FlightAware Discussions

ADS-B and weather data. How?

Received a email from Radarbox today.

AirNav Systems is pleased to announce the release of a new Raspberry Pi build (software update) for feeders sharing data with RadarBox.com. The new build (v0.4.2) allows for weather data to be collected from the ADS-B data sent by your Raspberry Pi.

The weather data that is collected from your Raspberry Pi ADS-B data includes:

  1. Air Temperature
  2. Wind Speed
  3. Wind Direction

Once collected, the weather data is then processed and used to build and improve the RadarBox Global Weather Model.

I’m surprised how they extract air temperature data from ADS-B data.

If it is clear to me at wind speed that they are using relative ( airspeed indicator) and absolute speed (GPS), then how can the temperature be calculated from the air pressure?

It’s not super accurate.

Total air temperature - Wikipedia

It’s done in tar1090, my readsb does it as well.

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The Radarcape devices are showing this in their data as well.
I was always curious how they do that.

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Comm-B data will report true airspeed and Mach number. From this you know the speed of sound in the surrounding air. Speed of sound in air depends (mostly) only on air temperature. You’re kinda working backwards from the outputs of the air data computer back to its inputs.

As wiedehopf says it’s not very accurate, the transmitted data is heavily quantized which turns into large steps in possible temperature values.

There is also a meteorological report Comm-B message type (MRAR), but dump1090-fa doesn’t know how to decode that and I’m yet to see it in the wild (though apparently there’s at least one interrogator in Europe somewhere that asks for it)

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I’d like to qualify that, it’s especially inaccurate below mach 0.4, with mach increasing it becomes quite a bit more accurate.

Actually looked for that once and it was only a handful of transponders that were answering those interrogations.
I believe it was CRJs which are very rare in Europe.

Aircrafts are used to refine weather forecasts, with programs like AMDAR. Interestingly, MODE-S was not really used before the pandemic and the loss of aircraft-based observations but there is work in progress. The second link shows it’s a little more complicated than just getting the data. Many corrections need to be applied.

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