DIN EN ISO 18391:2017-03

This International Standard is a Geometrical Product Specification (GPS) standard and is to be regarded as a global GPS standard (see ISO 14638). It influences all chain links of all chains of standards. The ISO/GPS Masterplan given in ISO 14638 gives an overview of the ISO/GPS system of which this document is a part. The fundamental rules of ISO/GPS given in ISO 8015 apply to this document and the default decision rules given in ISO 14253-1 apply to specifications made in accordance with this document, unless otherwise indicated. For more detailed information on the relationship of this International standard to other standards and to the GPS matrix model, see Annex A. Geometric features exist in three "worlds": - the world of nominal geometric definition, in which an ideal representation of the future workpiece is defined by the designer; - the world of specification, in which various representations of the future workpiece are measured by the designer; - the world of verification, in which the designer imagines different representations of the future workpiece. It is important to understand the relationship between these three worlds. A GPS specification defines requirements through a geometric feature and a geometric condition. In the world of verification, mathematical operations can be distinguished from physical operations. The physical operations are operations based on physical processes; they are generally mechanical, optical or electromagnetic. Mathematical operations are mathematical observations of the sampling of the workpiece. This consideration is generally achieved by data processing or electronic processing. These specifications, characteristics and conditions generally defined in this International Standard are well-suited to define requirements for rigid components and assemblies, but they can also be applied to non-rigid components and assemblies. Working Committee NA 152-03-02 AA "CEN/ISO Geometrische Produktspezifikation und Prüfung" ("CEN/ISO Geometrical product specifications and verification") at DIN Standards Committee Technical Fundamentals (NATG) is responsible for this standard.