Definition
A standard reference level corresponding to the average height of the ocean's surface, used as the zero point for measuring altitude and atmospheric pressure in aviation. The reference is defined as Mean Sea Level (MSL) to account for tides and wave action.
Plain English
The average height of the ocean, used as the zero mark from which altitudes and pressures are measured in flying.
Context Anchor
Seen in airport elevation, aircraft altitude, weather, and performance discussions.
Why Pilots Care
Sea level provides the standard reference for atmospheric pressure and temperature, which directly affects aircraft performance calculations and altimeter readings.
Analogy
Sea level works like the zero mark on a ruler. Once everyone uses the same zero point, height measurements can be compared clearly.
Intuition Check
Sea level does not mean the exact height of waves or tides at a beach today. In aviation, it means an average ocean-surface reference used for measuring height.
Example Sentence 1
Example Sentence 2
Standard atmosphere tables list temperature and pressure values at sea level as 15 degrees Celsius and 29.92 inches of mercury.