Cassandra, working on her Sport Pilot ticket on the Florida coast, writes: I’ve just started my flight training, and have learned about the two different ways that altitude is expressed: AGL and MSL. Above Ground Level is self-explanatory, but I’m having a harder time wrapping my head around Mean Sea Level. I mean, I get that it’s the altitude above sea level, but what’s the “mean” all about?
Source: general aviationQuestions from the Cockpit: What’s so mean about mean sea level?