OBSERVER: How EGNOS has revolutionised the way we fly

12 seconds-that's how long it took to make history. On 17 December 1903, two bicycle shop owners from Ohio, USA, Orville and Wilbur Wright, completed the first powered flight of a heavier-than-air aircraft. The flight covered 36 metres at a speed of just under 11 kilometres per hour and lasted only 12 seconds.

Flying has come a long way since then. Over the decades, advances in technology have transformed the way we fly, making air travel safer, more efficient, and more accessible. One technological achievement that has revolutionised air travel is Global Navigation Satellite Systems (GNSS).

GNSS is key for a wide array of applications in today's modern, interconnected world. From everyday tasks such as using maps on smartphones for navigation, to more complex systems involving logistics, emergency services, and infrastructure management, satellite navigation and timing plays an important role. While GNSS such as Galileo and GPS are sufficient for daily commuting, aircraft pilots need a higher level of accuracy, precision, and above all, confidence in the reliability of the signals, known as integrity, to get themselves and their passengers to their destination safely. Enter EGNOS, the European Geostationary Navigation Overlay Service.

In today's Observer, we'll explore how EGNOS works and how it has revolutionised the way we fly.

How EGNOS works

EGNOS is Europe's regional satellite-based augmentation system. It improves the performance of Global Navigation Satellite Systems (GNSS) in Europe and some neighbouring regions and benefits users in many sectors: from captains on board ships, to farmers using their tractors, to pilots landing their planes.

Simply put, EGNOS is a system that improves the accuracy, and more importantly, the integrity of GPS navigation data. At the moment, EGNOS only works with GPS signals, but the upcoming version (EGNOS v3) will also include Galileo support.

Normally, a person's position can be determined using GPS signals from four of the more than 30 GPS satellites currently orbiting Earth. However, GPS receivers, such as those found in smartphones, typically have an accuracy of about five metres in open areas. EGNOS improves this accuracy, allowing receivers to pinpoint locations to within one to two metres.

EGNOS accomplishes this improved accuracy with the help of more than 40 ground stations across Europe that receive GPS signals and forward them to control centres. These centres analyse the data to detect errors in the GPS signals, such as satellite clock errors, ephemeris, and ionospheric delays, and generate correction and integrity information. This information is then sent to uplink stations, which transmit it to geostationary satellites carrying EGNOS payloads. These satellites then relay the corrected signals back to EGNOS-enabled GPS receivers on Earth, combining the corrected GPS signals with the integrity messages to provide users with not only more accurate positions but also crucial assurance on the trustworthiness of those signals. EGNOS also delivers a highly accurate time reference, further supporting critical applications.

EGNOS Services in a nutshell

Through an array of services, EGNOS provides data corrections to many different types of users: the Open Service (OS) for public applications, the EGNOS Data Access Service (EDAS) for professional and commercial access, and the EGNOS Safety of Life (SoL) Service for safety-critical operations. EDAS and OS support day-to-day activities such as personal navigation, surveying, tracking goods, and precision farming. Moreover, the EGNOS Safety of Life Assisted Service for Maritime users (ESMAS) offers tailored support for maritime navigation, while the SoL service remains central for civil aviation, supporting landing procedures such as LPV-200 for precision aircraft approaches, and is also intended for future applications in maritime, rail, and road transport.

The LPV-200 service, in particular, has become a game-changer for aviation by enabling landings equivalent to Category I Instrument Landing System (CAT I ILS) procedures, which allow pilots to land with limited visibility down to a decision height of 200 feet (about 60 metres), but without the costly ground infrastructure.

EGNOS and aviation: the LPV-200 Service

As an aircraft approaches an airport and begins its descent towards land, pilots need to know their precise position relative to the runway.

The Instrument Landing System (ILS) is a traditional ground-based radio navigation system which guides pilots during the final approach to land, providing accurate lateral and vertical guidance. It works through a combination of localiser and glideslope transmitters located around the airport. The localiser aligns the aircraft to the runway centreline, while the glideslope ensures alignment with the correct descent path.

ILS approaches are classified (Category I, II and III) based on the minimum visibility and decision height required for landing. A Category I ILS approach typically requires a decision height of 200 feet (approximately 60 metres) above the runway, at which point the pilot must decide whether to land or execute a missed approach. While ILS is widely used and known for its accuracy, it requires significant ground infrastructure, including antennas and regular maintenance. All of this is costly to install, especially at smaller or remote airports. This is where EGNOS comes in.

EGNOS LPV-200, which stands for "Localizer Performance with Vertical Guidance" is a procedure which provides pilots with lateral and vertical guidance in a similar way to ILS. However, instead of relying on ground-based radio signals, LPV-200 uses EGNOS satellite signals. Because EGNOS improves the accuracy and reliability of GPS, it enables aircraft to follow a precise path comparable to that provided by ILS. With a decision height of 200 feet, LPV-200 enables approaches equivalent to Cat I ILS procedures.

One of the main advantages of the LPV-200 Service is that it relies on satellite technology rather than airport-specific infrastructure. This makes LPV-200 procedures more flexible and cost-effective particularly for airports that may not have the resources to install and maintain an ILS. Since its certification for use in civil aviation in 2011, EGNOS has become an important operational tool for European aviation. Today, EGNOS is used at more than 500 airports improving safety and accessibility.

Fewer manoeuvres, lower costs

These EGNOS-enabled LPV approaches are not only safer, but also more sustainable. The availability of LPV at all airports provides a greater choice of alternative landing sites, which can reduce flight distances, fuel consumption, and emissions.

Thanks to lower decision heights, pilots can more accurately assess landing conditions, often eliminating the need for circling or diverting. Minimising diversions and aborted landings significantly reduce fuel consumption, benefiting both the airline and the environment.

EGNOS and helicopter emergency services

Although EGNOS is of great benefit to commercial flights, the system also provides crucial support to rescue operations by other aircraft types, specifically helicopters. Helicopters play an important role in rescue and Medevac (medical evacuation) operations across Europe. According to the European Union Aviation Safety Agency (EASA), hundreds of helicopters dedicated to emergency medical services operate throughout the European Economic Area (EEA), significantly bolstering rapid critical care and transport efforts; while exact fleet figures fluctuate, EASA's Annual Safety Review highlights the ongoing importance of these rotary-wing aircraft in European air rescue services.

Helicopters have carried out rescues since coming into operational service in the 1950s, but poor weather or low visibility could make reaching remote sites dangerous or even impossible. EGNOS makes it possible to create satellite-guided routes for helicopters into locations like hospitals, mountain valleys, or offshore platforms. These routes provide accurate guidance for pilots, helping rescue and medevac teams reach people in need more safely, even when conditions are difficult.

EGNOS has fundamentally changed the way we navigate the skies, improving the safety, accessibility, and efficiency of aviation across Europe. As we look to the future, EGNOS v3 will augment the performance of both GPS and Galileo signals to provide even more precise and reliable navigation and extend its coverage beyond Europe, benefiting even more users.