EGNOS, the European Geostationary Navigation Overlay Service, is the European SBAS and has been deployed to provide regional satellite-based augmentation services to aviation, maritime and land-based users in Europe. EGNOS is the first step in the European Satellite Navigation strategy that leads to Galileo, the future European satellite navigation system that will complement GPS.
The European Satellite Services Provider (ESSP-SAS) is the central coordinator and the end-to-end responsible of the EGNOS operation and service provision. The ESSP-SAS is responsible for EGNOS Signal and Data Provision including operations management of the system infrastructure and operations teams for matters such as coordination and planning, first and second line maintenance activities, operations user interface and interface to industrial teams for third line maintenance activities.
- ESSP : EGNOS services provider
- European Commission : Programme Manager and system owner.
- European Space Agency : Delegated Design and Procurement Agent, intermediary between the Commission and industry for the development of new EGNOS system releases
- Thales Alenia Space : industrial prime contractor
- GSA : market development and management of FP7 funds to promote and accelerate EGNOS adoption
- Eurocontrol: supports the development and implementation of EGNOS approach procedures. Has developed a NOTAM tool and web-based interface for EGNOS availability forecasts, provides aviation user requirements and monitors the performance of the deployed system
- EASA : certifies EGNOS-enabled receivers and, in the future, the EGNOS services provider
EGNOS is a public utility and is intended to be free of direct user charges, like WAAS in the US. EGNOS will continue to exist even after Galileo has become operational. In fact, EGNOS will augment not only GPS but also Galileo.
There is a disclaimer stating that the Open Service is provided without service guarantees and associated liability. There is no certification of Open Service or its applications, it is offered for free to the user without any direct relationship with the provider and therefore the user retains the primary responsibility to assess when and how (i.e. alone or with other means of navigation) EGNOS should be used to best meet his needs. This disclaimer is necessary for legal reasons, to clarify the extent of the European Commission and/or the service provider liability in case of damages caused by reduced performance or signal interruption. It does not by any means reduce the European Commission's and the service provider's commitment to provide the highest possible accuracy and availability of the signal. For reference, many other widely used products and services also come without any guarantee and liability for similar reasons and that is also the case of GPS.
EGNOS is very similar to WAAS and fully interoperable with WAAS i.e. aircraft equipped with a WAAS-enabled receiver are able to use EGNOS. EGNOS is also interoperable with the Japanese MSAS.
Yes, EGNOS can be used for personal navigation in Europe, providing greater precision than when using the GPS signal alone. The receiver must be labelled as WAAS or EGNOS enabled. Additionally, in some enabled receivers the use of EGNOS corrections have to be manually activated
In order to centralize the user questions related to EGNOS and its applications, the ESSP operates a dedicated helpdesk service that among other topics, addresses questions such as:
- General questions on EGNOS services
- EGNOS coverage and performances
- Support to EDAS users
- Anomalies reporting
- EGNOS program
The EGNOS Helpdesk may be contacted at egnos-helpdesk@essp-sas.eu
Satellite Name: Inmarsat-3 AOR-E
PRN Number: PRN 120
Satellite Location (Longitude): 15.5° W
NMEA Number (Gamin receivers): 33
Satellite Name: ESA-Artemis
PRN Number: PRN 124
Satellite Location (Longitude): 21.5° E
NMEA Number (Gamin receivers): 37
Satellite Name: Inmarsat-3 IOR-W
PRN Number: PRN 126 (This PRN broadcasts the EGNOS TEST signal and is not used for operations)
Satellite Location (Longitude): 25.0°E
NMEA Number (Gamin receivers): 39
The services currently being provided by EGNOS are:
- EGNOS Safety of Life Service (SoL) This service is intended for applications where human life could be at a stake if the positioning system does not meet stringent integrity requirements.
- EGNOS Open Service (OS). Applications that have not the safety requirements met by the EGNOS SoL service, are considered to be Open Service applications.
- EGNOS Data Access Service (EDAS): this is the provision of EGNOS data through the internet.
It is important to point out that the service provided by EGNOS is dependent on the receiver at the user side
The main objective of the EGNOS Open Service is to improve the achievable positioning accuracy thanks to the correction of several error sources affecting the GPS signals.
This service is intended for applications that although requiring a high degree of accuracy, do not require the integrity features provided by EGNOS.
The Open Service is available from October 2009.
All the relevant information on the OS is provided in the Open Service Definition Document that can be found at http://www.essp-sas.eu/service_definition_documents
In addition to the enhanced accuracy provided by the OS, the EGNOS Safety of Life (SoL) service provides the stringent integrity, continuity and availability required to support Civil Aviation applications up to LPV (Localizer Performance with Vertical guidance) operations.
The EGNOS SoL service will also be usable in a wide range of other application domains (e.g. Maritime, Railways, Road…) but, at this stage, a detailed performance characterisation has only been conducted against the requirements expressed by civil aviation. The SoL Service is available since March 2011
In general, the EGNOS SoL Service is intended for most transport applications in different domains where lives could be endangered if the performance of the navigation system is degraded below specific accuracy limits without giving notice in the specified time to alert. This requires that the relevant authority of the particular transport domain determines specific requirements for the navigation service based on the needs of that domain, as well as certification procedures if necessary. In addition, the navigation operations based on the EGNOS SoL Service may require a specific authorisation, issued by the relevant authority, unless the authority, or applicable regulation, establishes that no such authorisation is required.
At present, only the aviation domain has specific service requirements, as well as certification and individual authorisation procedures developed and implemented
The EGNOS Data Access Service (EDAS) provided by the ESSP consists of the provision in almost real time of the same data that is broadcast by the EGNOS satellites (EGNOS Message) along with the GPS and Glonass measurements at all the stations of the EGNOS monitoring network (RIMS and NLES).
These data are obtained from the EDAS server through an specific interface software (EDAS Client Software) that is provided to the EDAS user upon registration.
Access is provided to EGNOS applications developers upon submitting the EDAS application form found at http://www.gsa.europa.eu/go/egnos/edas to the EGNOS Helpdesk and upon EC approval.
EGNOS performances are measured in terms of four parameters: Accuracy, Integrity, Continuity and Availability.
The definitions of these terms are:
- Accuracy: GNSS position error is the difference between the estimated position and the actual position. For an estimated position at a specific location, the probability should be at least 95 per cent that the position error is within the accuracy requirement. (ICAO SARPS).
- Integrity: is a measure of the trust which can be placed in the correctness of the information supplied by the total system. Integrity includes the ability of a system to provide timely and valid warnings to the user (alerts) when the system must not be used for the intended operation (or phase of flight). (ICAO SARPS).
- Continuity: is the capability of the system to perform its function without unscheduled interruptions during the intended operation. It relates to the capability of the navigation system to provide a navigation output with the specified accuracy and integrity during the approach, assuming that it was available at the start of the operation. (ICAO SARPS).
- Availability: is characterised by the portion of time the system is to be used for navigation during which reliable navigation information is presented to the crew, autopilot, or other system managing the flight of the aircraft. (ICAO SARPS).
The EGNOS Signal in Space is continuously being monitored by the ESSP and the performances obtainable using the real corrections broadcast by the system are provided at the EGNOS User Support website (http://egnos-user-support.essp-sas.eu/). Additionally, specific information on performances can be requested directly to the EGNOS Helpdesk (egnos-helpdesk@essp-sas.eu)
The service availability section of the EGNOS User Support website (http://egnos-user-support.essp-sas.eu/) provides information on EGNOS Signal interruptions. Information on EGNOS planned outages (due to operator maintenance activities) is available at http://egnos-user-support.essp-sas.eu/egnos_ops/EGNOS_system/SIS_status
When referring to EGNOS performances, it is usual to consider those attainable by an error free receiver using all the GPS satellites in view at location and with no multipath effects. This is necessary to provide a valid reference as the actual performances will depend in any case of the type of receiver, number of satellites used (usually less than all in view at location) and the local multipath effects.
- Nominal performances: Vertical accuracy is improved from 15 meters to 4 meters. Horizontal accuracy is improved from 10 meters to 3 meters.
- Observed performances:
Vertical accuracy is improved from 4-5 meters to around 2 meters.
Horizontal accuracy is improved from 2-3 meters to around 1 meter.
On top, EGNOS includes an integrity function i.e. a warning in case of an issue with the system, emitted within 6 seconds of the malfunction and repeated.
For the time being, EGNOS offers full coverage (APV-1 99%) over Austria, Belgium, Denmark, France, Germany, Luxemburg, Netherlands, Slovenia, Switzerland, Croatia, Bosnia and partial coverage over Czech Republic, Finland, Hungary, Ireland, Italy, Poland, Portugal, Slovakia, Spain, Sweden, United Kingdom, Norway, Montenegro and Serbia
For most of the applications of EGNOS, the receiver will select the EGNOS satellite from those available at that moment (typically the one providing better performance). In these cases, the change of GEO will be transparent to the end user. In the particular cases where the GEO used to compute the EGNOS corrections is manually selected, it should be set to an available one.
The EGNOS Signal in Space is being broadcast from two satellites for redundancy purposes only. This redundancy ensures that although during the normal operation of the system a low number of discontinuity events can be expected, the simultaneous outage of both satellites is extremely remote. This redundancy mitigates as well the masking effects of one of the GEOS by obstacles or other sources.
To receive the EGNOS signals, an EGNOS compatible receiver (also called SBAS receiver or WAAS receiver) is required. It is like a GPS receiver but with special software enabling the receiver to lock onto the EGNOS satellites and apply the EGNOS corrections to the GPS signal. Today, most of the commercial GPS receivers provide EGNOS capability
EGNOS Signal Format is described in the Appendix A of the Minimum Operational Performance Standards (MOPS) for Global Positioning System/Wide Area Augmentation System Airborne Equipment, RTCA/DO-229.
The RTCA DO229 WAAS MOPS documentation is available for sale at www.rtca.org
EGNOS Message Types (MT): The Message Type 0 (MT0) is used to indicate that the system is on test and cannot be used for safety critical applications they fall under the MOPS Do229A. Since April 2003, the Message Type 0/2 is implemented under the MOPS Do220C specs:. It consist of overlapping a message type 2, providing fast corrections, ionosphere corrections and ranging data, on the frame reserved to the message type 0. It still indicated that the system is on test mode, but it also optimizes the use of the SIS data capacity. There are a substantial number of receivers able to process EGNOS MT0/2 (Open Access Service), on the market.
- Certified SoL receivers (for example aviation ones), implement all the requirements set in the applicable standards (RTCA Do-229()) in order to achieve the integrity levels necessary for SoL applications. These receivers will stop using EGNOS whenever the SoL service is discontinued (by adding a Message Type 0 to the signal). This can occur if a system degradation could render the use of EGNOS unsafe for SoL applications. Additionally, and depending on the application field, SoL receivers may require a certification stamp from the relevant authority (in aviation, EASA or FAA for ETSO or TSO certified equipment respectively)
- Open Service receivers, on the contrary may have implemented only a subset of the requirements in DO-229, in particular, they may ignore the MT0 if broadcasted and keep providing corrections even when SoL is not available. Typically these receivers only apply the EGNOS corrections to improve accuracy but no indication of protection levels or integrity alerts are provided.
A list of SBAS receivers is available at : http://egnos-portal.gsa.europa.eu/developer-platform/developer-toolkit/r...
Yes, any WAAS capable receiver shall work with the other SBAS (Satellite Based Augmentation System). Today two SBAS are already being operated: EGNOS in Europe and WAAS in the USA. Two other SBAS systems are being developed GAGAN in India and MSAS in Japan. These are all civil-controlled regional systems and there is a form of coordination to ensure that they are interoperable to provide a seamless worldwide navigation system so that you can use one single SBAS receiver for all of them.
Each EGNOS SIS has three modes of operation:
- Test Mode: This mode is defined by the broadcasting of the MT0 (Message Type 0) in the signal. It indicates that the system is on test and is not usable. Receipt of a message type 0 will normally prompt the receiver to terminate the use of any message.
- Non-Safety-Of-Life Mode: This mode still indicates that the system is on test, but allows receivers to compute EGNOS corrections, improving the use of the SIS data capacity, as long as the signal is only used for non-safety-of-life applications. The mode consists of overlapping a message type 2 on the frame reserved for the message type 0.
- Safety-Of-Life Mode: EGNOS SIS may be used for Safety of Life applications. In this case, no message Type 0 is broadcast and message type 2 is broadcast normally.
The pseudoranges corrections of EGNOS Operated GEOs, PRN120 and PRN124 are not considered by the receiver when computing the navigation position solution (even though there are almanac and ephemeris data provided in messages type 9 and 17), as these two satellites are declared as NON USABLE for EGNOS through the UDRE indicators provided in messages type 4 and type 6
For passengers: increased safety thanks to allowing instrument approach procedures that are safer than non-precision approaches.
For airlines: allowing instrument approach procedures, which have much better performance than non-precision approaches. Resulting in fewer delays, diversions and cancellations due to bad weather/poor visibility at airports that are not equipped with ground-based navigation aids.
For airports not equipped with ground-based navigation aids:
- increased capacity as separation between aircraft can be reduced
- increased accessibility as planes can land even in bad weather/poor visibility conditions
- reduced costs compared to the installation and maintenance of ground-based navigation aids as EGNOS only requires an approach procedure for the runway
For airports equipped with ground-based navigation aids: cost-effective back-up for precision approaches.
In aviation, the EGNOS SoL Service is offered for all phases of flight within the corresponding EGNOS SoL Service area, to aviation users (further “Aviation Users”) namely:
• airspace users, as defined in the Single European Sky framework Regulation1, equipped with an EGNOS certified receiver and located within the appropriate EGNOS SoL Service area corresponding to the phase of flight in which the EGNOS SoL Service is used (as described in the EGNOS SoL SDD);
• certified Air Navigation Service Providers having signed a working agreement with ESSP SAS that is valid at the moment of the use of the EGNOS SoL Service.
EGNOS qualifies as a navigation service under the Single European Sky (SES) Regulations. As a consequence, the provision of the service by the EGNOS Service Provider (ESSP) is subject to certification and the system subject to an EU Declaration of Verification. This supervision was performed by the French national supervisory authority (DSAC). The European Aviation Safety Agency (EASA) will take over the continued compliance monitoring of EGNOS.
EGNOS is a key technical enabler to the SESAR operational concept. EGNOS will contribute to the achievement of the objectives of the Single European Sky policy. In particular, it will contribute to de-fragment the provision of navigation services thanks to its pan-European nature and will facilitate enhanced navigation performances, in line with the SES ATM Master Plan.
In Europe, ICAO recommends deploying approaches with vertical guidance at all runways by 2016 and EGNOS is one of the key technologies enabling the European regional PBN (Performance Based Navigation) plan, which aims at providing vertical guidance at all landing sites.
LPV stands for Localizer Performance with Vertical guidance. It is an Instrumental Approach Procedure that provides lateral and vertical guidance based on GPS augmented by SBAS (EGNOS/WAAS). The main advantage of this kind of procedures is to enable ILS like approaches (down to 250 ft minima) with a limited ground infrastructure (runway lighting). Therefore, EGNOS provides the benefit to extend the ability to perform instrumental approaches of almost ILS Cat I minima to runways where the installation of an ILS is not cost effective or technically feasible, as well as to provide an inexpensive backup to runway ends already equipped with an ILS. The benefits of this kind of procedures to the airlines is particularly significant to those operating from/to medium sized or light traffic aerodromes where an ILS is not available or cost effective due to both, the decreased number of flights cancelled or delayed and the commercial opportunities derived of an extended operational availability of the aerodromes.
Using EGNOS for instrument approaches can bring the decision height down to as low as 250 feet (about 75 meters), which is close to ILS Cat I. This means that the pilot can take the aircraft down "blind", without visual contact to the ground, to as low as 250 feet above ground. A subsequent version of EGNOS will allow for 200ft minima which is equivalent to ILS Cat I
You must:
1) design and publish an instrument approach procedure for your runway and have it approved by your National Supervisory Authority
2) your ANSP will be required to sign an agreement with the EGNOS Service Provider ESSP SaS, in particular to support exchange of technical and operational information
Your aircraft must be equipped with an SBAS-capable receiver, certified according to TSO or ETSO 145 or 146. Airworthiness certification and operational approval will be based on EASA AMC 20-28, which is expected to be published in 2012. In the meantime EASA is ready to provide approvals using the Certification Review Item (CRI) process and the draft AMC material.
In order to provide an overview of the EGNOS supported procedures implementation status and planning, the most recent data are published per country at Eurocontrol website: http://www.ecacnav.com/
The detailed information on the approved approach procedures is available at the corresponding National AIP