Originally Posted by
DaveReidUK
Interesting graphic.
The altitude spike where the aircraft dips below the runway surface(!) accompanied by a single, instantaneous 2000+ fpm ROC value is clearly an artifact (unless Newton got it all wrong), probably coinciding with rotation.
There is a similar, spurious altitude spike towards the RH edge of the plot, which you have wisely ignored - that one is easier to account for because a distance-vs-time plot shows the aircraft flying backwards at that point (i.e. it's a timestamp anomaly rather than bad ADS-B data).
In addition to often mentioned lack of fidelity in the ads-b info available on the internet. It is normal to see a VSI indication dip slightly at rotation. well, it used to be, not familiar with the most recent 15 years of aircraft development.