The GPS Aided GEO Augmented Navigation (GAGAN) is India’s Satellite-Based Augmentation System (SBAS).  It is designed to enhance GPS performance and enable precision approach and landing capabilities across the region.

GAGAN supports all phases of flight and provides an Approach with Vertical Guidance (APV-1) landing capability across the Indian landmass. It also enables Request Navigation Performance (RNP 0.1) En-route operations within India’s Fly Information Region (FIR), with the potential to expand into neighboring FIRs.

Enabling precision landing and air traffic efficiency

GAGAN enhances GPS signal accuracy by:

  • Monitoring satellite signal performance
  • Calculating positioning errors
  • Transmitting augmentation data to SBAS/GAGAN receivers

This results in:

  • Increased accuracy, reliability, and integrity of position estimates for all phases of flight
  • Improved operations in challenging terrain and adverse weather conditions
  • Expanded access to precision landing at airports without ground-based navigation systems

Beyond aviation, GAGAN’s GPS signal corrections benefit non-aviation SBAS-capable receivers by enabling precise positioning and navigation across various sectors, including agriculture, surveying, railways, maritime navigation, and more.

Development of GAGAN for precision navigation

GAGAN was developed in collaboration with:

  • Airports Authority of India (AAI)
  • Indian Space Research Organization (ISRO)

Collins Aerospace is a critical player, leveraging its Wide Area Augmentation System (WAAS) Localizer Performance with Vertical (LPV) guidance software baseline developed for U.S. aviation authorities and adapting it for GAGAN with configuration changes and the development of new ionospheric algorithms suited to the equatorial region.

Development of GAGAN began in 2004, and the system became fully operational in 2013.  GAGAN was subsequently certified for APV-1 operations on April 21, 2015.

System enhancements and innovation

Following its operational certification, GAGAN has continued to evolve with several system enhancements.

  • Addition of a third geostationary satellite to improve redundancy and coverage
  • Introduction of the GAGAN Message Service (GAMS) to enable a national broadcast alert and early warnings
  • Updated GAGAN reference station receivers to support modern GPS L5 signals, preparing the system for future dual-frequency GAGAN enhancements

These enhancements ensure continued performance and scalability for future aviation needs.

The future of GAGAN: dual-frequency navigation

With the full GPS modern L5 signal constellation expected to be available around 2027, Collins and AAI are actively planning to introduce GAGAN dual-frequency service while maintaining the single-frequency service. This dual-frequency service will further enhance system accuracy, availability, continuity, and integrity for users equipped with dual-frequency receivers.

The introduction of dual-frequency service will significantly improve GAGAN performance, particularly during periods of severe ionospheric disturbances such as solar storms, thereby improving overall system availability and robustness.

Achievements

GAGAN represents a significant technological milestone, addressing the unique challenges of the equatorial region, which is prone to ionospheric disturbances that can adversely affect GPS performance.

  • The world's first SBAS certified for Approach with Vertical Guidance (APV-1) operations in the equatorial region
  • The third to globally achieve APV-1 service following the U.S. Wide Area Augmentation System (WAAS) and the European Geostationary Navigation Overlay Service (EGNOS).

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