers - to implement consistent models for feature extraction, verification algorithms, and data interchange.
- Metrology engineers and researchers - as a conceptual framework for linking design intent to measurement procedures (coordinate metrology, gauges, inspection systems).
- Systems integrators and QA specialists - for understanding how nominal, skin, discrete and sampled models relate when specifying tolerances or creating verification workflows.
Note: ISO 22432:2011 is not intended as a direct how‑to for designers in everyday use but as a consistent reference enabling coherent industrial standards and software implementations.
Related standards
Keywords: ISO 22432, Geometrical Product Specifications, GPS, geometrical features, nominal surface model, skin model, discrete surface model, sampled surface model, specification operator, verification operator, feature of size, industrial metrology.
Open preview (PDF)Geometrical product specifications (GPS) — Features utilized in specification and verification