Ground-Based Augmentation System (GBAS) is a satellite navigation technology added to the Global Navigation Satellite System (GNSS) to augment the entire performance. GNSS basically consists of the Global Positioning System (GPS) and the Global’naya Navigatsionnaya Sputnikovaya Sistema (GLONASS). However, due to the ionospheric gradient, the performance of GNSS with GPS and GLONASS only is limited. Four Augmentation Systems are thus added to GNSS, including the Space-Based Augmentation System, Ground-Based Augmentation Systems, Airplane-Based Augmentation Systems, and Ground-Based Regional Augmentation Systems, in order to improve accuracy, integrity, continuity of service, and availability of navigation. Among the four augmentation systems, GBAS is the only one capable of meeting the most stringent operational needs of aviation, e.g. takeoff and landing in low-visibility conditions. Therefore, it has been effectively applied to the support of takeoff and landing operations.

GBAS consists of a ground segment, airborne segment, and space segment. To facilitate the navigational performance augmentation, GABS is used to develop differential corrections for each satellite, and broadcast these corrections to the airborne receiver over a very high frequency (VHF) data broadcast (VDB) signal transmitted in the 108.0-117.975 MHz band. The ground segment consists of three or four reference receivers located on or near an airport property. These receivers track the signals from navigation satellites. By measuring the time of transmission between the GPS satellite and the reference receivers, the distance the signal traveled is determined, correcting the errors of the GPS or GLONASS. The GBAS Ground Facility then provide aircraft with the updated corrections, integrity, and approach path information through the VHF data link.

With the improved accuracy, integrity, continuity of service, and availability of navigation, GBAS is widely used in approach and positioning. For approach, GBAS enables the user to compute an accurate differentially corrected position solution, meanwhile the definition of a reference path is included. Therefore, the airborne equipment on the aircraft can compute guidance information relative to the reference path. For positioning, GBAS enables the user to compute an accurate differential position solution with integrity. And it was believed that the nominal vertical accuracy of the GBAS on the order of 1.5 meter is more than 95%. However, some implications are still unavoidable due to the potential sources of error. These sources include the hardware or software failures in the ground station or satellites, multipath at the ground segment receivers or airborne receiver, large errors in the ephemeris information broadcast by the satellites, residual ionospheric and tropospheric effects, and the deformation of satellite signals at the source.

Furthermore, GBAS can be applied to different operations in the future. It could be used in surface applications to enhance situation awareness on the airport surface through the use of digital airport maps, provide guidance on the airport surface during very low visibility conditions, support surveillance of airplane positions by the air traffic service providers with the use of Automatic Dependent Surveillance-Broadcast (ADS-B), support runway incursion detection systems, and reduce runway occupancy time through optimum runway exiting applications. Also, it could probably used to guide helicopter landings, support disaster relief or rescue operations, and support unmanned aerial vehicles operations.