Quick Facts
- Type
- Altitude Reference
- Also Known As
- MSL
- Used By
- Pilots, ATC
Definition#
MSL stands for Mean Sea Level. It is the average height of the ocean surface, used as the standard reference point for expressing altitudes on aeronautical charts, in METARs, and for altimeter settings.
Why It Matters Operationally#
Airport elevations, airspace floors and ceilings, and instrument approach altitudes are all expressed in MSL. To determine height above the ground (AGL), subtract the terrain elevation from the MSL altitude.
Related Guides#
- Density Altitude Explained
- How to Read a METAR
- How Airplanes Fly — The Complete Aviation Fundamentals Guide