Plain English Meaning

These are GPS receivers fixed at known points on the ground at an airport. Because the equipment knows exactly where it is, it can measure how far off the GPS signals are, and that error information is sent to aircraft so their GPS positions become accurate enough for precision landings.

Full Definition

Ground-based GPS receivers, installed at precisely surveyed locations on or near an airport, that form part of a Ground Based Augmentation System (GBAS). Each receiver tracks the GPS satellites in view and compares the satellite-derived position with its own known surveyed position. The differences are used to calculate correction and integrity data, which a GBAS ground station then transmits via to aircraft for use during and .