The invention relates to a referencing apparatus for application onto a patient at least partially covered by surgical drapes. The referencing apparatus includes a plurality of locking elements shaped for engagement with the surgical drapes. The surgical drapes are disposed intermediate the plurality of locking elements and a respective plurality of predefined anatomical sites on the patient. The engagement causes a docking system disposed on the referencing apparatus to assume a reference orientation relative to the plurality of predefined anatomical sites.
