The Aeronautical Information Exchange Model (AIXM)

The future Air Traffic Management (ATM) system will rely on advanced data exchange and data sharing services that communicate aeronautical information (infrastructure, route network, aerodrome, terrain, obstacle data) into the operational activities on the ground and in the air.

The Aeronautical Information Exchange Model (AIXM) is a specification that enables the encoding and the distribution in digital format of the aeronautical information. Although the term ‘aeronautical information’ might sound relatively generic, it clearly links AIXM to the ICAO Annex 15 – Aeronautical Information Services, which defines the information that ICAO contracting states have to provide internationally. This is also the primary scope of AIXM, which aims to support the transition from what is frequently referred to as ‘the current paper-based AIS system’ towards a more efficient and more capable Aeronautical Information Management (AIM) system, based on digital data exchange.

AIXM is also intended as a general purpose model for software applications that work with digital aeronautical data, at air navigation service providers, airports, airline operational centers etc. This has influenced the evolution of the model, which now encompasses data domains that go beyond the strict ICAO Annex 15 content, such as aerial refueling, procedure encoding, traffic flow restrictions, obstacle assessment surfaces etc. Furthermore, the model also provides a standard mechanism for extensions, which enables a community of interest to extend the core model with data of interest for that community.

Development and implementation

AIXM was originally developed by Eurocontrol to meet the needs of the European AIS Database (EAD). EAD is a central repository of quality assured data which enables the participating states to co-ordinate their aeronautical information updates, to produce and to distribute their AIP charts and NOTAM messages. Currently 40 European states are participating in the EAD operations, the objective being a full migration of all states that are members of the European Civil Aviation Conference (ECAC).

The initial AIXM versions (three and four) enabled the encoding in digital format of the static data contained in the national Aeronautical Information Publications (AIP). They also enabled the exchange of this data between the national databases and the centralised EAD reference database and further downstream to the EAD data users.

The latest AIXM version 5 is a joint development between Eurocontrol and the United States Federal Aviation Administration (FAA), supported by the international AIS/AIM community. Several objectives have driven this major update:

• Alignment with industry standards, in particular from the ISO 19100 series for geospatial information modeling and encoding
• Support for dynamic updates, which leads to the possibility to provide “digital NOTAM” and thus reform the oldest and most archaic component of the AIS system
• Going beyond the traditional AIP and NOTAM means for aeronautical information dissemination, by delivering an internationally agreed standard which enables the provision of real time aeronautical information in digital format

The result is a model with three key components:

• A conceptual/logical data model, which provides a formal description of the infor – mation managed by the Aeronautical Information Services (AIS). It is based on the ICAO Standards and Recommended Practices, on the content of the real world Aeronautical Information Publications (AIP) and on other relevant documents and industry standards, such as the ARINC 424 Specification
• A ‘temporality’ concept, which enables describing the variation in time of the properties of the aeronautical information features; this covers both baseline (static) data changes and temporary updates
• A data encoding specification, based on GML (Geography Markup Language), which is a specialised for of XML (Extensible Markup Language), a wide-spread data exchange standard

The latest AIXM version 5.1 is in the process of being adopted as ICAO Guidance Material, enabling the transition to digital aeronautical information services world-wide. An inter national AIXM Change Control Board (CCB) is planned to take over the responsibility for the maintenance and the evolution of the model, involving representatives of the major stakeholder groups: ICAO, ANSPs, industry etc. Eurocontrol and the FAA will continue providing the technical infrastructure and the administrative support for the model maintenance: modeling tools, change management tools, web site, forum, wiki, and secretariat.

Digital NOTAM

While most of the aeronautical data contained in AIP, charts and other publication of lasting character is available in digital format, the sudden and short lasting changes to the aeronautical environment are still published as text “NOtice To AirMen” (NOTAM). A NOTAM variant, called SNOWTAM, contains data about the airport surface contamination with water, snow or ice in winter conditions and about the friction. NOTAM and SNOWTAM are intended to be read by pilots, controllers and other operational personnel involved in flight operations.

As NOTAM and SNOWTAM contain information that is needed by automatic flight planning, pilot briefing, flight support and management systems, there is a stringent need for this information to be available in formats suitable for direct use by computers. This is partially achieved today through the manual encoding of certain NOTAM by commercial service providers and airline operational centres. However, this is an expensive, inefficient and error-prone process which covers only a small part of the almost 800,000 international NOTAM published every year world-wide. Full digital use of the NOTAM and SNOWTAM information requires that the data is originated and published directly in digital format, not reprocessed later in the data chain.

Therefore, the Digital NOTAM concept was developed jointly by Eurocontrol and the FAA, based on AIXM version 5, involving the international AIS community and in close cooperation with end users, in particular industry and airlines. A Digital NOTAM is a small data set, made available through more advanced communication networks (such as AMHS and TypeX). It is intended to be read and processed by automated systems, which in turn will convert it into text and graphical formats for presentation to humans. Digital NOTAM can be used, for example, in order to present an updated airport chart to the pilot or to the air traffic controller, containing graphical depictions of the work in progress areas, closed taxiways or runways and temporary obstacles. A Digital NOTAM might also trigger automated actions, such as determine procedures impacted by the unavailability of a navaid.

In Europe, the Digital NOTAM imple – mentation is planned to start by 2012, towards an initial operational capability. As result of business case analysis, an incremental implementation was selected as the most costeffective approach. Some event categories, such as airspace reservations, airport/runway closures, temporary obstacle etc. will be implemented in the first step. These have been selected based on their potential for digital use on short term and also considering that they represent 60 per cent to 80 per cent of the NOTAM issued in a European State.

Graphical SNOWTAM

In order to validate the Digital NOTAM concept and to demonstrate its advantages to the users, Digital NOTAM trials have been executed by Eurocontrol since 2008. The latest trial was focused on the encoding of SNOWTAM data in AIXM 5 format and the provision of graphical views of the contamination status of all airports for which SNOWTAM messages are usually published, in particular in Europe.

In the trial, the information contained in SNOWTAM messages is turned into AIXM 5.1 encoded data, which is in turn used to create graphical views:

• The ‘overview’ page presents the global status of the airports in the European Region using color-coded symbols for each airport
• The ‘Airport Zoom’ page shows the detailed status of each airport surface, for a given airport: type of contaminant, friction coefficient and latest measurement time

The trial application is limited to displaying the data that can be automatically decoded from the text SNOWTAM messages. This largely depends on the correctness and the completeness of these text messages, which cannot be guaranteed. The Digital NOTAM concept proposed that, in future, the data will be issued directly in AIXM format, thus avoiding the need to interpret and de-code loosely structured text.

Airport mapping data

Providing graphical representations of the status of the airport surfaces requires detailed and complete geometrical information for the runways, aprons and taxiways. This is also true for on-board applications, such as Electronic Flight Bags (EFB) devices that can be used to help the pilot preserving spatial awareness during taxiing. The growing need for such data led to the publication of a joint EUROCAE/RTCA specification: ED 99 / DO272 User Requirements for Aerodrome Mapping Information.

A part of the airport mapping data has been traditionally published as part of the Aeronautical Information Publications (AIP) of the states and reflected in the initial AIXM version. The latest AIXM 5.1 version also supports in detail the requirements for airport mapping data expressed by industry, in order to support the publication by the airports and/or by the AIS offices of such data.

About the Author

Eduard POROSNICU studied at the University Politehnica in Bucharest, from which he holds a graduation diploma in Aircraft Engineering. After a short training in procedure design and aeronautical information, he started working for the Civil Aviation Authority of Romania, AIS and Navigation Department.