The Airport Local Air Quality Studies (ALAQS) and Open-ALAQS


ALAQS (Airport Local Air Quality Studies) is an application that simplifies the process of defining the various airport elements (runways, taxiways, buildings, etc.) and allows the spatial distribution of emissions to be visualised.

ALAQS provides a four-dimensional emission inventory for an airport in which the emissions from the various fixed and mobile sources are aggregated and subsequently displayed for analysis. Once the emission inventory has been established, dispersion modelling (not yet included in ALAQS) can be used to calculate pollutant concentrations at the airport and in the surrounding area over a given period. The system is thus compatible with legislative requirements for 8-hour, 24-hour, and annual mean values of pollutant concentrations.


ALAQS was developed by the EUROCONTROL Experimental Centre between 2002 and 2009 under the name ALAQS-AV (ESRI ArcView ® GIS version). Version 2.0 of ALAQS-AV (Dec. 2009) has been approved for use by the ICAO Committee on Aviation Environmental Protection (CAEP) (see CAEP/9-IP/13).

However, ALAQS-AV is no longer supported by EUROCONTROL due to new technological orientations.



A new version of the ALAQS application called Open-ALAQS is under development.

This new version is based on an open-source GIS (QGIS) and an open-source database (SQLite), and is completely built around an open architecture which will make it easily adaptable to other GISes and databases.

Open source


Previously known as "Quantum GIS".

This is a cross-platform, free and open-source desktop geographic information system (GIS) application that provides data viewing, editing and analysis capabilities.
SQLite This is an open-source relational database management system.

Open-ALAQS retains the philosophy of the original application: bringing together state-of-the-art methods and databases to provide users with a test-bed for research (e.g. comparing various dispersion models based on the same emission inventory) and for the evaluation of operational improvements at airports. A significant amount of effort has been put into the design of a modular approach for Open-ALAQS, which has resulted in a clear separation of critical elements (user interface - methods - data format) as well as dedicated modules for each type of emission source. This will facilitate further improvements and maintenance of the toolset.

This new version is also being used to carry out a new CAEP local air quality model evaluation exercise.

The Open-ALAQS license agreement will be available in the near future.


Typical applications

The Open-ALAQS toolset provides the classic Local Air Quality features, enhanced to allow comparison of different methods. It is designed for the following application areas:

  1. 4D Airport emission inventories using a selection of inventory methods on all sources related to airport activity on an hourly basis, including aircraft, road vehicles (landside and airside), ground handling (GSE, APU, GPU), infrastructure, power plants, etc.)
  2. Air Pollution Dispersion Assessment: Estimate the dispersion of emissions, and model local air pollution concentrations for actual, generic and future situations.
  3. Mitigation Planning: Forecast the efficiency in air pollution abatement of measures proposed for reducing emissions from airport-related sources, together with issues concerning the sustainable growth of an airport.
  4. Monitoring: Compare modelled and measured pollutant concentrations at specific points to support airports in the implementation of EU directives (e.g. Council Directive 1999/30/EC) on air quality and monitoring.

Airport emission-source modelling

Open-ALAQS takes the following stationary and mobile emission sources into account:

  • Aircraft-related: gates, runways, taxiways and tracks
  • Stationary and mobile non aircraft-related: area sources - car parks, roadways; point sources - incinerators, heaters, fuel tanks, fire-fighting exercises, generators, etc.

It calculates the following emissions:

  • Carbon dioxide (CO2)
  • Carbone monoxide (CO)
  • Hydrocarbons (HC)
  • Nitrogen oxides (NOX)
  • Sulphur oxides (SOX)
  • Volatile organic compounds (VOC)
  • Particulate matter (PM)

Aircraft emissions are movement driven and may be calculated from a single aircraft movement (arrival or departure) up to a whole year’s worth of movements. An Open-ALAQS study is based on a detailed aircraft movement or operation journal which can be built from any archived data source of 4D air traffic  trajectories, such as simulator output, real radar data or basic flight plan data. Future scenarios can be derived from simulator data or projected traffic data. Fleet changes can be modelled allowing for technology changes if the user provides the necessary aircraft performance, emission and fuel burn data. Trajectories can either represent individual flights in the form of flightID, time, Latitude-Longitude-FL (X,Y,Z), or a generic flight such as an SAE1845 profile with a default ground track.

Aircraft emission inventories in the vicinity of airports are often calculated using ICAO engine exhaust emission data and the ICAO certification reference LTO cycle below 3000ft as illustrated in the diagram. Whilst Open-ALAQS will allow emissions to be calculated using the certification LTO cycle, the features built into Open-ALAQS allow a much higher resolution and accuracy to be used. The operational aircraft LTO cycle can be defined in more detail depending on the study requirements. Each movement (arrival, departure) can be assigned its exact engine, taxi route, climb/descent profile and airborne ground track. 

For any of these parameters, the corresponding data must also be provided. For example, if the engine fit is specified, the engine fuel flow and emission indices for the different LTO phases of flight must be provided. For those parameters that are not explicitly specified, Open-ALAQS will use pre-defined default values based on most likely values for a European airport.

Thus for a fully specified movement journal the emissions inventory will be based on the 4D trajectory of each movement between the stand and the top of the study (e.g. 3000ft AAL). The performance characteristics and/or fuel flow for each flight mode, and the corresponding emission indices, must be defined.

Gate emissions during aircraft turn-around from the handling equipment GSE/GPU and the aircraft’s Auxiliary Power Unit (APU) can be defined in as much detail as required for a study; from individual movements up to generic values for aircraft groups. Non-aircraft emission sources can be modulated using activity profiles. (See thumbnail)

Once the study data have been collected and characteristics have been set up in the GIS tool, one or more emission inventories can be run. The results from an emission inventory are in the form of 3D grids - one grid per hour simulated. Dispersion modelling can be performed over the available inventory runs using dispersion models.


Emission factors database used for the emission calculation
Aircraft emission factors Open-ALAQS makes use of the ICAO Engine Emissions Databank (issue 20, March 2014) for aircraft jet engine emission factors and the FOCA piston engine emission factors (issued 1/5/09). Open-ALAQS allows authorised users to use turboprop emission factors from the confidential FOI data base. A specific module has been developed with Open-ALAQS to automate the update of emission factors when a new version of the ICAO, FOCA or FOI database is issued.
Road traffic emission factors

The Open-ALAQS method for roadway emissions has been adapted from the COPERT IV method and emission factors. Fleet statistics for European countries have been obtained from the COST 319 project. These are used in combination with the average speed on every road segment to calculate segment-specific emission factors for CO, NOX, VOC and PM10.

 It should be noted that Open-ALAQS does not yet include a dispersion model, but allows data export to such models.

Open-ALAQS Team

Centre du Bois des Bordes
CS 41005
91222 Brétigny-Sur-Orge Cedex