Horizontal Reference The horizontal reference defines the XC or length direction for a non-cylindrical feature Unigraphics requires horizontal and vertical directions which are independent of the WCS, on the planar placement face. A horizontal reference can be any solid edge, endpoint,datum axis or datum plane that defines a vector parallel to the planar placement face. Shanghai Jiao Tong University 5Shanghai Jiao Tong University 5 Horizontal Reference n The horizontal reference defines the XC or length direction for a non-cylindrical feature . n Unigraphics requires horizontal and vertical directions which are independent of the WCS, on the planar placement face. n A horizontal reference can be any solid edge, endpoint, datum axis or datum plane that defines a vector parallel to the planar placement face