Originally Posted by
Airbubba
Are you saying jitter or quantization in the received ADS-B data is such that subsequent changes in position may indicate erroneous rates and accelerations unless some form of smoothing or filtering is done?
No, it's much simpler than that.
The data, as received from the aircraft (lat/lon, altitude, track, groundspeed, Vrate), is basically good.
So you can be pretty confident that a plot of, say, altitude or groundspeed vs position will be accurate.
The problem is that the chronological order in which FR24 lists the data doesn't necessarily match the order in which it was transmitted (those thousandth-of-a-second precision timestamps that FR24 shows are nonsense and haven't originated from the aircraft). So, for an aircraft that's on final approach on a constant track, out-of-sync position reports will typically manifest themselves as a spurious 180° change in track, as is apparent in the TK6491 data at 01:16:37 and 01:16:55, for example.
It follows that if one tries to use those unreliable timestamps to derive second-order parameters, it's asking for trouble, as in that absurd "33,000 ft/min" climb rate that several posters have quoted.