1-Is the flightaware reported altitude relative to Mean Sea Level (MSL) or Hight Above Ellipsoid (HAE)?
2-Is the flightaware reported altitude barometric (altimeter based) or geometric (GPS based)?
3-What altitude is reported by flightaware when the aircraft is sitting on the runway? Does this value take into account the height of the cockpit? Does this value take into account the height of the runway itself? (I know that the aircraft usually disables its adsb transmitted before landing; this question applies where the transmitter remains on.)
For example: What altitude is reported when a 747 is taxiing on a runway that’s is elevated 500 feet?