This standard is a fundamental ISO GPS standard. This document (ISO 14638) explains the concept of Geometrical Product Specification (ISO GPS), and provides a framework to illustrate how current and future ISO standards address the requirements of the ISO GPS system. The framework is intended to be of use to users of ISO GPS standards, by illustrating the extent of the scope of the different standards, and showing how they relate to each other. The framework is also used for structuring the development of standards for GPS by technical committee ISO/TC213. The full set of standards comprising the ISO GPS system is listed on the ISO/TC 213 web site at web link to be inserted here. Where relevant standards and documents are available from sources other than ISO/TC 213, these may also be listed, although any such listing does not intend to be complete and exhaustive.