Metres above sea level
Metres above mean sea level (MAMSL), or simply metres above sea level (MASL or m.a.s.l.), is a standard metric measurement in metres of the elevation of a location in reference to historic mean sea level; the determination of what actually constitutes mean sea level over time however, may be determined by other parameters, such as the effects of climate history and climate change, and may have differed in the past, as well as in the future, from that established by historic, modern, documented elevations.
Metres above sea level is the standard measurement of the elevation or altitude of:
- a geographic location such as a town, mountain, or other landmark
- the elevation of the top of a building or other structure
- or the altitude of an airplane or other flying object.
The elevation or altitude in metres above sea level of any location, object, or point, can be determined in a number of ways. The most common include:
- Global Positioning System (GPS) which triangulates its location in reference to multiple satellites
- an altimeter, which typically measures atmospheric pressure, which decreases as altitude increases.
- a topographic map or digital elevation model map, for which elevations have been determined by aerial photography or surveying.
Accurate measurement of historical mean sea level is complex. Land mass subsidence (as occurs naturally in some islands) can give the appearance of rising sea levels over time. Conversely, markings on land masses that are uplifted due to geological processes can suggest a lowering of mean sea level.
Other measurement systems
Feet above sea level is the most common analogue for metres above sea level in the American measurement system.
- Ricardo Bressani, Ricardo; Carlos Chon (1996). "Effects of altitude above sea level on the cooking time and nutritional value of common beans" (PDF). Plant Foods for Human Nutrition (Formerly Qualitas Plantarum) 49 (1): 53–61. doi:10.1007/BF01092522. Retrieved 2007-05-06.
- "Meters above Sea Level - What does MSL stand for? Acronyms and abbreviations by The Free Online Dictionary.". Retrieved 2007-05-06.