A good few years back I used to deal with noise and track complaints from the public, including people who 'knew' what altitudes aircraft were supposed to be flying at and what altitude they reported them flying at in their complaints. I can't recall a single example of the hundreds of complaints that I recorded and analysed where a complainant stated the height that the aircraft was flying at, was correct. The allegation altitude was always way way too low to that actually recorded. The complainants also included previous pilots and other 'experts' makibng all sorts of assumptions from their knowledge or lack of about what they were actually seeing. The easiest comparison I used to make was with witness reports and how they vary to any given event, a good case being the Biggin Hill Biz jet accident, where despite many seeing it, there was not a conclusive set of witness accounts that gave a reliable picture of the event.
I'd also question the data accuracy of the picture above too, particularly how the altitude displayed is matched to QNH and a whole host of data correlation and verification, not least of which is geographical map, to radar overlay of that specific map and recorded track correlation. Getting those correct is a long laborious process, ask anyone who's done it
, and involves a bit more than buying a map from a supplier and sticking it underneath a radar track ...
I used to test myself, watching a typical aircraft B737, guess its height over the airfield and then replay the recording. If I got withing 500ft of the altitude I was very lucky, despite doing this many many times. If I couldn't do it accurately, despite being involved in it as my day job, the chances of a 'lay' person doing it accurately are even more remote.