Augmented GPS (GBAS-ABAS-SBAS) – Ibex Aviation Academy

GBAS-ABAS-SBAS

Augmented or Differential GPS improves the accuracy of GPS to the level of precision approach aid as well as warns in case of GPS failure
Differential GPS could be GBAS, ABAS or SBAS based on the technology employed for augmentation
Ground Based Augmentation System (GBAS) or Local Area Augmentation System (LAAS)
Air Based Augmentation System (ABAS) using Receiver Autonomous Integrity Monitoring (RAIM)
Satellite Based Augmentation System (SBAS) or Wide Area Augmentation System (WAAS)

Ground Based Augmentation System (GBAS) provides a precision approach for a specific runway using a Pseudolite installed on the airfield
GBAS removes Ephemeris and SV Clock Error while reducing Tropospheric and Ionospheric Error
Pseudolite is an equipment is installed on a precise and known location close to the runway
It acts as an aircraft receiver and calculates the difference or error between its own known position with position received from GPS
The error in GPS position is transmitted to aircraft’s GPS receiver that processes this information like that of another satellite
GBAS system is capable of improving accuracy of GPS to the level of CAT 3C Instrument Landing System

Air Based Augmentation System (ABAS) uses Receiver Autonomous Integrity Monitoring (RAIM) in the aircraft’s receiver
RAIM considers position lines from 5 SV instead of usual 4 SV and a Sixth SV is used to remove one position line that is inconsistent with others
Therefore RAIM requires a minimum of 6 Space Vehicles in its view for a fix reducing the size of cocked-hat to improves accuracy

Satellite Based Augmentation System (SBAS) has a Ground based system that monitors the accuracy of satellites in its area
This error information is transmitted to receivers through a Geo Stationary satellite
The receiver processes this information to correct the GPS Position
Satellite Based Augmentation Systems currently available are European EGNOS, Japanese MSAS and Indian GAGAN