Overview
ISO 5459:2011 - "Geometrical product specifications (GPS) - Geometrical tolerancing - Datums and datum systems" defines the terminology, rules and methodology for indicating and interpreting datums and datum systems in technical product documentation. As a general GPS standard, ISO 5459 clarifies how to establish datum references (the specification operator) and explains concepts such as datum features, associated features and datum targets. The standard does not prescribe verification methods (the verification operator) and refers to ISO 2692 for detailed maximum/least material rules.
Key topics and requirements
- Terminology and definitions: clear definitions for datum, datum feature, associated feature, datum target, single datum, common datum and datum system.
- Datum hierarchy: roles of primary, secondary and tertiary datums in constraining orientation and location.
- Association concepts: how ideal associated features are fitted to real (non-ideal) datum features using an association criterion (objective function) and possible constraints (orientation, location, material, intrinsic characteristics).
- Graphical language: rules for indicating datum features and datum systems on drawings and 3D models, including datum feature indicators, identifiers and datum targets.
- Collection surfaces and invariance classes: treatment of multiple surfaces as a single collection surface and classification of surface invariance (see Annex B) to determine the situation features used to define a datum.
- Annexes and examples: normative and informative annexes provide associations, invariance classes, worked examples, former practices and relationships to the GPS matrix model.
Practical applications and who uses it
ISO 5459 is essential for professionals involved in design, manufacturing and quality assurance who use geometric dimensioning and tolerancing (GD&T) and GPS:
- Design and CAD engineers - to specify datum references in 2D drawings and 3D models for clear functional definition.
- Manufacturing and CAM programmers - to interpret datum systems for fixturing, toolpaths and assembly locators.
- Quality and metrology teams - to plan measurement strategies, datum target placement and interpretation of inspection results.
- Technical drafters and standards specialists - to apply consistent graphical symbols and comply with international documentation practices.
Using ISO 5459 improves clarity of datum definitions, reduces ambiguity in assembly interfaces, and supports accurate inspection and interchangeability across suppliers.
Related standards
Keywords: ISO 5459, datums, datum systems, geometrical tolerancing, GPS, datum feature, datum target, associated feature, geometric product specifications.
Open preview (PDF)Geometrical product specifications (GPS) — Geometrical tolerancing — Datums and datum systems