NAS Implementation - Procedures - GPS Overlay
GPS Overlay Instrument Approach Procedures (IAPs) were the result of an FAA initiative in the 1990s to add "or GPS" to the name of an already existing VOR, VOR/DME, VOR/DME RNAV or NDB approach. The designation allowed the use of certified GPS receivers to fly the approach rather than relying on the VOR, VOR/DME or NDB signal.
"GPS overlay approaches are predicated upon the design criteria of the ground-based NAVAID used as the basis of the approach." (Aeronautical Information Manual (AIM) , section 1-1-19).
GPS Overlay IAPs are being phased out and replaced by newer types of approach procedures.
Example: VOR/DME RNAV or GPS Rwy 16 at Amelia Earhart, Atchinson, KS (K59)