ground base augmentation system (sat-nav.) (GBAS)

A Ground Based Augmentation System (GBAS) is a precise navigation system with high location-based accuracy for landing approaches at airports. It is ground-based and uses the DGPS system with stationary reference stations. Since the coordinates of the reference stations are known exactly, the correction data for navigation are derived from them.

GBAS systems are satellite navigation augmentation systems used at airports for approach, landing and departure. With such a system, position accuracy can be increased to less than one meter.

GBAS systems use the GPS system and several GBAS ground stations transmitting in the VHF range between 108 MHz and 118 MHz. They transmit control and correction signals, VHF Data Broadcast (VDB), several times per second to the aircraft, which must be equipped with a GBAS receiver and include these correction signals in the navigation data.