[eli5] How does an altimeter work? How does it know how high you are off the ground?

Question

[eli5] How does an altimeter work? How does it know how high you are off the ground?

In: 69

Answer 1

Pretty much correct explanations so far, but missing a crucial detail.

When you are approaching a airport for landing, you tune in to the airport’s information broadcast. This includes local wind, traffic pattern and the current local barometric altimeter setting.

This info is updated periodically, and each update is given a sequential alphabetic name, e.g. Alpha, Bravo, Charlie, Delta, Foxtrot,…

So when you call the airport, you announce where you are, and that you have heard, e.g. “Bravo” information.