The measure of height with respect to a point on the earth’s surface above mean sea level. Sometimes referred to as station elevation.
Mean Sea Level
The average height of the sea surface water level. For the United States, it is computed by averaging the levels of all tide stages over a nineteen year period, determined from hourly height readings measured from a fix, predetermined reference level. It is used as a basis for determining elevations, as the reference for all altitudes in upper air measurements, and as the level above which altitude is measured by a pressure altimeter for aviation. Often referred to as MSL.
The vertical distance above mean sea level that is the reference level for all current measurements of atmospheric pressure at that station.