Originally Posted by
ManaAdaSystem
So what is the difference between downloaded data and RL data? I would imagine the RL data is the downloaded data, but at a later stage.
I think you've answered that question yourself:
Originally Posted by
ManaAdaSystem
Weird data from FR24? I have seen this many times, even near major airports. I have seen aircraft flying below safe altitude right into mountains. Never happened. I have seen aircraft hanging in the air, then plunge down to the runway. Never happened. I have seen aircraft overshooting runways by miles.. Never happened. Aircraft backing in the air. Never happened. Aircraft suddenly gone. Never happened.
I've seen the same at times on the (few) occasions that I've needed to use FR24 in realtime (something I normally try to avoid). I've never seen any such issues to date in downloaded data. If you want to know the reason for the difference, go ask FR24 (I'll be interested in the answer, too and, no, I don't work for them!).
Now you are saying FR24 data can’t be relied on, but you also produce graphs based on this data?
No, I'm saying that typical issues with the data, which I've already acknowledged on a number of occasions (out-of-sequence messages, wrongly combined position/velocity data, unadjusted altitudes, etc) can usually be mitigated so that you end up with something that turns out to be pretty close to the relevant bits of the FDR trace once that's published. The only FR24 issues I've come across that can't be mitigated are where aircraft don't have GPS, or those that don't have ADS-B at all, where FR24 attempts to use crowd-sourced multilateration, with dire results (which may be what our northern friend is describing).