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EASE: EGNOS Aviation Services Evolution


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The EASE project examined possible evolutions of the EGNOS programme for safer and more efficient aviation beyond 2025. It investigated enlarging the provision of EGNOS services to communication navigation surveillance and air traffic management, providing additional features to increase robustness against potential threats, and enhancing the navigation, positioning and/or timing provided to users.

Contract Number: Call for Tenders No 631/PP/GRO/RCH/17/9876

Project Segment: Horizon 2020, EGNOS Mission and Services evolution

Duration: 12 months (April 2018 – April 2019)

Budget: €300 000

Project Partners: Egis Avia, Helios, and Thales Alenia Space

Project Coordinator: 
Anne Cloerec (Egis Avia) 

European Commission Project Manager:
Ignacio Alcantarilla-Medina

GSA Project Manager:
Pierre Durel


The European Commission is defining the long-term evolution of the EGNOS programme beyond the current EGNOS Service Release V3. These evolutions will support the implementation of safer and more efficient aviation operations. In this sense, the evolution of EGNOS services for aviation safety beyond 2025 could take any of the following three directions:

  • enlarge the provision of EGNOS services to communication navigation surveillance (CNS) and air traffic management (ATM) beyond navigation, notably to address surveillance (ADS-B) and possibly support timing services for communication systems
  • provide additional features to improve robustness against external intentional or unintentional threats/attacks to the EGNOS navigation service, for instance by adding authentication to GNSS signals or ad hoc features at antenna and receiver level
  • enhance the navigation, positioning and/or timing performance provided at user level, for instance by improving the vertical position accuracy and the time-to-alert to enable support for Cat II approach procedures

Project objectives

The project aimed to support the roadmap definition for the long-term evolution of the EGNOS programme.  The objective was to identify possible new services that would benefits from EGNOS V3 and beyond, analyse and define the reasons motivating evolutions along these services, determine associated constraints and pre-requisites, and assess the added value for users.


Future applications

Through consultation of the European ATM community, the project identified future applications that would benefit from EGNOS V3 services. These applications are:

  • enhanced advanced surface movement guidance and control system (A-SMGCS) application: automatic dependent surveillance broadcast (ADS-B) is used to enhance the surveillance quality (by providing additional surveillance means) at airports already equipped with A-SMGCS. This solution allows for the improvement of A-SMGCS alerts, as well as a routing function (e.g. follow the green function). It may also enable the implementation of additional alerts.
  • alternative A-SMGCS applications: ADS-B is used to provide an alternative means of “A-SMGCS like” surveillance, i.e. an A-SMGCS with a possibly reduced number of alerts or functions.
  • SURF-IA (enhanced traffic situational awareness on the airport surface with indications and alerts): this consists of providing flight crew with information on the airport moving map display, as well as indications and alerts (auditory and on devices) about situations where a collision hazard exists or a collision appears imminent.
  • SURF-A, which consists of providing alerts to the pilot with respect to surrounding traffic during runway operations to prevent collision on the runway. SURF-A is similar to SURF-IA but does not include the use of a cockpit display of traffic information (CDTI) and the provision of indication.
  • EGNOS vertical reference service: EGNOS is used as a new altitude reference system; geodetic altitude is used instead of barometric pressure measurements to calculate altitude. Special Authorisation (SA) CAT I approaches are introduced to extend the instrument segment of a CAT I approach to allow CAT I operations down to a decision height (DH) of 150 ft, subject to specific approval from the relevant authority.
  • CAT II operations equivalent to current CAT II operations.

Satellite based augmentation system authentication service for aviation

In addition, the project carried out an assessment of the constraints to implementing a satellite-based augmentation system (SBAS) authentication service for aviation.

Consolidated SBAS requirements

No explicit requirements in terms of accuracy, integrity or availability were defined for the ADS-B surveillance source for alternative or enhanced A-SMGCS applications. Consequently, tentative ones (e.g. for accuracy) were proposed based on a comparison with other means of surveillance. For SURF-IA, ADS-B requirements were defined according to the Radio Technical Commission for Aeronautics (RTCA) standard. For SURF-A, ADS-B requirements were proposed by the manufacturer as part of the SESAR project. So far, the most stringent requirements concerned position accuracy for which a navigation accuracy category for position (NACp) equal to 10 or 11 would be required, i.e. an accuracy of < 10 m or 3 m. For the EGNOS vertical reference service, a set of requirements were proposed based on stakeholder consultations. Lastly, Egis Avia proposed accuracy requirements for SA CAT I obtained by the linearisation of instrument landing system (ILS) CAT I performance at a DH of 150 ft, and horizontal and vertical alert limit (HAL/VAL) requirements derived by scaling the accuracy by a factor of 2.5. The presented CAT II requirements are based on equivalency of ILS CAT II requirements for information purposes only. However, the project recommended the derivation of SBAS CAT II requirements considering SBAS characteristics and their integration within the aircraft.

Safety analysis

The preliminary safety analyses conducted (both for the use of the same source of position for navigation and surveillance, and on beyond CAT I operations) indicated that the use of EGNOS for future services will have a major impact on the EGNOS V3 system, specifically on ground system and receivers which are already DAL B certified. Concerning the authentication service, the use of authentication may increase the likelihood of a loss of EGNOS service. An SBAS authentication scheme should be designed to limit this possibility. Moreover, the authentication function would need to be designed in a way that ensures high levels of availability and continuity (since it contributes to the loss of EGNOS service).

Service provision

The new services (EGNOS-enabled ADS-B services and the vertical reference service) could be categorised as a constituent service for navigation and there would be no need to have a different service provider. Similarly, for the authentication service, no specific advantage has been identified for using an operator different from the SBAS one. 
The provision of the new services would oblige the EGNOS Service Provider (ESP) to complete a safety assessment for the functional change but it would not require them to set up new processes for safety oversight and safety performance monitoring. It may be necessary to define specific service level(s) (SL) of the EGNOS Safety of Life service for the new services, but this would need to be confirmed by airworthiness authorities and the EGNOS service provider.

Cost-benefit analysis

For ADS-B operations and beyond CAT I operations, the benefits were calculated per segment looking at small, medium and large/very large airports, the average number of takeoffs and landings at these airports, and the typical type of aircraft at these airports. The benefits associated with A-SMGCS applications were quantified based on:

  • fuel savings resulting from taxi time optimisation for airspace users
  • safety benefits associated with the continuity of revenue for air navigation service providers (ANSPs) thanks to a lower likelihood of discontinuity of airport activities

Benefits for both SA CAT I and SBAS CAT II services were quantified based on:

  • a reduction in revenue loss due to the capacity gained during adverse weather conditions for ANSPs 
  • a reduction in delay and diversion costs for airspace users

For the vertical reference service, the benefits were quantified for the European Civil Aviation Conference (ECAC) traffic and aircraft fleet only. They were made in terms of fuel savings for airspace users and increased capacity for ANSPs, making a distinction between oceanic and continental traffic.

Further information is available in the EASE project final report

Expected impact

Enhanced A-SMGCS operations

The implementation of the enhanced A-SMGCS solution will be very beneficial for large and very large airports as it is expected to increase the taxi time optimisation by 3% compared to current performance. This is estimated to save up to €573 000 per year in taxi time costs for a large airport. This is very profitable when compared to the initial investment of €200 000 euros for the data fusion element. For medium-sized airports, the return on investment is lower and more than three years of operations would be required to break even.

Alternative A-SMGCS

For the implementation of alternative A-SMGCS for medium-sized airports, the taxi time improvement benefits are not sufficient to balance the implementation costs. Rather, a return on investment would occur instantly if a major incident impacting 50% of operations is avoided thanks to the implementation. Such an event is expected to cost around €6 million in delay and cancelation costs for airspace users. The alternative A-SMGCS solution for small airports would not be profitable unless it prevents two major incidents that each block 100% of the airport’s operations for a day. Nevertheless, the solution could allow small airports to gain a competitive advantage against other regional airports. This is especially the case for airlines that have not implemented SURF-A and SURF-IA services.

The breakeven point was mainly calculated from the perspective of airspace users and not from the perspective of ANSPs.


The added value of the situational awareness SURF A/ IA applications would be relatively small and difficult to assess at airports which are already equipped with A-SMGCS (enhanced or alternative). In addition, the efficiency of these applications relies on the rate of equipped aircraft with ADS-B Out (Automatic dependent surveillance - broadcast), which will be mandatory for specific aircraft categories by 2020 (but not for all aircraft). However, most of the aircraft not affected by this regulation are general aviation aircraft and usually fly to small airports. These airports would receive the least benefits from the ASMGCS category, and would therefore be where SURF-IA could be relevant.

Vertical reference service

There are qualitative and quantitative potential benefits that would both support air traffic growth and contribute to the safety of operations and the improvement of cost-efficiency. A sufficient number of incentives are required to obtain the financial backing of stakeholders however.

SBAS SA CAT I operations

The economic benefits of implementing SBAS SA CAT I are mainly derived from the reduction in the number of aircraft diverted to other airports in low visibility conditions.

For CAT I airports:

  • CAT I airports may need incentives for developing low visibility procedures (LVP), especially small airports for which the economic benefits may not cover the required investment 
  • most of the benefits would go to airspace users, whereas most of the implementation costs would be paid for by the ANSP
  • this could concern up to 70 small airports and 30 medium airports in 25 different European countries 

For CAT II/III airports 

  • SA CAT I is used as a back-up of the ILS (with a DH higher than ILS CAT II)  
  • no additional infrastructure is required
  • this could concern up to 46 small airports, 46 medium airports and 30 large/very large airports in 29 different European countries


In CAT I airports, the economic benefits may not cover the required investment, especially in small and medium-sized airports, which are the typical size of CAT I airports. In this case, CAT I airports would probably prefer to invest in SA CAT I implementation (if the airport absolutely needs CAT II for their operations, they would probably have already invested in an ILS CAT II/III).

Disclaimer: The project results represent the views of the consortium. They do not necessarily represent the views of the European Commission and they do not commit the Commission to implementing the results.