Just installed an ADS-B receiver from FlightRadar24.com by becoming one of their ADS-B and MLAT receiving stations. I will be updating this post with information on how it goes in the future. but for now, its looking good, uploading data (which combines sources using ADS-B, MLAT and FAA) to their servers every few seconds, from a small antenna and GPS head which I have installed on my chimney.
How it works
Flightradar24 is a flight tracker that shows live air traffic from around the world. Flightradar24 combines data from several data sources including ADS-B, MLAT and FAA. The ADS-B, MLAT and FAA data is aggregated together with schedule and flight status data from airlines and airports.
The primary technology that Flightradar24 use to receive flight information is called automatic dependent surveillance-broadcast (ADS-B).
- Aircraft gets its location from a GPS navigation source (satellite)
- The ADS-B transponder on aircraft transmits signal containing the location (and much more)
- ADS-B signal is picked up by a receiver connected to Flightradar24
- Receiver feeds data to Flightradar24
- Data is shown on flightradar24.com and in Flightradar24 apps
ADS-B is a relatively new technology under development, which means that today it’s rarely used by Air Traffic Control (ATC). Our estimations show that roughly 70% of all commercial passenger aircraft (75% in Europe, 55% in the US) are equipped with an ADS-B transponder. For general aviation this number is probably below 20%. The percentage of aircraft equipped with ADS-B receivers is steadily increasing though, as they will become mandatory for most aircraft around the world by 2020. When mandatory, ADS-B will replace primary radar as the primary surveillance method used by ATC.
Due to the high frequency used (1090 MHz) the coverage from each receiver is limited to about 250-450 km (150-250 miles) in all directions depending on location. The farther away from the receiver an aircraft is flying, the higher it must fly to be covered by the receiver. The distance limit makes it very difficult to get ADS-B coverage over oceans.
About 99% of Europe is covered with ADS-B receivers. There is also good ADS-B coverage in USA, Canada, Mexico, Caribbean, Brazil, Russia, Middle East, India, Japan, Thailand, Malaysia, Indonesia, Australia and New Zealand. In other parts of the world the ADS-B coverage varies.
In some regions it is possible to 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 the time it takes to receive the signal from aircraft with an older ModeS-transponder, it’s possible to calculate the position of these aircraft. Four FR24-receivers or more, receiving signals from the same aircraft, are needed to make MLAT work. MLAT coverage can only be achieved above about 5,000-10,000 feet as the probability that four or more receivers can receive the transponder signal increases with increased altitude.
Most parts of Europe and North America are today covered with MLAT above about 5,000-10,000 feet. There is also some MLAT coverage in Mexico, Brazil, South Africa, Japan, Taiwan, Thailand, Malaysia, Indonesia, Australia and New Zealand.
In addition to ADS-B and MLAT data, you can get data from the Federal Aviation Administration (FAA) in the United States. Unlike the ADS-B and MLAT data that is presented in real-time, the FAA data is delayed by roughly 5 minutes due to FAA regulations.
FAA data is based on radar data (i.e. not just planes with ADS-B transponders) and includes most scheduled and commercial air traffic in US and Canadian air space as well as parts of the Atlantic and Pacific Ocean.
Flarm is simpler version of ADS-B with a shorter range, primary used by smaller aircraft, in most cases gliders. The range of a Flarm receiver is between 20 and 100 km. Flarm receivers are often installed on small airports with a lot glider traffic to track the gliders around the airport. Read more about Flarm onWikipedia
Aircraft visible on Flightradar24 (within ADS-B coverage)
When ADS-B was initially launched, it was primarily used in commercial passenger aircraft with 100+ passengers. An increasing number of aircraft including smaller aircraft types, are getting ADS-B transponders but, until ADS-B becomes mandatory it’s up to the aircraft producer and owner to decide if an ADS-B transponder should be installed or not.
Common aircraft models that usually have an ADS-B transponder and are visible (within ADS-B coverage):
- All Airbus models (A300, A310, A318, A319, A320, A321, A330, A340, A350, A380)
- Antonov AN-148 and AN-158
- ATR 72-600 (most new deliveries)
- BAe ATP
- BAe Avro RJ70, RJ85, RJ100
- Boeing 737, 747, 757, 767, 777, 787
- Bombardier CS100 and CS300
- Embraer E190 (most new deliveries)
- Fokker 70 and 100
- McDonnell Douglas DC-10 and MD-11
- Sukhoi SuperJet 100
- Some newer Ilyushin and Tupolev (for example Il-96 and TU-204)
Common aircraft models that usually do not have an ADS-B transponder and are not visible on Flightradar24 (within ADS-B coverage):
- “Air Force One”
- Antonov AN-124 and AN-225
- ATR 42, 72 (except most new deliveries of ATR 72-600)
- Boeing 707, 717, 727, 737-200, 747-100, 747-200, 747SP
- BAe Jetstream 31 and 32
- All Bombardier CRJ models
- All Bombardier Dash models
- All CASA models
- All Dornier models
- All Embraer models (except most new deliveries of Embraer E190)
- De Havilland Canada DHC-6 Twin Otter
- Fokker 50
- McDonnell Douglas DC-9, MD-8x, MD-90
- Saab 340 and 2000
- Most helicopters
- Most older aircraft
- Most business jets
- Most military aircraft
- Most propeller aircraft
Of course there are lots of exceptions from these rules. There are some older A300, A310, A320, B737, B747, B757, B767, MD10, MD11 aircraft flying without an ADS-B transponder, which make those aircraft invisible when in areas with ADS-B coverage only. But there are also some Twin Otters, Saab 340, Saab 2000 and MD-80 aircraft with an ADS-B transponder that are visible in areas with ADS-B coverage.
Aircraft visible on Flightradar24 (within MLAT, FAA or Flarm coverage)
In regions with MLAT, FAA or Flarm coverage most of the air traffic is tracked and visible independent of aircraft type. That includes propeller aircraft, helicopters and gliders. But as mentioned above, MLAT coverage is limited to some areas with many FR24-receivers and can normally only be achieved at altitudes above about 5,000-10,000 feet, which means that general aviation at lower altitudes may be flying below MLAT coverage. The FAA is in most cases not tracking general aviation flights without a flight plan. Data provided by the FAA is often missing aircraft registration information and aircraft tracked with MLAT in many cases are missing the callsign information.
The GPS Head when it arrived, now installed on top of the Chimney
The antenna installed on my Chimney
The ADS-B Receiver
The back of the ADS-B receiver, showing the antenna, GPS, Network and power inputs
Errm, well lots of em!