Definition
A ground-based GPS augmentation system that improves the accuracy, integrity, and availability of GPS signals in the immediate vicinity of an airport, primarily to support precision approach and landing operations. A LAAS ground station at the airport monitors GPS signals, calculates correction data, and broadcasts that data via VHF radio to aircraft within roughly 20–30 nautical miles, allowing them to fly GPS-based precision approaches to that airport. LAAS has since been redesignated as the Ground Based Augmentation System (GBAS).
Plain English
An equipment setup at the airport that listens to GPS satellites, works out the small errors in the satellite signals, and radios corrections to nearby aircraft so their GPS becomes accurate enough for a precision landing approach.
Context Anchor
Seen on instrument approach charts and in aircraft equipment discussions for approaches that use locally corrected GPS guidance.
Derivation
‘Local Area’ signals that the corrections are produced for and used near a specific airport, in contrast to WAAS (Wide Area Augmentation System), which covers a continent. ‘Augmentation’ comes from Latin augmentare, meaning to increase or add to — here, adding correction data on top of the basic GPS signal to make it more accurate.
Why Pilots Care
It allows precision approaches using GPS at airports that lack an ILS, increasing access in low visibility while maintaining safety standards.
Analogy
LAAS is like having a local guide at the airport fine-tune the GPS information before it reaches the airplane, so the guidance is more exact for that specific area.
Intuition Check
Do not think of LAAS as another GPS satellite. It is a local ground-based system that corrects GPS information for aircraft near a specific airport.
Example Sentence 1
Because the airport had a LAAS ground station, we were able to fly a GPS precision approach with vertical guidance.
Example Sentence 2
With LAAS corrections applied, the aircraft maintained the required vertical path during the final approach segment.