kinnispunkt, lähtejoon ja/või -pind, mis on lähteks mõõtmestamisel, ISO GPS süsteemi poolt identifitseeritud geomeetrilist omadust iseloomustava suuruse tüübi mõõde kategooria, category of type size of geometrical property are identified in the ISO GPS system, some important part of an object—such as a point, line, plane, hole, set of holes, or pair of surfaces—that serves as a reference in defining the geometry of the object and (often) in measuring aspect

tooriku, detaili, sõlme või masina pind, mida kasutatakse neile valitud koordinaadistikus soovitava asendi andmiseks – baseerimiseks (vt baseerimine), a surface on a workpiece that establishes datum - a surface to which dimensions are referred on engineering drawings, and from which measurements are taken in machining or other engineering operations