Flightradar24 is a global flight tracking service that shows live air traffic from around the world, but how does it actually work?
We combine data from several data sources including ADS-B, MLAT, satellite, and various radar data. This positional data is aggregated with schedule and flight status data to create the flight tracking experience you get on www.flightradar24.com and in the Flightradar24 app. Let’s take a look at those methods of tracking in more detail.
ADS-B
The primary technology that Flightradar24 uses to receive flight information is called automatic dependent surveillance-broadcast (ADS-B). Introduced several decades ago, ADS-B usage has grown steadily as various mandates requiring updated transponders have come into force in places like the United States, Canada, Europe, and Australia. ADS-B technology is the long-term air traffic management replacement for radar technologies, especially in areas with limited radar coverage, such as remote areas and oceanic airspace.
Aircraft broadcast a series of datapoints at regular intervals, including data on their position, altitude, speed, and much more. These signals are received by our network of ADS-B ground receivers, the largest such independent network in the world.
The process
- The ADS-B transponder transmits a signal containing the position of the aircraft (and much more)
- ADS-B signal is picked up by a receiver connected to Flightradar24’s network
- Receiver sends data to Flightradar24
- Data is shown on www.flightradar24.com and in Flightradar24 apps
MLAT tracking
In regions with coverage from several Flightradar24 receivers we also calculate positions of non-ADS-B equipped aircraft with the help of Multilateration (MLAT), by using a method known as Time Difference of Arrival (TDOA).
By measuring the time it takes to receive the signal from aircraft with an older Mode S transponder, it’s possible to calculate the position of these aircraft. We have recently improved our MLAT calculations reducing the the number of receivers required for MLAT from four to three. Because three or more receivers are needed to calculate the aircraft’s position, this can only be achieved at higher altitudes or in areas with many receivers. MLAT comes in especially handy when aircraft fly through areas of GPS jamming or spoofing, as we can calculate a position until the aircraft is no longer experiencing interference.
Satellite tracking
Satellite-based flight tracking is the latest step in our quest for global ADS-B coverage. Satellites equipped with ADS-B receivers collect data from aircraft outside our terrestrial ADS-B network’s coverage area and send that data to the Flightradar24 network. Satellite-based ADS-B data available on Flightradar24 comes from multiple providers. As the number of satellites supplying data and their location are dynamic, satellite coverage varies. Generally, satellite-based ADS-B increases coverage of flights over the ocean where ground-based reception is not possible. Only aircraft equipped with an ADS-B transponder may be tracked via satellite at this time.
Other sources of data
Radar Data in North America and Australia
In addition to ADS-B, MLAT, and satellite, we also receive additional live data for flights in North America. This data is based on multiple official sources, including radar data (not just aircraft equipped with ADS-B transponders) and includes most scheduled and commercial air traffic in US and Canadian airspace, as well as parts of the Atlantic and Pacific Oceans. Similarly, we receive additional radar data for air traffic in Australia. This data helps increase our coverage over Australia as well as parts of the Indian and Pacific Oceans.
Open Glider Network
Tracking data for gliders and other light aircraft comes from the Open Glider Network (OGN). It’s a project that has the goal to provide a unified tracking platform for gliders, drones and other small aircraft. Currently focused on tracking aircraft equipped with FLARM and OGN trackers, but also accepting other data sources such as SPOT, FANET, etc. As a simpler form of tracking, systems such a FLARM often do not provide select information, such as altitude.
Estimations
When an aircraft is flying out of coverage, Flightradar24 can estimate the position of the aircraft for up to 4 hours if the destination of the flight is known. For aircraft without a known destination, positions are estimated for up to 10 minutes. You can customize how long aircraft out of coverage are estimated on the map under Settings. Estimations are displayed with a black trail on the map.
