Originally Posted by
ATC Watcher
I am not sure any of the 2 aircraft involved were equipped with ADS-B out , more likely the data you are talking about comes from F24 , and the data then coms from the transponders relayed via a few private antennas on the ground. It is not the certified ADS-B we talk about in ATC or Commerciall aviation.
As to using the vertical rates mentioined earlier , I persoally doubt the calculations and the figures posted . , FR24 is a great tool but is not exact science
The posts above pretty clearly say it is ADS-B data. And if the aircraft were not ADS-B equipped, flying where they were would be illegal -- under/within Class B airspace.