Definition
The lowest published altitude on an airway segment that guarantees both obstacle clearance and acceptable navigation signal coverage when the aircraft is navigating using GPS or WAAS. It applies only to aircraft equipped with approved GPS or WAAS receivers and is shown alongside the conventional MEA on en route low altitude charts.
Plain English
It is the lowest altitude you are allowed to fly on an airway segment if you are using GPS or WAAS to navigate. Below this altitude, the route is not guaranteed to clear terrain or to give reliable satellite-based navigation.
Context Anchor
Seen on IFR en route charts, especially in the chart legend and along route segments where a GPS/WAAS-based minimum altitude is published.
Derivation
MEA stands for Minimum En Route Altitude. GPS refers to the satellite-based Global Positioning System, and WAAS (Wide Area Augmentation System) is an FAA enhancement that improves GPS accuracy and integrity. The combined label simply means 'the MEA that applies when you are navigating by GPS or WAAS.'
Why Pilots Care
It allows WAAS-equipped aircraft to fly lower than the regular MEA for better fuel efficiency and terrain clearance options while maintaining required obstacle protection.
Intuition Check
Do not read GPS/WAAS MEA as just a suggested GPS altitude. It is a published minimum for that route segment when using GPS/WAAS navigation.
Example Sentence 1
Because the airplane was WAAS-equipped, the pilot could descend to the GPS/WAAS MEA of 4,000 feet instead of the standard MEA of 6,500 feet.
Example Sentence 2
With WAAS available, we can descend to the published GPS/WAAS MEA instead of the higher standard MEA.