ISO 17450-1:2011

Overview

ISO 17450-1:2011 - "Geometrical product specifications (GPS) - General concepts - Part 1: Model for geometrical specification and verification" defines a formal model and vocabulary for expressing and verifying the geometry of mechanical workpieces. The standard establishes the mathematical basis, general terms and a non‑ambiguous GPS language to be used across design, manufacturing, inspection and CAx systems.

Key topics and technical requirements

• Modeling concepts: distinguishes the nominal model (designer’s perfect geometry) from the non‑ideal surface model / skin model (physical interface of the workpiece).
• Geometrical features: defines feature types such as ideal features (described by parametrized equations) and non‑ideal features; introduces shape, type, nature, invariance class.
• Feature attributes: covers dimensional parameters, skeleton features (zero‑size reduction), situation features (points, lines, planes, helices for location/orientation).
• Features of size: formalizes linear and angular size features and their role in specification (e.g., LMR/MMR concepts).
• Characteristics and operations: classifies intrinsic and situation characteristics, and defines feature operations, evaluation and transformation methods used for verification.
• Specification & verification rules: provides a consistent symbology language, default decision rules, and verification principles to avoid ambiguity in tolerancing and measurement.
• Mathematical and normative support: includes mathematical symbols and definitions, examples of application (e.g., relation to ISO 1101), and comparisons between tolerancing and metrology (see annexes).

Practical applications and users

ISO 17450-1:2011 is intended for professionals who need precise, unambiguous geometric definition and verification workflows:

• Design engineers defining functional geometry and assembly intent.
• Manufacturing engineers specifying tolerances and manufacturing constraints.
• Metrology and quality engineers developing inspection plans and measurement procedures.
• CAD/CAM/CAx system developers and PLM integrators implementing consistent GPS data exchange.
• Standards committees and educators using a common GPS vocabulary across the product lifecycle.

Typical uses include preparing drawings and exchange files with standardized symbology, creating measurement procedures consistent with GPS, and enabling interoperable CAx communication of geometric specifications.

Related standards

• ISO 17450 (this document is Part 1; Part 2 covers basic tenets, operators, uncertainties and ambiguities)
• ISO 1101 (geometrical tolerancing symbology; example applications are included in ISO 17450-1 annexes)
• ISO 8015 and ISO 14253-1 (default rules and decision rules referenced for GPS application)

Keywords: ISO 17450-1:2011, Geometrical product specifications, GPS, geometrical specification and verification, nominal model, non‑ideal surface model, feature of size, skeleton feature, situation feature, invariance class, CAx.