There are no direct datum measurement commands contained in the DMIS language so this article will build on the previous ones by using features we would have already measured or constructed to create them. The reason we create datums, sometimes referred to as coordinate systems, is so that we can report valid feature positions from a known origin in up to three dimensions. The orientation of the coordinate system will also have a direct effect on the shape of some features when analyzed. DMIS’ various datum statements allow us to define the orientation and position of the axes and planes that make up the coordinate system. When you create a datum you use features to define the direction and position of three scales that are square to each other. Each scale comprises an axis that will lie along the direction of the datum feature and a plane that is square to that scale, passing through the scales zero point. Because of their close relationship with CAD systems, DMIS datums are always right handed.