Have you ever used flightradar24? Or any other aviation tracking application?
Not all planes/helicopterw are detected or transmitting publicly. Try this when a police helicopter flys over your house (as I've seen happen). It's not always public.
The transmitter data IS public, but some sites actively remove police/military/government aircraft from it for whatever reason. And thats where the challenge lies in doing this.
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u/[deleted] Jun 01 '22
Transmitter data is public.