Definition
A precisely surveyed GPS receiver, installed at a known fixed location on or near an airport, that continuously tracks GPS satellite signals and compares the calculated position against its true surveyed position to measure GPS errors. Multiple GPS reference receivers feed data to the Local Area Augmentation System (LAAS) ground facility, which uses the differences to generate correction and integrity messages broadcast to landing aircraft.
Plain English
A GPS receiver bolted down at a spot on the airport whose exact location is already known. Because it knows where it really is, it can measure how far off the GPS signals are at that moment, and that measurement is used to correct the GPS readings on incoming aircraft.
Context Anchor
Seen in discussions of airport-based systems that improve GPS guidance for precision approaches near a runway.
Derivation
‘Reference’ comes from the Latin referre, meaning ‘to carry back’ — something used as a fixed point to compare against. The receiver is called a reference receiver because its surveyed position is the trusted reference that everything else is measured against.
Why Pilots Care
The corrections it supplies enable vertically guided approaches with decision altitudes as low as 200 feet, increasing access to airports in low visibility while maintaining the required integrity and continuity for safe landing.
Analogy
It is like checking a bathroom scale with a weight you already know. If the scale says the known weight is wrong, you know how far off the scale is.
Intuition Check
Do not read reference here as a book or a suggestion. In this term, reference means a fixed known point used for comparison.
Example Sentence 1
The LAAS ground facility compares signals from four GPS reference receivers to calculate the correction message sent to arriving aircraft.
Example Sentence 2
Before the approach became available, maintenance confirmed that all three GPS reference receivers were synchronized and reporting healthy status to the ground facility.