Indra Navia Leading the Evolution Towards Dual-Frequency GBAS

Indra Navia’s ground-based augmentation system (GBAS), developed in Norway, is installed at airports worldwide, enhancing satellite navigation accuracy for aircraft landings. Positioned at or near runways, it provides precise guidance and integrity data, enabling safer, more efficient, and flexible approaches.

The system is currently broadcasting correction and integrity data for GPS only, consistent with the present International Civil Aviation Organization (ICAO) standard. ICAO is now preparing amendments to include Europe’s Galileo constellation in a forthcoming dual-frequency, multi-constellation (DFMC) standard, known as GAST E.

The European Space Agency (ESA)-funded project entitled ‘Category III GBAS with Evolution Toward DFMC’, led by Indra Navia, supports this transition. It is working towards completing implementation of the current GAST D capability, and contributing technical input to the definition of GAST E, focusing on integrating Galileo as a second constellation.

Because GAST D will function as a fallback mode within GAST E, its completion is also an essential prerequisite for DFMC deployment.

From single- to dual-frequency precision

Conventional instrument landing systems are gradually giving way to satellite-based precision navigation. GBAS improves efficiency and flexibility, but single-frequency variants such as GAST C (for CAT I) and GAST D (for CAT III) remain more vulnerable to ionospheric delays, multipath and signal deformation.

Indra Navia’s work establishes the technical foundation for DFMC GBAS, using both GPS and Galileo across two frequencies. Dual-frequency processing increases robustness against signal distortions, enhancing reliability for all-weather, low-visibility operations.

At a recent ESA-hosted event, researchers from Indra Navia explained how they added advanced integrity monitoring capabilities to GBAS, including signal deformation monitoring, code-carrier divergence detection, and excessive pseudorange acceleration analysis.

Through modeling and simulation, the team evaluated dual-frequency performance under varying geometries and fault scenarios, assessing probability of loss of integrity and probability of missed detection. Comparative testing against current GAST D baselines demonstrated clear performance gains in integrity and availability.

Results show that DFMC GBAS markedly improves precision and resilience, meeting ICAO’s most demanding criteria for CAT III operations. By contributing directly to ongoing ICAO standardization, Indra Navia is helping shape the global path toward next-generation GBAS, systems that are multi-constellation, multi-frequency, and interoperable worldwide.

This project was funded under ESA’s NAVISP program, which supports innovation in the Europeans positioning, navigation and timing (PNT) industry.