Abstract— According to the ISO Geometrical Product Specification (GPS), position tolerance can be used to specify axis and derived line in 2D technical drawings by using a diameter symbol within a perpendicular datum system. For an axis which is inclined inset of a component surface without diameter symbol in a non-perpendicular datum system in a 3D tolerancing, is not explicit explicated and lack of examples in ISO GPS standards. Moreover, there exists a contraction by using position tolerance for derive line inside of ISO standards. It causes incomprehension, ambiguous interpretations and definition gaps by using the position tolerance in practice. This paper suggests a new approach for establishing a holistic systematology with explicit defined definitions and examples of position tolerance to complete and enhance the ISO standards. This research is based on the analysis of function-oriented physical behavior of axis and derived line of a component on a theoretical level. An improved systematology for a functional explicit definition of position tolerance is formulated which eliminates the deficits of ISO GPS.