Overview
EN ISO 14638:2015 - Geometrical product specifications (GPS) - Matrix model (ISO 14638:2015) is a fundamental ISO GPS standard that defines the conceptual framework used to organise and relate the suite of ISO GPS standards. It explains the Geometrical Product Specification (GPS) system, describes a matrix model that maps geometrical characteristics to related standards, and provides guidance for structuring and developing ISO GPS documents under the responsibility of ISO/TC 213. CEN adopted this text as EN ISO 14638:2015 without modification.
Key topics
- GPS matrix model: A framework that shows how individual GPS standards relate to geometrical characteristics and to each other.
- Types of ISO GPS standards:
- Fundamental standards
- General standards
- Complementary standards
- Geometrical characteristic categories: Logical grouping of features such as form, orientation, location, run-out and surface texture (profile).
- Chain links (A–G): Descriptive stages that link specification to verification:
- A: Symbols and indications
- B: Feature requirements
- C: Feature properties
- D: Conformance and non-conformance
- E: Measurement
- F: Measurement equipment
- G: Calibration
- Datums: Explanation of how datums are represented in the matrix (datums themselves are not treated as geometrical properties).
- Preparation guidance: Principles and recommendations for drafting ISO GPS standards, including informative annex formats and the aim to avoid ambiguity and conflicts between standards.
- Maintenance and access: The document replaces earlier TR/CR versions and points users to ISO/TC 213 online resources (matrix and standard list) for up-to-date references.
Applications and practical value
- Provides a masterplan for selecting and applying GPS standards when writing technical product specifications (TPS) and technical product documentation (TPD).
- Helps standards developers and technical committees structure new GPS standards consistently.
- Supports designers, metrologists, manufacturing and quality engineers in:
- Identifying which ISO GPS standards apply to a particular geometrical characteristic or verification task.
- Planning measurement strategies and equipment selection (links E–F–G).
- Defining unambiguous feature specifications and conformance criteria.
- Useful for CAD/CAM, procurement teams and contract drafters to ensure consistent geometric specification and verification across supply chains.
Who should use it
- ISO/TC 213 contributors and national standards bodies
- Standards writers and technical committees
- Engineers in metrology, manufacturing, quality assurance, design and inspection
- Technical authors preparing product specifications and drawing standards
Related resources
- ISO/TC 213 online matrix and catalogue for the current list of GPS standards (maintained on the ISO/TC 213 website).
- EN adoption: EN ISO 14638:2015 (CEN members’ national standards).
Keywords: ISO 14638:2015, Geometrical Product Specification, GPS matrix model, ISO/TC 213, datums, feature requirements, measurement, calibration, conformity, surface texture.
