AMSL is an acronym for "above mean sea level," a measurement commonly used in aviation, cartography, and meteorology to define the vertical distance or altitude of an object or location relative to the average sea level. Mean sea level involves the calculation of a midpoint between high and low tide levels over an extended period, ensuring a reliable reference point for elevation measurements.
AMSL indicates the altitude of an aircraft, terrain, or any other point on the Earth's surface above the average sea level, thereby serving as a reference point for determining height variations. Meteorological measurements, such as atmospheric pressure, temperature, and wind speeds, may also be expressed with reference to AMSL. Terrain features, buildings, or peaks are likewise measured using AMSL to provide an accurate understanding of their altitude or elevation.
This term is commonly used in aviation to ensure proper flight safety by allowing pilots to determine their height above the ground or the altitude they should maintain. It is essential for navigation, ensuring aircraft can maintain safe separation from the terrain and obstacles, and for adherence to minimum altitude requirements during takeoff, approach, or landing.
AMSL provides a standardized reference system globally, enabling precise comparison and exchange of elevation measurements and ensuring accurate communication between different actors in aeronautical operations, geographic information systems, or meteorological research.
