Can you please check were I stated that I
have been involved in ADS-B development
or that these were
original ADS-B transmissions
or that I inferred that the messages were
transmitted by an aircraft in that form
as you yourself quoted, I said
I am assuming that the raw data presented reflects directly what was received by the ADS-b ground station
ATC systems receive ADS-b data from ground stations over data links. The links transfer data packages that contain combined squitters of ADS-b transmissions.
The data package formats were ADS-b receiver manufacturer specific but content wise were remarkably similar to those displayed, however they did have validity flags.
I am fully aware that FR24 relies on
enthusiast Mode S receivers but am amazed that you seem to consider that this particular programmer was astute enough to be able to write a program that selected just these two particular messages to drop the altitude (while keeping the lat/long from the same squitter) when all his other messages were presented in totality.