Search

Understanding Extended Mode S Data in Flightradar24

Share this article

With the release of the latest version of the Flightradar24 website we introduced new flight details called Extended Mode S data. We’re proud to be the first flight tracking service to offer this additional flight data. We receive the Extended Mode S data directly from the aircraft we are tracking and decode the data for display on the website. Extended Mode S data can include additional information about the speed and altitude of the aircraft as well as weather information. Extended Mode S data is available to subscribers with a Gold or Business subscription.

 

Speed

Extended Mode S speed data, including Indicated Airspeed, True Airspeed, and Mach.
Extended Mode S speed data, including Indicated Airspeed, True Airspeed, and Mach.

Extended Mode S speed data can include values for Indicated Airspeed, True Airspeed, and Mach. Not every aircraft broadcasts each value. Airspeed values differ from ground speed, which is displayed on Flightradar24 for every aircraft tracked, as they measure the aircraft’s speed through an air mass rather than how quickly it is moving over the ground.

Indicated Airspeed is provided by the aptly named airspeed indicator and is a pressure-derived value. Indicated Airspeed is relied upon for important reference points, such as takeoff, approach, and landing speeds. Used primarily in the cruise portion of flight for navigation purposes, true airspeed is the speed of the aircraft relative to the air mass through which it is flying. The true airspeed value takes the density of the air mass in which the aircraft is flying into account, as opposed to Indicated Airspeed, which assumes sea level atmospheric conditions. The Mach number is the speed of the aircraft relative to the speed of sound in current conditions, which changes based on pressure and temperature.

Altitude

Extended Mode S GPS Altitude Data
Extended Mode S GPS Altitude Data

For each flight we track we display the calibrated altitude reported from the aircraft, which is a pressure-derived value. Extended Mode S data received from some aircraft also includes the GPS-derived altitude of the aircraft. Calibrated Altitude and GPS Altitude values may differ based on the local pressure of the air in which the aircraft is flying. Note that calibrated altitude values reflect the altitude above Mean Sea Level, a constant value used in aviation and other applications. 0 feet/meters above Mean Sea Level does not necessarily reflect an aircraft’s altitude above the ground. GPS altitude values are based on an ellipsoid of the entire earth, but are also not necessarily indicative of altitude above the ground.

Weather

Extended Mode S weather data, including Wind and Outside Air Temperature
Extended Mode S weather data, including Wind and Outside Air Temperature

From an increasing number of aircraft, we are also receiving wind and temperature data. Wind data includes speed and direction from which the wind is blowing. The temperature reported is the temperature of the air outside the aircraft.

Limitations and Future Enhancements

As Extended Mode S data is received directly from the aircraft it is subject to reporting error as there is no checksum sent to verify values received. The most common error in incorrect Mode S data is an unrealistic Mach value. Erroneous values in other data sets are also possible. We are also limited by the number of aircraft broadcasting Extended Mode S data. While the number of aircraft broadcasting full or partial Extended Mode S data is increasing, it is generally limited to aircraft with a newer transponder. Reception of Extended Mode S data also requires that the air navigation service provider where the flight is operating is interrogating the aircraft’s transponder to request the data. While this is increasingly common, it is not yet universal.

On The Radar Logo

Get the latest aviation news delivered to you

Get the latest aviation news delivered to you

Flight tracking and aviation industry news direct to your inbox

Aviation news comes quickly, so join more than 1.7 million others who receive weekly aviation industry and flight tracking news from Flightradar24 direct to their inbox.

Share this article
Latest threads
Latest video

Most wanted airport receiver locations

We’re always looking for additional receiver hosts in areas that either lack coverage or need additional coverage. Help us grow the Flightradar24 ADS-B network.

Trending articles
On The Radar Logo
Get weekly updates on Flightradar24 and have the latest aviation news land in your inbox.
AvTalk Logo

AvTalk Episode 317: The (Q1) results are in

Most wanted airport receiver locations

We’re always looking for additional receiver hosts in areas that either lack coverage or need additional coverage. Help us grow the Flightradar24 ADS-B network.

How flight tracking works

Flightradar24 combines data from several data sources including ADS-B, MLAT and radar data.
Search the blog
Follow us
Latest AvTalk Podcasts
More stories
Anyone who has stood near an airport fence watching aircraft take off and land will likely have noticed the difference in noise levels between…
The Airbus A380 took to the skies for the first on April 27, 2005….
Pakistan has closed its airspace to Indian aircraft. The move comes amid rising tensions following an attack by gunmen in Kashmir and a series…

Flight tracking top 10 aircraft

Explore the top 10 most tracked aircraft and find out why these particular aircraft draw so much interest.

Help to grow our flight tracking coverage

We are continually looking to improve our flight tracking and the airports below are where new receivers will add the most coverage. Apply for a receiver today and if accepted you’ll receiver a free Flightradar24 Business Subscription.

Free ADS-B Receiver
Flightradar24 logo
Try the full Flightradar24 experience free for 7 days
Remove ads and unlock over 50 additional features
On The Radar Logo

Get the Flightradar24 Aviation newsletter

Flight tracking and aviation industry news direct to your inbox

Aviation news comes quickly, so we want to bring more of the aviation world to you with our weekly Flightradar24 aviation newsletter - On The Radar.

On The Radar Logo