##### Mean Sea Level (MSL) Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which [[atmospheric pressure]] is measured to calibrate [[altitude]] and, consequently, aircraft flight levels. The term above sea level (ASL) generally refers to above mean sea level (AMSL). The term APSL means above present sea level, comparing sea levels in the past with the level today. >Covered in: >Mentioned in: >References: [[WP Sea Level|🌍]] >Required by: > >Related to: