An apparatus for measuring edge features of a work piece includes an optical sensor assembly and a reference device. The reference device includes a contact surface configured to contact a surface of the work piece adjacent to an edge of the work piece and a marked surface including a plurality of markings indicating positions relative to the contact surface. The reference device is configured to be coupled to a portion of the optical sensor assembly such that the optical sensor assembly is positioned to capture an image representing a portion of the marked surface and an edge feature of the work piece.