Here's one that may seem silly: to what height, precisely, is an
altimeter calibrated to?

The bottom of the landing gear? The height of the static port? the chord
line of the fuselage? In a Cessna, the difference between these is
minimal, but on an airliner, you're talking about a possible +/- 10-15
feet (even discounting the radar altimeter).

What is the answer, o Swammi of Salami?

TheSmokingGnu