Originally Posted by
Flagon
LIS - are the source/time/date of your 'reports' officially substantiated? Remember they are Mode C readings as well. Someone previously here cast doubt on the track displayed too. Whether that post still exists........? What explanation did your 'source' have for '353'?
There is a tendency to take what was displayed to the controller or brought up on a replay screen as 'the information from the aircraft'. It may have had significant massaging before it appears on the screen. For example ADS-B and SSR are always going to be out of step and your system is receiving both so to avoid the position report jumping back and forth the information from the aircraft SSR transponder and the ADS-B downlink are processed by a 'multi-sensor tracker' of some sort and converted into a 'Track' for the aircraft.
The reports state that the controllers were receiving ADS-B reports from the aircraft. If that is the case then they would be receiving those positions a lot more frequently than the Track update on the controller display. Each of the ADS-B reports gives detail on the GNSS position, the time the position was valid, the altitude of the aircraft, the vector state of the aircraft, etc etc, (See RTCA DO-260B). This information will have been stored in the ATC systems. At best there will be a half second trail of this information, that would allow a very detailed trajectory (track, airspeed, ground speed and altitude profile - possibly with GPS altitude as well) to be created relatively simply.
I do not understand why this has not been done it would not see the aircraft all the way to the surface but it
would answer many questions and remove some of the wilder speculations.