Ground Based Augmentation System (GBAS)

Cues What is the coverage of the ground based augmentation system? The position service has a range of? What are the two types of services provided by the GBAS?

Notes Employs a local area augmentation system (LAAS) Provides two services - Precision Approach Service - GBAS positioning Service Receives position information from satellites and applies the correction then transmits via VHF Data Broadcast (VDB) using ILS/VOR frequencies 108 - 118 MHz Precision approach using a pseudo broadcast position to the aircraft from the ground. Min GBAS coverage is +/- 35 degrees within 15 nm of the approach path, and +/- 10 degrees from 15 to 20 nm. Positioning service has a range at about 30 km the accuracy decreases the further from the pseudolite the aircraft is A group of pseudolites will increase the accuracy.

Summary The GBAS augmentation system is a service provided by a ground installation, the satellites transmit to the ground based system its position which has been accurately place. The ground beacon asses the error of the satellites and applies a correction to the station, this error is then transmitted to an aircraft to provide and accurate position. The GBAS can be used for CAT II and CAT III approaches with accurate positions. The key advantage is that it can be used for multiple approaches for different runways at an aerodrome.