What is ISO GPS?
GPS is the abbreviation for Geometric Product Specification. This refers to a set of international standards known as the ISO GPS system. These standards define symbols and rules that can be used to unambiguously describe the geometry of components and their permissible deviations through tolerances. Tolerances are defined for dimensions, for form (for example, flatness or roundness) and position (parallelism, perpendicularity, position or symmetry in relation to reference lines) of geometric elements, as well as for their surface roughness. There are also standards for general tolerances.
Some of the standards are intended to describe measurement procedures and measuring instruments for geometric inspection.
Which GPS standards is it essential to be familiar with?
Of the approximately 150 standards in the ISO GPS system, ISO 8015, ISO 1101, ISO 14405-1, the ISO 21920 series comprising three standards, and ISO 22081 are the most important for creating and reading technical drawings.
ISO 8015 sets out 13 principles which must be observed as overarching guidelines for the dimensioning and interpretation of technical drawings.
ISO 1101 defines symbols, terms and rules for form, directional, positional and runout tolerances, often referred to as form and position tolerances.
ISO 14405-1 deals with linear dimensions. It also specifies, for example, the envelope condition and how the tolerance principle based on the envelope condition can be applied to the entire drawing.
Roughness symbols and parameters can be found in ISO 21920, Parts 1 to 3.
A new standard has been in place since 2021 for general tolerances, which had been specified for many years in accordance with ISO 2768. ISO 22081 sets out a new approach to defining general tolerances, which was a key factor in the revision of the IHK examinations.
When was GPS introduced?
Dimensions and position tolerances have been in use for many decades. The fundamental principles underlying today’s ISO GPS system can even be traced back to the ‘true position’ principle, which was developed during the Second World War to describe component geometries and improve their interchangeability.
In 1996, it was decided at international level to further develop existing standards relating to geometric description, tolerancing and measurement for the ISO GPS system within a standards committee. The first fundamental standards were published before 2000.
The publication of ISO 8015 in 2011 marked a decisive step in the introduction of GPS. One of the fundamental principles of this standard stipulates that the ISO GPS system applies to the entire drawing as soon as a symbol or standard from the standard system is used in the drawing. Specifying a fit for a bore or a surface roughness symbol is therefore sufficient in itself to satisfy this principle. Consequently, the GPS rules apply to (almost) all technical drawings from 2011 onwards, even if there is no explicit reference to the standards.
Why is the ISO GPS system important?
Standards represent the state of the art. This is relevant, amongst other things, in relation to product liability, quality requirements and the international comparability of companies. Anyone who does not work in accordance with the state of the art runs the risk that their products will be faulty and unreliable, thereby causing financial damage to the company.
Is GPS relevant to the exams for trainees?
Since spring 2026, the rules of the ISO GPS system have been included in the Chamber of Industry and Commerce’s interim and final examinations for occupations in the metalworking and mechanical engineering sectors, such as machining technicians, toolmakers, industrial mechanics, metal fabricators and precision mechanics, as well as for technical product designers.
Do the general tolerances also include GPS tolerances?
Today’s general tolerances are also based on the ISO GPS system. This replaces earlier, predominantly manufacturing-oriented approaches and focuses consistently on the functional requirements of a component. As a result, ISO GPS is of fundamental importance for the creation and interpretation of any new technical drawing.
Our free guide provides a quick introduction to the ISO GPS system, its technical significance, and its economic and legal background. Mini course!