Definition
A set of precisely surveyed GPS receivers installed at a known location on or near an airport that continuously track GPS satellite signals. They are the ground component of the Local Area Augmentation System (LAAS), comparing the position they calculate from satellite signals against their known surveyed position to detect and measure GPS errors. Those error corrections are then transmitted to arriving aircraft to enable precision approaches.
Plain English
GPS receivers placed at the airport in spots whose exact position is already known. Because the receivers know where they really are, they can spot any small errors in the GPS signals coming from the satellites and pass corrections to landing aircraft so the aircraft's GPS reads more accurately.
Context Anchor
Seen in Local Area Augmentation System discussions, especially when describing how an airport-based system improves GPS guidance for approaches.
Derivation
"Reference" comes from Latin referre, meaning "to carry back" or "to refer to." In surveying and navigation, a reference point is a known, fixed point that other measurements are compared against. These receivers serve that role for GPS: their location is the trusted standard against which satellite-derived positions are checked.
Why Pilots Care
They enable the high accuracy and integrity monitoring required for LAAS precision approaches down to Category I minimums.
Grounding Statement
Picture several fixed GPS units on the airport watching the same satellites as the aircraft, then telling the aircraft how much the satellite-based position needs to be corrected.
Intuition Check
“Reference receivers” are not the GPS receivers in the aircraft. They are fixed ground receivers used as known comparison points for the system.
Example Sentence 1
The LAAS ground station uses several GPS reference receivers spread around the airport to measure satellite signal errors in real time.
Example Sentence 2
By comparing data from multiple GPS reference receivers, the system can detect and exclude a faulty satellite signal before it affects an approach.