Ground-Based Augmentation System

Ground-Based Augmentation System

Ground-based augmentation system is basically a satellite navigation program. The idea of this system is that the pseudo range estimates performed by the receivers on the ground are utilized to make varying corrections for satellites. The corrections are given to the receiver on the air through a data link. The receiver on the air will use these corrections to come up with a set of accurate pseudo ranges which will become the basis of solution. The principle is that for a limited baseline gap between the receivers on the air and on the ground, possible errors can be detected immediately by both parties. Thus, these significant errors can be prevented and eliminated by distinctive processing.

Ground-based augmentation system(indra navia) is composed of three to four reference receivers which can be seen near the airport area. These receivers can detect the signals from the satellites used in navigation and then submit the pseudo range calculations and other pertinent information to command system and health performance monitoring to a main processing facility. This main facility will utilize different observations of the pseudo ranges.

From a technical point of view, GBAS can make use of GLONASS or GPS to use differential corrections. The International Civil Aviation Organization Standards and Recommended Practices include GLONASS and GPS altogether.

Installations of GBAS will provide many types of services for various operations; this is for the corrections of GNSS L1 alone. The DCPS or Differentially Corrected Positioning Service is meant to be of generic service for top accuracy positioning. Two GBAS system service have been made. GBAS Approach service Type C (GAST-C) which allows Category 1 process and this is already being used. GAST-D is still being developed and this one will help polish landings and process down to CAT II/III once approved. To eliminate any hazards, GAST-D will steel need extra broadcast messages.

VDB or VHF Data Broadcast is meant to communicate to approaching aircraft using binary GBAS messages. The messages operate in VHF band of 108.025 to 117.975 MHz and it also utilizes time division multiple access or TDMA to let multiple operation of GBAS ground stations on a single frequency.

GBAS (GBAS ground based augmentation system) advanced operations can minimize runway occupancy times and reduce the danger of wake vortex problems because of misplaced runway thresholds. It could maximize runway throughput even in low visibility conditions and worse weather conditions by minimizing space support. It can also lower noise concerns within airport vicinity using GBAS glide slopes and curved approaches.