Definition
A precisely surveyed ground station within a Local Area Augmentation System (LAAS) that receives GPS satellite signals, compares them against its known fixed location, calculates correction data, and transmits that data to aircraft to improve navigation accuracy and integrity for precision approaches.
Plain English
A ground station near an airport whose exact position is already known. Because it knows where it is, it can measure the small errors in GPS signals and send corrections to nearby aircraft so their GPS readings become much more accurate.
Context Anchor
Seen in discussions of LAAS, where airport-based equipment improves GPS accuracy for precision approach operations.
Derivation
"Reference" comes from the Latin referre, meaning "to carry back" — to point back to a known standard. The facility is called a reference because its surveyed position is the trusted standard against which raw GPS signals are checked.
Why Pilots Care
It supplies real-time corrections that allow GPS approaches with accuracy comparable to ILS, increasing access to precision landing capability at more airports.
Intuition Check
Do not read “reference” as a book or a general mention of something. Here it means a known, fixed location used as the basis for correcting GPS position information.
Example Sentence 1
The LAAS installation at the airport uses several GPS-reference facilities positioned around the field to generate correction data.
Example Sentence 2
Before beginning the LAAS approach, the pilot confirmed that the GPS-reference facility was operational and providing valid corrections.