Automatic dependent surveillance-broadcast (ADS-B) is a cooperative surveillance technique for
air traffic controlAir traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
and related applications.
An ADS-B-equipped aircraft determines its own position using a
global navigation satellite systemGlobal Navigation Satellite Systems is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. GNSS allows small electronic receivers to determine their location to within a few metres using time signals transmitted along a...
and periodically broadcasts this position and other relevant information to potential ground stations and other aircraft with ADS-B-in equipment.
ADS-B can be used over several different data link technologies, including Mode-S Extended Squitter (1090 ES), Universal Access Transceiver (978 MHz UAT), and VHF data link (VDL Mode 4).
ADS-B provides accurate information and frequent updates to airspace users and controllers, and hence supports improved use of
airspaceAirspace means the portion of the atmosphere controlled by a particular country on top of its territory and territorial waters or, more generally, any specific three-dimensional portion of the atmosphere....
, reduced ceiling/visibility restrictions, improved surface
surveillanceSurveillance is the monitoring of the behavior, activities, or other changing information, usually of people and often in a surreptitious manner...
, and enhanced safety, for example through conflict management.
Under ADS-B, a vehicle
periodicallyPeriodicity is the quality of occurring at regular intervals or periods and can occur in different contexts:In timing devices:* A clock marks time at periodic intervals.* A metronome ticks at periodic intervals of time....
broadcastsright|250pxIn computer networking, broadcasting refers to transmitting a packet that will be received by every device on the network. In practice, the scope of the broadcast is limited to a broadcast domain...
its own
state vectorA geographical state vector is a set of data describing exactly where an object is located in space, and how it is moving. From a state vector, the object's current and future position can be determined....
and other information without knowing what other vehicles or entities might be receiving it, and without expectation of an acknowledgment or reply. ADS-B is
automatic in the sense that no
pilotAn aviator is a person who flies aircraft for pleasure or as a profession. The first recorded use of the term was in 1887 as a variation of the French 'aviation', from the latin 'avis', coined 1863 by G. de la Landelle in "Aviation ou Navigation Aérienne"...
or
controllerAir traffic controllers are the people who operate the air traffic control systems to expedite and maintain a safe and orderly flow of air traffic and help prevent mid-air collisions. They apply separation rules to keep aircraft apart from each other in their area of responsibility and move all...
action is required for the information to be issued. It is
dependent surveillance in the sense that the surveillance-type information so obtained depends on the suitable navigation and broadcast capability in the source vehicle.
A similar solution is the
Automatic Identification SystemThe Automatic Identification System is a short range coastal tracking system used on ships and by Vessel Traffic Services for identifying and locating vessels by electronically exchanging data with other nearby ships and VTS stations. Information such as unique identification, position, course,...
(AIS), a system used by ships and Vessel Traffic Services.
Theory of operation
ADS-B consists of three components:
- A transmitting subsystem that includes message generation and transmission functions at the source, e.g. airplane.
- The transport protocol, e.g. VHF (VDL mode 2 or 4),1090ES, or 978MHz UAT.
- A receiving subsystem that includes message reception and report assembly functions at the receiving destination, e.g. other airplanes, vehicle or ground system.
The source of the state vector and other transmitted information as well as user applications are not considered to be part of the ADS-B system.
Relationship to surveillance radar
RadarRadar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for RAdio Detection And...
directly measures the range and bearing of an aircraft from a ground-based
antennaAn antenna is a transducer designed to transmit or receive electromagnetic waves. In other words, antennas convert electromagnetic waves into electrical currents and vice versa. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless...
. Bearing is measured by the position of the rotating radar antenna when it receives a response to its interrogation from the aircraft, and range is measured by the time it takes for the radar to receive the interrogation response.
The antenna beam becomes wider as the aircraft gets further away, making the position information less accurate. Additionally, detecting changes in aircraft velocity requires several radar sweeps that are spaced several seconds apart. In contrast, a system using ADS-B creates and listens for periodic position and intent reports from aircraft. These reports are generated based on the global positioning system (GPS) and distributed via VHF radio or Mode S transponders, meaning integrity of the data is no longer susceptible to the position of the aircraft or the length of time between radar sweeps.
Primary Surveillance Radar does not require any cooperation from the aircraft. It is robust in the sense that surveillance outage failure modes are limited to those associated with the ground radar system.
Secondary Surveillance RadarSecondary surveillance radar is a radar system used in air traffic control , which not only detects and measures the position of aircraft but also requests additional information from the aircraft itself such as its identity and altitude...
depends on active replies from the aircraft. Its failure modes include the
transponderA transponder is an electronic device that produces a response when it receives a radio-frequency interrogation...
aboard the aircraft. Typical ADS-B aircraft installations use the output of the navigation unit for navigation and for cooperative surveillance, introducing a common
failure modeFailure causes are defects in design, process, quality, or part application, which are the underlying cause of the failure or which initiate a process which leads to failure....
that must be accommodated in air traffic surveillance systems.
| Type | Independent? | Cooperative? |
|---|
| Primary surveillance radar (PSR) |
Yes: surveillance data
derived by radar |
No: does not depend on
aircraft equipment |
Secondary surveillance radarSecondary surveillance radar is a radar system used in air traffic control , which not only detects and measures the position of aircraft but also requests additional information from the aircraft itself such as its identity and altitude...
(SSR) |
Yes: surveillance data
derived by radar |
Yes: requires aircraft to have
a working ATCRBS transponder |
| Automatic dependent surveillance (ADS-B) |
No: surveillance data
provided by aircraft |
Yes: requires aircraft to have
working ADS-B function |
| Source:DO-242A |
Today's
ATCAir traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
systems do not rely on coverage by a single radar. Instead a multiradar picture is presented via the ATC system's display to the controller (
ATCOAir traffic controllers are the people who operate the air traffic control systems to expedite and maintain a safe and orderly flow of air traffic and help prevent mid-air collisions. They apply separation rules to keep aircraft apart from each other in their area of responsibility and move all...
). This improves the quality of the reported position of the airplane, provides a measure of redundancy, and makes it possible to verify the output of the different radars against others. This verification can also use sensor data from other technologies, such as ADS-B and
multilaterationMultilateration, also known as hyperbolic positioning, is the process of locating an object by accurately computing the time difference of arrival of a signal emitted from that object to three or more receivers...
.
Relationship to ADS-A/ADS-C
There are two commonly recognized types of ADS for aircraft applications:
- ADS-Addressed (ADS-A), also known as ADS-Contract (ADS-C), and
- ADS-Broadcast (ADS-B).
ADS-B differs from ADS-A in that ADS-A is based on a negotiated one-to-one peer relationship between an aircraft providing ADS information and a ground facility requiring receipt of ADS messages. For example, ADS-A reports are employed in the Future Air Navigation System (
FANSAir Traffic Control's ability to monitor aircraft was being rapidly outpaced by the growth of flight as a mode of travel. In an effort to improve aviation communication, navigation, surveillance, and air traffic management ICAO standards for a future system were created, this integrated system is...
) using the Aircraft Communication Addressing and Reporting System (ACARS) as the communication protocol. During flight over areas without radar coverage (e.g. oceanic and polar), reports are periodically sent by an aircraft to the controlling air traffic region.
The transmission delay caused by protocol, satellites, etc., is significant enough that significant aircraft separations are required.
The cost of using the satellite channel leads to less frequent updates. Another drawback is that no other aircraft can benefit from the transmitted information.
Relationship to other broadcast services
The ADS-B link can be used to provide other broadcast services, such as TIS-B and FIS-B (see below).
Another potential aircraft-based broadcast capability is to transmit aircraft measurements of meteorological data.
Benefits of ADS-B
ADS-B is intended to increase safety and efficiency. Safety benefits include:
- Improved visual acquisition especially for general aviation
General aviation is one of two categories of civil aviation. It refers to all flights other than military and scheduled airline flights, both private and commercial. General aviation flights range from gliders and powered parachutes to large, non-scheduled cargo jet flights...
under visual flight rules (VFR).
- Reduced runway incursion
A runway incursion is an incident at an airport which adversely affects runway safety, defined by the International Civil Aviation Organization on April 27, 2006, as:...
s on the ground.
ADS-B enables increased capacity and efficiency by supporting:
- Enhanced visual approaches
- Closely spaced parallel approaches
- Reduced spacing on final approach
- Reduced aircraft separations
- Enhanced operations in high altitude airspace for the incremental evolution of the "free flight
Free flight is a developing air traffic control method that uses no centralized control . Instead, parts of airspace are reserved dynamically and automatically in a distributed way using computer communication to ensure the required separation between aircraft. This new system may be implemented...
" concept
- Surface operations in lower visibility conditions
- Near visual meteorological conditions (VMC
VMC can mean:*Visual meteorological conditions, in which visual-flight-rules flight is permitted*The VMC speed in aviation related to the critical engine*Vertical machining center, a vertical milling machine with CNC control...
) capacities throughout the airspace in most/all weather conditions
- Improved ATC
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
services in non-radar airspace
However, although ADS-B is suitable for surveillance of remote areas where the siting of radars is difficult, some ATC providers are not yet convinced that it is currently suitable for use in high traffic volume areas, such as in UK and Northern European airspace. Changing from conventional SSR to ADS-B would also require investment in ATC infrastructure, something which many European providers may be unwilling to sanction. Furthermore, ADS-B provides no ground verification of the accuracy of the information provided by aircraft and this could have adverse security implications.
Traffic information services-broadcast (TIS-B)
TIS-B supplements ADS-B air-to-air services to provide complete situational awareness in the cockpit of all traffic known to the ATC system. TIS-B is an important service for an ADS-B link in airspace where not all aircraft are transmitting ADS-B information. The ground TIS-B station transmits surveillance target information on the ADS-B data link for unequipped targets or targets transmitting only on another ADS-B link.
TIS-B uplinks are derived from the best available ground surveillance sources:
- ground radars for primary and secondary targets
- multi-lateration systems for targets on the airport surface
- ADS-B systems for targets equipped with a different ADS-B link
Multilink gateway service
The multilink gateway service is a companion to TIS-B for achieving interoperability in low altitude terminal airspace. In some airspaces, aircraft that primarily operate in high altitude airspace are equipped with 1090ES, and aircraft operating primarily in low altitude airspace are equipped with UAT. These aircraft cannot directly share air-to-air ADS-B data. In terminal areas, where both types of ADS-B link are in use, ADS-B/TIS-B ground stations use ground-to-air broadcasts to relay ADS-B reports received on one link to aircraft using the other link.
Flight information services-broadcast (FIS-B)
FIS-B provides weather text, weather graphics,
NOTAMNOTAM or NoTAM is the quasi-acronym for a "Notice To Airmen". NOTAMs are created and transmitted by government agencies under guidelines specified by Annex 15: Aeronautical Information Services of the Convention on International Civil Aviation. A NOTAM is filed with an aviation authority to alert...
s,
ATISAutomatic Terminal Information Service, or ATIS, is a continuous broadcast of recorded noncontrol information in busier terminal areas. ATIS broadcasts contain essential information, such as weather information, which runways are active, available approaches, and any other information required by...
, and similar information. FIS-B is inherently different from ADS-B in that it requires sources of data external to the aircraft or broadcasting unit, and has different performance requirements such as periodicity of broadcast.
In the US, FIS-B services will be provided over the UAT link in areas that have a ground surveillance infrastructure.
ADS-B physical layer
Three link solutions are being proposed as the physical layer for relaying the ADS-B position reports:
- 1090 MHz Mode S Extended Squitter (ES),
- Universal Access Transceiver (UAT) and
- VHF Data Link
The VHF Data Link or VHF Digital Link is a means of sending information between aircraft and ground stations . Aeronautical VHF data links use the band 117.975 - 137 MHz assigned by the International Telecommunication Union to Aeronautical Mobile Route Services...
(VDL) Mode 4.
A comparison of these link solutions was made in Gatwick/Heathrow in year 2002 for the Eurocontrol ADS programme.
1090ES
In 2002, the FAA announced a dual link decision using 1090 MHz ES and UAT as media for the ADS-B system in the United States, with the 1090 MHz extended squitter ADS-B link for air carrier and private/commercial operators of high performance aircraft, and Universal Access Transceiver (UAT) ADS-B link for the typical general aviation user.
Europe has not officially chosen a physical layer for ADS-B. A number of technologies are in use. However, the influential Eurocontrol CASCADE program uses 1090ES exclusively.
With 1090ES, the existing Mode S transponder (TSO C-112 or a stand alone 1090 MHz transmitter) supports a message type known as the extended squitter (ES) message. It is a periodic message that provides position, velocity, time, and, in the future, intent. The basic ES does not offer intent since current flight management systems do not provide such data – called trajectory change points. To enable an aircraft to send an extended squitter message, the transponder is modified (TSO C-166A) and aircraft position and other status information is routed to the transponder. ATC ground stations and TCAS-equipped aircraft already have the necessary 1090 MHz (Mode S) receivers to receive these signals, and would only require enhancements to accept and process the additional Extended Squitter information. 1090ES does not support FIS-B service.
Universal access transceiver
The UAT system is specifically designed for ADS-B operation. Because UAT is more flexible and has greater bandwidth, many Air Traffic management experts think that UAT will become the dominant ADS-B link standard within the next ten years. UAT is also the first link to be certified for "radar-like" ATC services in the U.S. Since 2001, it has been providing 5 nm enroute separation (the same as radar) in Alaska. UAT is the only ADS-B link standard that is truly bi-directional: UAT users have access to ground-based aeronautical data and can receive reports from proximate traffic (FIS-B and TIS-B, which provides reports for proximate aircraft through a multilink gateway service that provides ADS-B reports for 1090ES equipped aircraft and non-ADS-B equipped Radar traffic. UAT equipped aircraft can also "see" each other with accuracy and range that exceeds even TCAS. Viable ADS-B UAT networks now exist on the US East Coast, Alaska and Oregon. Since 2006, a US company has been helping the Civil Aviation Flight University of China run the largest ADS-B system in the world - a network that spans more than 1,200 nm across Central China.
VDL mode 4
The VDL Mode 4 system could utilize one or more of the existing aeronautical VHF frequencies as the radio frequency physical layer for ADS-B transmissions.
VDL Mode 4 uses a protocol (STDMA, invented by
SwedishSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe...
Håkan LansAnders Håkan Lans is a Swedish inventor who invented the graphic processor for colour computer graphics . He has also designed a digitizer cursor for a Graphics tablet....
in 1988) that allows it to be self-organizing, meaning no master ground station is required.
In November 2001 this protocol was published by ICAO as a global standard.
This medium is best used for short message transmissions between a large number of users.
VDL Mode 4 systems required by airlines in Europe as a mean for more efficient ATC service
.
ADS-B supported applications
The ADS-B data link supports a number of airborne and ground applications. Each application has its own operational concepts, algorithms, procedures, standards, and user training.
Cockpit display of traffic information
A Cockpit Display of Traffic Information (CDTI) is a generic display that provides the flight crew with surveillance information about other aircraft, including their position. Traffic information for a CDTI may be obtained from one or multiple sources, including ADS-B, TCAS, and TIS-B. Direct air-to-air transmission of ADS-B messages supports display of proximate aircraft on a CDTI.
In addition to traffic based on ADS-B reports, a CDTI function might also display current weather conditions, terrain, airspace structure, obstructions, detailed airport maps, and other information relevant to the particular phase of flight.
Airborne collision avoidance
ADS-B is seen as a valuable technology to enhance
ACASAirborne Collision Avoidance System is an ICAO standard specified in ICAO Annex 10 Vol IV which provides pilots with a system independent of air traffic control to detect the presence of other aircraft which may present a threat of collision...
operation. Incorporation of ADS-B can provide benefits such as:
- Decreasing the number of active interrogations required by ACAS, thus increasing effective range in high density airspace.
- Reducing unnecessary alarm rate by incorporating the ADS-B state vector, aircraft intent, and other information.
- Use of the ACAS display as a CDTI, providing positive identification of traffic.
- Extending collision avoidance below 1000 feet above ground level, and detecting runway incursions.
Eventually, the ACAS function may be provided based solely on ADS-B, without requiring active interrogations of other aircraft transponders.
Other applications
Other applications that may benefit from ADS-B include:
- Improved search and rescue
Search and rescue is the search for and provision of aid to people who are in distress or imminent danger.-Definitions of Search and Rescue:There are many different definitions of search and rescue, depending on the agency involved....
- Enhanced flight following
- Lighting control and operation
- Airport ground vehicle and aircraft rescue and firefighting vehicle operational needs
- Altitude height keeping performance measurements
- General aviation
General aviation is one of two categories of civil aviation. It refers to all flights other than military and scheduled airline flights, both private and commercial. General aviation flights range from gliders and powered parachutes to large, non-scheduled cargo jet flights...
operations control
U.S. implementation timetable
The U.S. FAA ADS-B implementation is broken into three segments each with a corresponding time line. Ground segment implementation and deployment is expected to begin in 2009 and be completed by 2013 throughout the National Airspace System. Airborne equipage is user driven and is expected to be completed both voluntarily based on perceived benefits and through regulatory actions (Rulemaking) by the FAA. The cost to equip with ADS-B Out capability is relatively small and would benefit the airspace with surveillance in areas not currently served by radar. The FAA intends to provide similar service within the NAS to what radar is currently providing (5NM en route and 3NM terminal radar standards) as a first step to implementation. However, ADS-B In capability is viewed as the most likely way to improve NAS throughput and enhance capacity.
In December 2008 Acting FAA Administrator Robert Sturgell gave the go-ahead for ADS-B to go live in southern Florida. The south Florida installation, which consists of 11 ground stations and supporting equipment, is the first commissioned in the USA, although developmental systems have been online in Alaska and along the East Coast. The completed system will consist of 794 ground station transceivers. The December 2008 action is in compliance with a late-term
Executive OrderAn executive order in the United States is an order issued by the President, the head of the executive branch of the federal government. In other countries, similar edicts may be known as decrees, or orders-in-council. Executive orders may also be issued at the state level by a state's Governor. U.S...
from
George W. BushGeorge Walker Bush was the 43rd President of the United States from 2001 to 2009 and the 46th Governor of Texas from 1995 to 2000....
which mandated accelerated approval of NextGen.
FAA segment 1 (2006-2009)
ADS-B deployment and voluntary equipage, along with rule making activities. Pockets of development will exploit equipment deployment in the areas that will provide proof of concept for integration to ATC automation systems deployed in the NAS.
FAA segment 2 (2010-2014)
ADS-B ground stations will be deployed throughout the NAS, with an In-Service Decision due in the 2012-13 time frame. Completed deployment will occur in the 2013-2014 time frame. Equipage is expected to begin after the proposed rule is finalized in around 2010:
- Airport Situational Awareness – A combination of detailed airport maps, airport multilateration systems, ADS-B systems and enhanced aircraft displays have the potential to significantly improve Airport Surface Situational Awareness (ASSA) and Final Approach and Runway Occupancy Awareness (FAROA).
- Oceanic In-trail – ADS-B may provide enhanced situational awareness and safety for Oceanic In-trail maneuvers as additional aircraft become equipped.
- Gulf of Mexico – In the Gulf of Mexico, where ATC radar coverage is incomplete, the FAA is locating ADS-B (1090 MHz) receivers on oil rigs to relay information received from aircraft equipped with ADS-B extended squitters back to the Houston Center to expand and improve surveillance coverage.
FAA segment 3 (2015-2020)
ADS-B In equipage will be based on user perceived benefit, but is expected to be providing increased situational awareness and efficiency benefits within this segment. Those aircraft who choose to equip in advance of any mandate will see benefits associated with preferential routes and specific applications. Limited radar decommissioning will begin in the time frame with an ultimate goal of a 50% reduction in the Secondary Surveillance Radar infrastructure.
Non FAA implementations
- Use of ADS-B and CDTI may allow decreased approach spacing at certain airports to improve capacity during reduced-visibility operations when visual approach operations would normally be terminated (eg. ceilings less than MVA +500).
- United States
- Cargo Airline Association - Cargo carriers, notably United Parcel Service
United Parcel Service, Inc. , commonly referred to as UPS, is the world's largest package delivery company. Headquartered in Sandy Springs, Georgia, United States, UPS delivers more than 15 million packages a day to 6.1 million customers in more than 200 countries and territories around the world...
(UPS), operating at their hub airports operate largely at night. Much of the benefit to these carriers is envisioned through merging and spacing the arriving and departing traffic to a more manageable flow. More environmentally friendly and efficient area navigationArea Navigation is a method of air navigation that allows an aircraft to choose any course within a network of navigation beacons, rather than navigating directly to and from the beacons...
(RNAV) descent profiles, combined with CDTICDTI is an abbreviation for:* Common rail Diesel Turbo Injection - a series of engines used in Opel and Vauxhall cars - the 1.3 and 1.9 litre variants are produced by Fiat-GM Powertrain, the 1.7 litre variant by Isuzu....
, may allow crews to eventually aid controllers with assisted visual acquisition of traffic and limited cockpit-based separation of aircraft. The benefits to the carrier are fuel and time efficiencies associated with idle descent and shorter traffic patterns than typical radar vectoring allows.
- Embry-Riddle Aeronautical University
Embry-Riddle Aeronautical University is a private, coeducational university with a history dating from the early days of aviation. Students are enrolled in one of two residential campuses located in Daytona Beach, Florida and Prescott, Arizona or in Embry-Riddle Worldwide, composed of over 130...
- ERAU has equipped their training aircraft at its two main campuses in Florida and Arizona with UAT ADS-B capability as a situational safety enhancement. The University has been doing this since May 2003, making it the first use in general aviation. With the addition of the G1000 to their fleet in 2006, ERAU became the first fleet to combine a glass cockpit with ADS-B.
- University of North Dakota
The University of North Dakota is a public university in Grand Forks, North Dakota, USA. Established by the Dakota Territorial Assembly in 1883, six years before the establishment of the state of North Dakota, UND is the oldest university in the state and enrolls over 13,100 students. UND was...
- UND has received an FAA grant to test ADS-B, and has begun to outfit their Piper Warrior fleet with an ADS-B package.
- China - An American Company, ADS-B Technologies created one of the largest and most successful ADS-B system in the world (an 8 station, 350+ aircraft network that spans more than 1,200 nm across Central China). This was also the first UAT installation outside the U.S.. As of March, 2009, more than 1.2M incident/failure free flight hours have been flown with these ADS-B systems.
- Australia - Upper Airspace Program - A program aimed at providing near-term safety and operational benefits in high level, non-radar airspace. Includes installation of approximately 28 ADS-B ground stations, strategically located across Australia to provide air traffic surveillance above 30,000 feet in continental airspace outside of radar coverage. All sites are expected to be installed and operating by mid 2007.
- Australian Transition to Satellite Technology - Now in initial planning and development, this is a major, longer term program designed to make ADS-B the primary means of ground to air and air to air surveillance in Australian en route airspace. Includes installation of additional ADS-B ground stations to provide air traffic surveillance in airspace currently covered by en route radar facilities. Intended to lead to the decommissioning of a number of radar sites. Mandatory aircraft ADS-B equipment requirements will apply – funding options to support general aviation operators will be explored.
- Canada - Canada
Canada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean...
is planning to use ADS-B to provide coverage of its northern airspace around Hudson Bay, most of which currently has no radar coverage. ADS-B will be initially deployed in the Hudson BayHudson Bay is a large body of water in northeastern Canada. It drains a very large area that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota, and Montana. A smaller offshoot of the bay,...
Basin in 2007–2008 and the service is expected to be later extended to cover the rest of the Canadian Arctic and eventually to the rest of Canada.
As of November 2008, Nav Canada has installed five ADS-B ground-station receivers around Hudson Bay, which will go into daily use in January.
- Sweden - LFV Group in Sweden has implemented a nationwide ADS-B network with 12 ground stations. Installation commenced during spring 2006, and the network was fully (technically) operational in 2007. An ADS-B supported system is planned for operational usage in Kiruna during spring 2009. Based on the VDL Mode 4 standards, the network of ground stations can support services for ADS-B, TIS-B, FIS-B, GNS-B (DGNSS augmentation) and Point-to-Point communication, allowing aircraft equipped with VDL 4-compliant transceivers to lower fuel consumption and reduce flight times.
System design considerations of ADS-B
A concern for any ADS-B protocol is the capacity for carrying ADS-B messages from aircraft, as well as allowing the radio channel to continue to support any legacy services. For 1090ES, each ADS-B message is composed of a pair of data packets. The greater the number of packets transmitted from one aircraft, the lesser the number of aircraft that can participate in the system, due to the fixed and limited channel data bandwidth.
System capacity is defined by establishing a criterion for what the worst environment is likely to be, then making that a minimum requirement for system capacity. For 1090ES, both TCAS and ATCRBS/
MSSRSecondary surveillance radar is a radar system used in air traffic control , which not only detects and measures the position of aircraft but also requests additional information from the aircraft itself such as its identity and altitude...
are existing users of the channel. 1090ES ADS-B must not reduce capacity of these existing systems.
The FAA national program office and other International aviation regulators are addressing concerns about ADS-B
non-secure nature of ADS-B transmissions. ADS-B messages can be used to know the location of an aircraft, and there is no means to guarantee that this information is not used inappropriately. Additionally, there are some concerns about the integrity of ADS-B transmissions. ADS-B messages can be produced, with simple low cost measures, which spoof the locations of multiple phantom aircraft to disrupt safe air travel. There is no foolproof means to guarantee integrity, but there are means to monitor for this type of activity. This problem is however similar to the usage of ATCRBS/
MSSRSecondary surveillance radar is a radar system used in air traffic control , which not only detects and measures the position of aircraft but also requests additional information from the aircraft itself such as its identity and altitude...
where false signals also are potentialy dangerous (uncorrelated secondary tracks).
There are some concerns about ADS-B dependence on other systems. This paper from 2001 mentions some of the potential risks.
The risks mentioned can be mitigated by using other sources of information, e.g.
GLONASSGLONASS is a radio-based satellite navigation system, developed by the former Soviet Union and now operated for the Russian government by the Russian Space Forces.It is an alternative and complementary to the United States' Global Positioning System , the Chinese Compass...
, Galileo or
multilaterationMultilateration, also known as hyperbolic positioning, is the process of locating an object by accurately computing the time difference of arrival of a signal emitted from that object to three or more receivers...
.
There are some General Aviation concerns that ADS-B removes anonymity of the VFR aircraft operations. The ICAO 24-bit
transponderA transponder is an electronic device that produces a response when it receives a radio-frequency interrogation...
code specifically assigned to each aircraft will allow monitoring of that aircraft when within the service volumes of the Mode-S/ADS-B system. Unlike the Mode A/C transponders, there is no code "1200"/"7000", which offers casual anonymity. Mode-S/ADS-B identifies the aircraft uniquely among all in the world, in a similar fashion as a MAC number for an ethernet card or the IMEI (International Mobile Equipment Identity) of a GSM phone.
Public Access to ADS-B
Currently there are no laws preventing the public from listening to and decoding ADS-B transmissions. Like Cellular Phone however, laws can easily be implemented to make reception a crime, and receivers would then become contraband. The ongoing debate amongst hobbyists is to display real-time activity on personal screens and then delay five minutes on networked displays. Others feel that, like GPS data, it should be freely available.
Two receivers are currently popular, although both are at the expensive end for consumer devices. The first on the market was Kinetic Avionics with their SBS-1. The second was the
AirNav Systems RadarBox- RadarBox Mode S Decoder :A Windows PC software and hardware package which allows appropriately equipped aircraft to be seen on a simulated radar screen. A small receiver connects to the PC via USB and aircraft are detected using the small supplied antenna...
. Both of these devices are designed to be used for portable operation, although many use them in a fixed base setting. They are both supplied with a short USB cable for interface to a Windows PC, and a short coax to a small omni antenna.
Both products have specialized single-use receivers in them. Unlike most radios there is no
Intermediate FrequencyIn communications and electronic engineering, an intermediate frequency is a frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called...
(IF). The ADS-B data flows from the supplied antenna through an LNA pre-amp. It is bandwidth filtered, and then the pulses are extracted using a logarithmic amplifier chip. This chip can operate directly at the ADS-B frequency of 1090 MHz. These analog pulses are then applied to a high speed analog to digital (A/D) converter (40 MHz for Kinetic, 8 MHz for AirNav) and then on to the
Field-Programmable Gate ArrayA field-programmable gate array is an integrated circuit designed to be configured by the customer or designer after manufacturing—hence "field-programmable"...
(FPGA) for Kinetic, or Microcontroller for AirNav, where the Mode-S frames are detected. The detected Mode-S packets are then sent to the PC via a USB interface or, in the case of an SBS-1, through an optional ethernet interface module. The AirNav microcontroller passes most of the downlink formats (not all), while the SBS-1 FPGA only processes six downlink formats.
A visualisation of publicly available ADS-B hardware is the site http://www.flygradar.se, showing information from 10+ ADS-B base stations in
SwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe...
overlayed onto
Google MapsGoogle Maps is a web mapping service application and technology provided by Google, free , that powers many map-based services, including the Google Maps website, Google Ride Finder, Google Transit, and maps embedded on third-party websites via the Google Maps API...
.
ADS-B technical and regulatory documents
MASPS = Minimum Aviation System Performance Standards
MOPS = Minimum Operational Performance Standards
- DO-289 - Airborne Surveillance Applications (ASA) MOPS
- High level system architecture and sub-system descriptions.
- DO-242A
DO-242A is an aviation system standard published by RTCA, Incorporated. It contains minimum aviation system performance standards for Automatic Dependent Surveillance-Broadcast...
- ADS-B MASPS
- Describes system-wide operational use of ADS-B.
- DO-286A - TIS-B MASPS
- Describes a surveillance service that derives traffic information from ground surveillance sources, broadcasts to ADS-B equipped aircraft or surface vehicles.
- DO-260A - 1090 MOPS for ADS-B and TIS-B
- Airborne equipment characteristics / requirements for 1090 MHz Mode-S extended squitter.
- Change 1-DO-260A–PMC consideration review/approval –June 27 2006
- DO-282A - UAT MOPS
- Airborne equipment characteristics / requirements utilizing the universal access transceiver.
- DO-XXX - STP MOPS (work in progress)
- Describes a function that processes information prior to the information being broadcast by the ADS-B transmit function.
- DO-XXX - ASAS MOPS (work in progress)
- Adds additional subsystems necessary to fully implement AirborneSurveillance Applications:
- Airborne Surveillance and Separation Assurance Processing (ASSAP)
- Cockpit Display of Traffic Information (CDTI)
- DO-259 - CDTI Application Description
- Provides initial CDTI applications descriptions.
See also
- DO-212
DO-212 is a performance standard published by RTCA, Incorporated. It contains Minimum Operational Performance Standards for aircraft equipment required for the Automatic Dependent Surveillance function...
Minimal Operational Performance Standards for Airborne Automatic Dependent Surveillance (ADS) Equipment
- NextGen (US)
- Single European Sky ATM Research
SESAR or Single European Sky ATM Research is the name given to the project which is set to completely overhaul the European airspace.The SESAR project is composed of three phases:...
- TCAS
- FLARM
FLARM is an electronic device to selectively alert pilots to potential collisions between aircraft.FLARM obtains its position from an integral GPS and a barometric sensor and then broadcasts this with forecast data about the future 3d flight track...
- PCAS
PCAS can stand for:*Personal Carbon Allowances, rations of allowed carbon emissions for individuals, designed to help address human-caused global warming* Planet-Crossing Asteroid Survey* Polytechnics Central Admissions Service...
- ASDE-X
Airport Surface Detection Equipment, Model X, or ASDE-X, is a runway-safety tool that enables air traffic controllers to detect potential runway conflicts by providing detailed coverage of movement on runways and taxiways...
- Free flight
Free flight is a developing air traffic control method that uses no centralized control . Instead, parts of airspace are reserved dynamically and automatically in a distributed way using computer communication to ensure the required separation between aircraft. This new system may be implemented...
External links
Commercial implementations of ADS-B