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Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Abbreviation	Description
a	atto (SI unit multiplier of 10^18).
a	semi-major axis of ellipse (for WGS-84 = 6,378,137 m).
A/A	air-to-air.
A/D	(a/d) aerodrome.
A/D	analogue-to-digital.
A/G	air-to-ground.
A/J	anti-jamming.
A1A	CW telegraphy (eg morse code) keying the transmitted signal.
A2A	CW telegraphy (eg morse code) keying the modulation only.
AA	Aircraft Address (unique ident 24 bit ident number - ICAO Mode S).
AAA	airfield avoidance area.
AAAF	Association Aeronautique et Astronautique de France.
AAC	aeronautical/airline administrative communications.
AAC	Army Air Corps.
AAD	Additional Airworthiness Directive.
AAD	assigned altitude deviation.
aae	above aerodrome elevation.
AAF	Army Air Field (US).
AAI	Airports Authority of India.
AAI	angle of approach/attack indicator.
AAIB	Air Accidents Investigation Branch (of UK DfT).
AAIM	aircraft autonomous integrity monitoring.
aal	above aerodrome level.
AALA	Adventure Activities Licensing Authority (UK).
AAPS	Automated Aid Positioning System (US).
AATCU	ATCOs' union in Serbia & Montenegro.
AB	Able Seaman.
ab initio	'from the beginning' (elementary training).
A-band	NATO radar band 0-250 MHz = > 1.2 m.
ABAS	aircraft-based augmentation system.
ABIP	Advisory Board of Interested Parties (EASA).
ABLOS	Advisory Board on the Law of the Sea (IHO, IAG & IOC).
abm	abeam (at 90 degrees to track).
ABn	aerodrome beacon.
ABOI	Association of British Offshore Industries.
ABP	active bus priority (traffic lights).
ABP	Association of British Ports. London based private company owning several UK ports.
ABS	Acoustic Backscatter System.
ABS	American Bureau of Shipping (classification society). HQ Houston, TX, USA. European HQ London.
ABS	Automatic Blink System (LORAN-C integrity channel).
absolute accuracy	(geodetic or geographic accuracy). The accuracy of a position with respect to the geographic or geodetic coordinates of the earth (IMO).
AC	Admiralty Chart.
AC	Advisory Circular (FAA).
ac	aircraft.
AC	altocumulus cloud.
AC	Analysis Centre (IGS).
AC(YPS) Act	Activity Centres (Young Persons' Safety) Act 1995 (UK).
Acacia	Project to develop a definitive, consistent and joined-up national infrastructure of property addresses and related data with the related mapping. OS, HMLR, RoS, Valuation Office Agency (VOA), Improvement and Development Agency (IDeA) and Royal Mail.
ACARE	Advisory Council for Aeronautics Research in Europe.
ACARS	Aircraft Communications Addressing and Reporting System (ARINC). Civil air data link for air-to-ground business and ATS messages.
ACAS	Airborne Collision Avoidance System (=TCAS in USA). ACAS-II current from 2000. Mandatory in Europe for ac >5,700 kg MTOW or >19 pax seats from 1 Jan 05.
Acc	altocumulus castellanus cloud.
ACCa	adaptive cruise control.
ACCa	Antarctic Circumpolar Current.
ACCb	area control centre (ATC - international; ARTCC in US).
ACCLAIM	Antarctic Circumpolar Current Levels by Altimetry and Island. Contributes to the World Ocean Circulation Experiment (WOCE) of the World Climate Research Programme.
accuracy	The degree of conformance between the estimated or measured parameter of a craft at a given time and its true parameter at that time (IMO).
ACDS	Aeronautical Charts and Data Section (CAA).
ACE	Advanced Configurable EGI.
ACE	ATM Cost-Effectiveness (EUROCONTROL Benchmarking Report).
ACEA	Association des Constructeurs Europeens d'Automobiles. Represents the interests of 13 European car, truck and bus manufacturers.
ACEM	Agence de Cooperation pour Europe de la Mer (= ECMA).
ACF	autocorrelation function.
ACFD	advanced civil flight deck.
ACG	ATM/CNS Consultancy Group (EATCHIP - EUROCONTROL).
ACI	Airports Council International. 573 members with 1,640 airports in 178 countries (2008).
ACK	acknowledge(ment).
ACN	Active Control Network (UK OS).
ACN	Airspace Co-ordination Notice.
ACO	Aircraft Certification Office.
ACP	Airspace Change Proposal (UK CAA).
ACR	aerodrome control radar.
ACRUDA	Assessment and Certification Rules for Digital Architectures (EU).
ACTD	advanced concept technology demo.
ActMAP	EC project to bring real-time info to in-vehicle digital maps.
ACZ	aerodrome control zone.
AD	air data.
AD	Airworthiness Directive. Issued by airworthiness authority to correct a defect found after certification. Mandatory.
ADA	advisory area (ATC).
ADACU	advanced digital antenna control unit (eg for GPS steerable array).
ADAM	Airport Datum Management Program (US).
ADAS	Advanced Driver Assistance System.
ADC	aerodrome control(ler).
ADC	air data computer.
ADC	analogue-to-digital converter.
ADCC	Air Defence Control Centre.
ADCP	Acoustic Doppler Current Profiler.
ADD	aircraft-derived data.
ADD	airstream direction detector.
ADD	average delay per delayed flight (air traffic flow management).
Address Point	Dataset to uniquely define & locate residential, business and public postal addresses in GB. Matches info fm OS digital map databases with >26 million addresses in the Royal Mail PAF.
ADEOS	ADvanced Earth Observation Satellite (Japan).
ADEXP	ATS Data Exchange Protocol (EATMP).
ADF	automatic direction find(er)(ing).
ADI	attitude director indicator.
ADM	average delay per movement (air traffic flow management).
ADMAP	Antarctic Digital Magnetic Anomaly Project.
ADNM	Admiralty Digital Notice to Mariners.
ADONIS	EU project to make cycling and walking safer.
ADPCM	adaptive differential pulse code modulation.
ADR	accident data recorder.
ADR	advisory route (ATC).
ADRIS	automatic DR indicating system.
ADRU	Air Defence Radar Unit.
ADS	Automatic Dependent Surveillance.
ADS-B	Automatic Dependent Surveillance - Broadcast. Aircraft broadcast their identity, position (GNSS-based)and velocity. This can be captured by receivers on the ground (ADS-B out) or in aircraft (ADS-B in).
ADS-C	Automatic Dependent Surveillance - Contract.
ADSL	Asymmetric Digital Subscriber Line. For access to the Web using normal phone lines at speeds between 512 and 2,000 kbps.
ADSP	Automatic Dependent Surveillance Panel (of ICAO).
ADVANCE	Advanced Driver & Vehicle Advisory Navigation Concept (US).
ADVANTIS	Project looking at integrity for liability-critical applications (GJU).
AE	antenna electronics.
ae	Earth's equatorial radius (typically 6.378 x 106 m).
AEA	Association of European Airlines.
AEEC	Airlines Electronic Engineering Committee (US).
AEI	air experience instructor.
AENA	Aeropuertos Espanoles y Navegacion Area (Spanish ATSP).
AEP	Architecture Evolution Plan. GPS ground control Unix-based system from Apr 07.
AEROSAT	Aeronautical Satellite (Programme).
AESIG	Asociacion Espanola de Sistems de Informacion Geografica y Territo.
AEW	airborne early warning.
AF	adaptive filtering.
AFB	Air Force Base (US).
AFC	automatic frequency control (eg in radar).
AFCI	arc fault circuit interruption (to detect aircraft wiring problems).
AFCS	automatic flight control system.
AFDC	autopilot flight director computer.
aFDPS	Advanced Flight Data Processing System (precursor to SESAR).
AFDS	autopilot flight director system.
AFDX E/S	aircraft full-duplex end system.
AFG	Advisory Financial Group (EUROCONTROL).
AFI	assistant flying instructor.
AFI	automatic fault indication.
AFIGEO	Association Francais pour Information Geographique.
AFIS	airfield flight information service (info but not control).
AFLT	Advanced Forward Look Trilateration. To calculate position of a mobile handset on CDMA network.
AfOL	Association for Outdoor Learning (UK).
AFRAA	African Airlines Association.
AFRIN	Associate Fellow of the Royal Institute of Navigation.
AFS	Air Force Station (US).
AFS	atomic frequency standard.
AFSPC	Air Force Space Command (USAF).
AFSS	automated flight service station.
AFTN	Aeronautical Fixed Telecommunication Network.
AGAS	Action Group for ATM Safety (EUROCONTROL). Set up as high-level group as result of 1 Jul 02 mid-air collision.
AGC	Air/Ground Cooperative (Air Traffic Services Programme).
AGC	automatic gain control.
AGI	air ground incident.
AGI	Association for Geographic Information (UK).
AGILE	Application of Galileo in the LBS environment (EC FP6 2005-07).
agl	above ground level.
AGNA	Advisory Group of National Authorities (EASA).
AGNIS	Azimuth Guidance for Nose-in Stand (aircraft parking system).
AGNSS	(A-GNSS) Assisted GNSS.
A-GNSS	(AGNSS) Assisted GNSS.
AGO	automatic geophysical observatory.
AGORA	Implementation of Global Location Referencing Approach. EC telematics project Oct 2000 - Apr 2002.
AGPS	(A-GPS) Assisted GPS.
A-GPS	(AGPS) Assisted GPS.
AGS	Association of Geotechnical and Geo-environmental Specialists.
AGU	American Geophysical Union.
AHARS	attitude and heading reference system.
AHEAD	EUROCONTROL programme to develop web-based AIS.
AHMS	Aeronautical Mesage Handling System (to replace AFTN in 2000+).
AHRS	attitude and heading reference system.
AHS	Advanced Cruise-Assist Highway Systems (Japanese concept).
AHS	automated highway system.
AHWG	ad-hoc working group.
AI	Accuracy and Integrity (Galileo Service).
AI	attitude indicator.
AIAA	American Institute of Aeronautics and Astronautics.
AIAA	area of intense aerial activity.
AIB	Accident Investigation Board.
AIC	Aeronautical Information Circular.
AIC	Automotive Information Centre (MIRA).
AIDU	Aeronauical Information Documents Unit (RAF Northolt).
AIG	Association international de geodesie (IAG).
AIM	Aeronautical Information Management.
AIM	autonomous integrity monitoring (eg CAIM, RAIM).
AIN	Arab Institute of Navigation.
AION	Australian Institute of Navigation.
AIP	Administrative Incentive Pricing. Spectrum pricing to reflect its value to the user.
AIP	Aeronautical Information Publication.
AIPA	Australian & International Pilots Association.
AIPCN	Association Internationale de Navigation (also PIANC). Brussels based - www.pianc-aipcn.org.
AIRPROX	UK term for 'airmiss'.
AIRS	Automatic Ship Identification and Reporting System (UK).
AIRWAVES	Project to use GNSS in aircraft to monitor WV (EUROCONTROL).
AIS	Aeronautical Information Service.
AIS	Automatic Identification System (for shipping - IMO). For ship-to-ship and ship-to-shore exchange of dynamic (inc pos, SOG, COG, hdg, ROT), static (inc MMSI, callsign, name, size, type) and voyage (inc draft, cargo, dest, ETA, route plan) data. Uses 2 VH
AISM	Association Internationale de Signalisation Maritime (IALA).
AIV	all in view (receiver).
AIWG	Airspace Infringements Working Group (CAA).
AIZ	aerodrome information zone.
AL	alert limit/level. Max allowable error (in a measured position for example) found during integrity monitoring before an alarm is triggered.
ALA	approach and landing accident.
ALAR	Approach and Landing Accident Reduction (FSF initiative).
ALARP	as low as reasonably practicable (of risk in using a system).
Alert	The International Maritime Human Element Bulletin (NI & LloydÕs R).
ALFENS	Automated Low Flying Enquiry & Notification System.
ALI	automatic location identification.
aliasing	Visibly jagged steps along angled lines/edges (displays & maps).
ALIVE	ALert Interface Via EGNOS. System to broadcast warning messages (e.g. of natural disasters) in addition to the EGNOS correction signals.
ALL	Admiralty List of Lights.
ALNOT	Alert Notice (of aircraft overdue).
along-track error	A position error in the direction of the intended track (IMO).
ALPA	Air Line Pilots Association (US).
ALPR	automatic licence-plate recognition.
ALRS	Admiralty List of Radio Signals.
ALS	aerodrome lighting system.
AltBOC	Constant envelop modulation scheme for combining 2 sidebands each consisting itself of 2 binary signals (in I- and Q-channel).
AltBOC(n,m)	AltBOC with chipping rate of m x 1.023 Mcps and sub-carrier frequency of n x 1.023 MHz.
AM	amplitude modulation.
AM	ante meridian (before noon).
AM/FM Europe	Automated Mapping/Facilities Management - European Division.
AM/FM It	Automated Mapping/Facilities Management - Italy.
AMASS	Airport Movement Area Safety System (FAA) (software package).
ambiguity	The condition obtained when one set of measurements derived from a navigation system defines more than one point, direction, LOP or surface of position (IMO).
AMCP	Aeronautical Mobile Communication Panel (of ICAO).
AMCS	Alternate Master Control Station (GPS) - Vandenberg AFB.
AME	authorised medical examiner (for aviation licences).
AMI-C	Automotive Multimedia Interface Collaboration (telematics standard).
AMLCD	active matrix liquid crystal display.
amphidrome	A point in the sea where there is zero tidal amplitude due to cancelling of tidal waves. Cotidal lines radiate from an amphidromic point and corange lines encircle it.
AMSA	Australian Maritime Safety Agency.
AMSD	Aircraft Maintenance Standards Department (CAA SRG).
amsl	above mean sea level.
AMSS	Aeronautical Mobile Satellite Service.
AMTICS	Advanced Mobile Traffic Info & Communication System (Japan).
AMVER	Automated Mutual-Assistance VEssel Rescue System (USCG).
ANA	area navigation approach.
ANASTASIA	Airborne New and Advanced Satellite techniques and Technologies in A System Integrated Approach (EC FP6 project)
ANAVnet	On-line application to distribute marine warnings (IHPT).
ANC	Air Navigation Commission (ICAO).
Android	mobile phone operating system for web (Google) 2008.
ANMS	Automated Notice to Mariners System.
ANO	Air Navigation Order. Statutory legal instrument defining the laws of air navigation, pilot licensing etc in UK.
ANP	actual navigation performance.
ANPA	Advanced Notice of Proposed Amendment (JAR-OPS).
A-NPA	Advance Notice of Proposed Amendment (EU JAA).
ANPAC	Associazione Nazionale Piloti Aviazione Commerciale (It pilots Assoc).
ANPCAT	ATCOs' union in Italy.
ANPR	automatic number plate recognition.
A-NPRM	Advance Notice of Proposed Rulemaking (FAA, FCC etc).
ANR	active noise reduction.
ANSEP	Air Navigation Services Economics Panel (ICAO).
ANSI	American National Standards Institute.
ANSP	air navigation service provider.
ANT	Airspace and Navigation Team (EUROCONTROL).
ANT	antenna.
AOA	Airport Operators Association.
AOA	angle of arrival.
AOB	angle of bank.
AOC	Advanced Operational Capability.
AOC	aerodrome/airport obstruction chart.
AOC	aeronautical operational control (US military).
AOC	Air Operator's Certificate.
AOC	aircraft operations centre.
AOC	airline operational control.
AOC	airline operations communications.
AOC	auxiliary output chip.
AOM	aircraft operating manual.
AOO	area of operations.
AOPA	Aircraft Owners and Pilots Association.
AOR	Atlantic Ocean Region (-E or -W) (of Inmarsat III satellites). AOR-E at 15.5 degrees W, AOR-W at 54 degrees W but moving to 98 degrees W in early 05.
AP	access point.
AP	air position.
AP	Air Publication (RAF) (AP3456 covers navigation).
AP	assumed position (estimated position for astronomical sight reduction).
AP	autopilot.
APAC	Asia and Pacific (ICAO area).
APAPI	abbreviated precision approach path indicator.
APC	airline passenger correspondence (eg e-mail, internet, phone).
APC	approach control(ler) (ATC).
API	air position indicator.
API	application programming interface.
APL	Advanced Positioning Layer (LBS).
APL	airport pseudolite.
APOLO	Advanced POsition LOcator (train location system using GNSS).
APP	approach (control).
APR	approach control radar.
APRS	automatic position reporting system.
APTS	Advanced Public Transport System.
APU	auxiliary power unit.
APV-I	Approach with Vertical Guidance - 1 (to runway). Requires accuracies (95%) of 220 m H, 20 m V. HAL 556 m, VAL50 m. Time to alert 10 s. Definition may be changed by FAA in 2002-03.
APV-II	Approach with Vertical Guidance - 2 (to runway). Requires accuracies (95%) of 16 m H, 8 m V. HAL 40 m, VAL 20 m. Time to alert 6 s.
AR	augmented reality (VR images overlaid on the real world).
AR	autoregressive (form of Kalman filter).
ARA	airspace restricted area.
ARB	Airworthiness Requirements Board (CAA).
ARC	Atlantic Rally for Cruisers.
ARCC	Aeronautical Rescue Co-ordination Centre.
ARCC	Associated Rescue Co-ordination Centre. Centre nominated by national SAR agency to which CES normally routes distress calls.
ARCS	Admiralty Raster Chart Service.
ARCS	automatic route control system.
ARINC	Aeronautical Radio Inc (now just called 'ARINC'). US avionics standards-setting body whose standards are accepted world-wide.
ARKTRANS	Norwegian ITS architecture.
ARM	Series of processor cores from ARM Ltd.
ARMAS	Active Road Management Assisted by Satellite (ESA project).
ARN	ATS Route Network.
ARNS	Aeronautical RadioNavigation Service (of allocated spectrum bands).
ARP	aerodrome reference point.
ARPA	automatic radar plotting aid.
ARPU	annual/average revenue per user/unit (of eg a telematics service).
ARSR	air route surveillance radar.
ARTCC	air route traffic control centre (US; ACC internationally).
ARTEMIS	Advanced Relay and TEchnology MIssion Satellite (ESA). Planned to carry EGNOS navigation payload from mid-2001; actually achieved orbit in Jan 2003. 21.5 degrees E.
ARTES	Advanced Research in TElecommunications Systems. ESA initiatives. Element 9 involves development work for GNSS.
ARTIST	Austrian Radionav Tech & Integrated Sat Nav Servs & Products T'bed.
ARTIST	Italian ITS architecture.
ARU	aircraft retained unit (piece of aircrew equip that stays with the ac).
ARW	angular random walk (of a gyro).
As	altostratus cloud.
AS	anti-spoofing. Method of protecting against hostile imitation of signals - eg GPS PPS
AS	aviation safety.
A-S	anti-spoofing. In GPS the use of encryption to prevent a P-Code receiver locking to a bogus P-Code transmission.
ASAB	Association of Animal Behaviour.
ASAP	Aviation Safety Action Programme.
ASAS	Airborne Separation Assurance System.
ASCII	American Standard Code for Information Interchange. Comprises letters, digits and special characters each represented by 8 bits or 1 byte.
ASDE	airport surface detection equipment (radar) (can feed AMASS).
ASDO	automatic selective door operation (rail).
ASE	altimetry system error.
ASECAP	Association Europenne de Concessionnaires d'Autoroutes et douvrages Page
ASF	additional secondary factor (cause of Loran sig delay - also PF & SF).
ASF	Air Safety Foundation (of the US AOPA).
ASI	Agenzia Spatziale Italiana (Italian National Space Agency).
ASI	Airspace and Safety Initiative (UK CAA).
ASI	airspeed indicator.
ASIC	application-specific integrated circuit. An IC designed or adapted for a specific application.
ASK	available seat kilometres (a measure of civil available air capacity).
asl	above sea level.
ASL	application simulation level.
ASM	airspace management.
ASMGCS	Advanced Surface Movement Guidance and Control System (airfield).
A-SMGCS	Advanced Surface Movement Guidance & Control System.
ASMI	airfield surface movement indicator.
ASMS	advanced satellite mobile system (future comms).
ASOS	Automated Surface Observation System (US - air).
ASP	application service provider.
ASP	average selling price.
ASQF	Application Specific Qualification Facility (EGNOS - Torrejon).
ASR	airport/airfield surveillance radar.
ASR	altimeter setting region.
ASR	aviation safety report.
ASRS	Aviation Safety Reporting System (NASA).
ASR-WSP	airport surveillance radar - weather systems processor (FAA).
Assignment	Authorisation given by a licensing authority for a radio station to use a specific radio frequency or channel under specified conditions.
ASSIST	Alpine Safety, Security & Informational Services & Technologies.
ASSP	Application Specific Standard Product. IC dedicated to one specific application (like a custom IC) but with several possible customers (unlike a custom IC).
ASTE	Advanced System Telecommunication Equipment programme (ESA).
ASTRA	Application of Space Techniques Related to Aviation.
ASTRAEA	Autonomous Sys Technology Related Airborne Eval & Assessment. Project to develop the next-generation of UAVs for civil applications.
ASTRON	Applications on the Synergy of Earth Obs with Sat Telecoms & Nav. Under EC 5th Framework RTD Programme.
Astronomical lat	Angular distance between the plane of the celestial equator and the point's plumb line.
Astronomical lon	Angle between the plane of the prime meridian and the plane of the point's celestial meridian.
ASV	Advanced Safety Vehicle (Japanese concept).
AT	atomic time.
ATA	actual time of arrival.
ATA	Air Transport Alliance (EU).
ATA	Air Transport Association (US).
ATA	automatic tracking aid.
ATAG	Air Transport Action Group. Industry lobby gp, 80 members funded by IATA, Boeing and Airbus.
ATC	adaptive tightly-coupled (eg GPS/INS integration).
ATC	air traffic control.
ATC	automatic train control.
ATC EUC	Air Traffic Control European Union Co-ordination (~8,000 ATCOs).
ATCAA	air traffic control assigned airspace.
ATCC	air traffic control centre.
ATCO	air traffic control officer.
ATCRBS	Air Traffic Control and Radar Beacon System.
ATCRU	air traffic control radar unit.
ATD	actual time of departure.
ATE	along track error.
ATE	automatic test equipment.
ATF	adaptive transversal filter (eg for minimising jamming signals).
ATFM	air traffic flow management.
ATIS	advanced traveller information system.
ATIS	Alliance for Telecommunications Industry Solutions (US).
ATIS	automatic terminal information station/service. Continuous broadcast of routine non-control aerodrome information.
ATK	available tonne kilometres. Measures air available total capacity (combined passenger and cargo).
ATLAS	Airborne Topographic Laser System (QinetiQ).
ATLB	Air Transport Licensing Board.
ATM	aerodrome traffic monitor.
ATM	air traffic management. ATM2000 is EUROCONTROL's gate-to-gate strategy initiative to 2015.
Atmosphere	Shell round earth extending to height of 350 km. Comprises troposphere, stratosphere, mesosphere, thermosphere and ionosphere.
ATMS	advanced traffic management system.
ATMSP	Air Traffic Management Service Provider. eg: AENA - Spain, ANA - Portugal, DFS - Germany, DGAC - France, ENAV - Italy, NATS - UK.
ATMWG	Air Traffic Management Working Group (IATA).
ATN	Aeronautical Telecommunications Network.
ATOL	Association of Tour Operators and Leaders.
AtoN	(ATON) aid(s) to navigation.
ATOP	Advanced Technologies and Oceanic Procedures (FAA).
ATP	Allied Tactical Publication (NATO).
ATP	Automatic Train Protection (UK signalling safeguard).
ATPI	Along the Track Protection Interval (trains).
ATPL	Air Transport Pilot's Licence.
ATR	Air Transport Racking (ARINC). A standard size for avionics boxes. All 10 ins high, full ATR 10 ins wide, half ATR 5 ins wide etc.
ATS	air traffic service.
ATS	Aircrew Training System (USAF).
ATSA	air traffic service assistant.
ATSB	Australian Transport Safety Board.
ATSI	air traffic services investigations.
ATSIN	Air Traffic Services Information Notice (CAA).
ATSOCAS	air traffic services outside controlled airspace.
ATSP	Air Traffic Service Provider.
ATSU	air traffic service unit.
ATT	Admiralty Tide Tables.
ATT	advanced transport telematics.
ATTS	advanced transport telematics system.
AT-VASIS	Abbreviated 'T' Visual Approach Slope Indicator System.
ATZ	aerodrome traffic zone. Usually 2 or 2.5 n miles radius up to 2,000ft aal.
AU	astronomical unit.
AUC	Air Transport Users' Council (UK CAA - 12-20 members).
augmentation	Any technique of providing enhancement in order to provide improved navigation performance to the user (IMO).
AUGUR	A predictive GPS receiver autonomous integrity monitoring system. EUROCONTROL.
AUM	all-up mass (aircraft).
AUTM	Authorised Unusable Time (NELS Loran-C - see also UTM and EUTM). Scheduled and authorised UTM with at least 72 hrs of notice.
AutoBAHN	Pinpoint project towards millimetre accurate real-time positioning. Newcastle University & LogicaCMG.
AUTS	additional user terminal sensor (GNSS).
AUV	autonomous underwater vehicle.
AUW	all-up weight (aircraft).
availability	The percentage of time that an aid, or system of aids, is performing a required function under stated conditions (IMO).Signal availability - of a radio signal in a specified coverage area.System availability - of a system to a user.
AVC	automatic vehicle classification.
AVCS	advanced vehicle control system.
AVG	automatic vehicle guidance.
avgas	aviation gasoline (for piston aircraft).
AVI	automatic vehicle identification.
AVIC	audio, video, information and communication (eg for aircraft pax).
AVID	Added Value Information Dissemination (EU project).
AVL	automatic vehicle location.
AVLS	automatic vehicle location system.
AVM	automatic vehicle monitoring.
AVOL	aerodrome visibility operational level.
AVT	Applied Vehicle Technology Panel (NATO RTO).
avtur	aviation turbine fuel (kerosine) (for jets/turboprops).
AWAC	airborne warning & control.
AWARE	Advanced Weather and Reporting Enhancements. Tool being developed by NASA to present better weather info for GA pilots.
AWDS	automated weather distribution system.
AWG	aural warning generator.
AWGAS	Aerial Work & General Aviation Sub-Ctee (JAA).
AWGN	additive white Gaussian noise.
AWN	Aviation Weather Network (US).
AWNIS	Allied Worldwide Navigational Information System. Classified NATO navigational warning system.
AWO	all-weather operations.
AWOP	All-Weather Operations Panel (ICAO).
AWOS	Automated Weather Observing System.
AWP	automated weather processor.
AWPR	automatic waypoint reporting.
AWR	airborne weather radar.
AWS	Automatic Warning System (UK railways).
Awy	airway.
az	azimuth.