How does ADS-B work?

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ADS-B is becoming an increasingly important surveillance technology for much of the global aviation industry and has played a large part in increasing safety, improving efficiency and reducing costs for the sector

In this article, we’ll take a closer look at how ADS-B works and highlight some factors to consider when transitioning to this system of surveillance.

What does ADS-B stand for?

ADS-B stands for Automatic Dependent Surveillance – Broadcast. It’s defined as automatic because it periodically transmits information without the need for pilot or operator involvement. It’s dependent on GPS or other suitable navigation systems, such as a Flight Management System (FMS), for position and velocity vectors, and is considered surveillance because of the method of determining 3D position and identification of aircraft and other objects. The information the system transmits, such as aircraft position, altitude, velocity and callsign, is available to anyone with suitable receiving equipment. This makes it a useful tool for aircraft operators and air traffic controllers globally in navigating the increasingly busy airspace.

How does ADS-B work?

ADS-B infographic

ADS-B provides aircraft surveillance data that can be used by Air Traffic Management and other aircraft, to track the position of an aircraft in the airspace at any given time. ADS-B tracking relies on a Mode S 1090ES transponder, Global Navigation Satellite System (GNSS) and the deployment of ground or satellite based surveillance systems.

Aircraft equipped with ADS-B  OUT systems transmit data using the 1090MHz frequency via squitters – burst transmissions sent periodically by the Mode S transponder. This data can be received by air traffic controllers, and other aircraft that are fitted with transponders with ADS-B IN capability.

1090MHz is the internationally approved frequency to transmit Mode-S replies and ADS-B data. In certain airspace, specifically the US, aircraft flying under 18,000 FT MSL can broadcast data using the 978MHz – the Universal Access Transceiver (UAT) – frequency. This is largely due to the high volume of general aviation aircraft that fly in the US airspace compared to other regions. Both 1090MHz and 978MHz channels can receive traffic (TIS-B) and weather (FIS-B) data.

What are the requirements for ADS-B?

From a practical perspective, for aircraft to use ADS-B, they need to be equipped with a Mode-S transponder or ADS-B beacon that enables ADS-B OUT. This allows the aircraft to broadcast data to ground stations, ADS-B capable satellites, and other aircraft. To receive data, an aircraft also needs to be fitted with ADS-B IN capabilities which would allow functionalities like situational awareness, radar gap filler etc.

ADS-B is currently being implemented in airspaces around the world, and the 1090 MHz Mode-S Extended Squitter technology is used to ensure global interoperability. ADS-B Standards are being jointly developed by the RTCA and the European Organisation for Civil Aviation Equipment (EUROCAE) in order to maintain interoperability worldwide.

Since June 2020, the regulations in Europe and the USA require all general air traffic to be compliant with elementary Mode S Elementary Surveillance. Aircraft with maximum Take-Off Mass greater than 5700kg, or maximum cruising True Air Speed greater than 250 kts, must be compliant with both Mode S Enhanced Surveillance and ADS-B OUT requirements.

Why is ADS-B becoming an increasingly important surveillance technology?

ADS-B is becoming a widely mandated surveillance technology for a number of reasons. It also has a number of benefits versus other methods of surveillance that were considered, specifically compared to radar replacement and multilateration.

All three systems offer core surveillance, ADS-B offers additional cockpit advisory services (e.g. traffic and weather information products to improve pilots’ situational awareness). ADS-B system also supports air-to-air applications. This ability to transmit data between aircraft is one of the crucial systems that enable efficient and safe spacing between aircraft.

ADS-B provides much better visibility regardless of the terrain. Radar signals cannot travel long distances or penetrate solid objects. This is because radio waves are limited to line of sight. Aircraft transmit the position no matter where it is, and this position is then received by ground receiver or better by satellites, which helps the ADS-B system to be very effective even when flying over difficult terrain.

Unlike ground-based radar towers, satellite-based ADS-B receivers are able to provide coverage across the globe without interruption, 24/7, regardless of the terrain. They can relay data in areas that would normally be hard to reach by radar, such as large bodies of water and mountainous terrain. Given that 71% of the earth’s surface is water and around 25% mountains, the ability to provide coverage irrespective of this terrain means ADS-B offers a much greater advantage over radar signals.

Radar ADS-B infographic

The cost of implementing ADS-B globally is also much lower than traditional radars, as the combination of ground-based ADS-B receivers and nanosatellites are economical. By enabling enhanced coverage at a lower cost, it’s clear that ADS-B tracking is the most effective surveillance technology for the aviation industry today.

Why is ADS-B useful?

ADS-B tracking has become an essential part of modern aviation, as it enables pilots to have a much clearer picture of the skies around an aircraft, quickly alerting them to potential obstacles – such as other aircraft, or severe weather events. As air traffic has increased, the need for more information about the air situation has also increased. This supports both passenger safety, but also cost saving and reduced emissions. As a result of the increased use of ADS-B tracking, reduced separation of aircraft is currently being tested in Australia and the North Atlantic. If successful, aircraft with ADS-B could be subject to reduced separation, thus allowing for more optimal and cost-effective routes in future.

How can Spire help with ADS-B data requirements?

Spire is a provider of global flight tracking data. We offer access to both historical and up-to-date flight and weather data to support aviation operations. Our satellite-based receivers enable us to capture data, via ADS-B, even in remote areas that terrestrial services cannot, such as large bodies of water or mountain ranges. This means we can provide better global coverage, 24/7.

Global coverage for better solutions

Limited visibility with terrestrial data

Limited visibility with terrestrial data

Global coverage with satellite ADS-B

Global coverage with satellite ADS-B

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Having access to more data means Spire customers can make more strategic business decisions, faster. With our flight tracking and air traffic APIs, you can quickly integrate and query data using any tools that fit your workflows.

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