Geometric product specification (GPS)

The development of subcontracting, the multiplication of national and international exchanges and the introduction of quality assurance systems have highlighted the need for a common, unambiguous language recognized by all partners to define product specifications.

The ISO/TR 14638 report states:

"GPS (Geometrical Products Specification) consists in defining, through a definition drawing, the shape, dimensions and surface characteristics of a part that ensure its optimum functioning, as well as the dispersion around this optimum for which the function is always satisfied.

The manufacturing process will produce real parts, which are not perfect, with deviations from the optimum on the one hand, and from part to part on the other.

These actual parts will be measured to compare them with the specification.

It is necessary to be able to connect :

• the room imagined by the designer;

• the actual part manufactured ;

• knowledge of the part obtained by measurement.

To enable this relationship to take place and to allow mutual understanding, standards have been developed in the GPS field, covering basic definitions, symbolic representation, measurement principles, etc.".