Sets forth the operational goals and applications@ and recommends standards and test procedures for airborne supplementary navigation equipment (2D and 3D) using Global Positioning System (GPS) inputs in the en route@ terminal@ and approach modes or any combination thereof. A supplemental navigation system may be used as a primary navigation reference in an aircraft when an approved and operational sole means navigation system is available. The report defines performance@ functions@ and features for 2D airborne equipment@ which performs only lateral guidance@ and 3D equipment@ which performs both lateral and vertical guidance. FAA Technical Standard Order (TSO) ?C C129a references this document.