Height above mean sea level: Difference between revisions
→Units and abbreviations: Are these common? I've never seen these abreviations on hilltops, on maps, nor surveying publications. Combining the abbreviation of the unit and the quantity seems plain wrong to me, and surely not approved by SI. Tags: Mobile edit Mobile web edit Advanced mobile edit |
→Units and abbreviations: add citation names "fcc_dot_gov" and "faa_dot_gov" |
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== Units and abbreviations == |
== Units and abbreviations == |
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Elevation or altitude is generally expressed as "[[metre]]s above mean sea level" in the [[metric system]], or "[[Foot (length)|feet]] above mean sea level" in [[United States customary units|United States customary]] and [[imperial units]]. Common abbreviations are: |
Elevation or altitude is generally expressed as "[[metre]]s above mean sea level" in the [[metric system]], or "[[Foot (length)|feet]] above mean sea level" in [[United States customary units|United States customary]] and [[imperial units]]. Common abbreviations are: |
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* AMSL – above mean sea level<ref name=faa-dot-gov>{{Cite report|url=https://www.faa.gov/air_traffic/publications/atpubs/aim_html/appendix_3.html|publisher=United States Department of Transportation, Federal Aviation Administration|archive-url=https://web.archive.org/web/20231101134357/https://www.faa.gov/air_traffic/publications/atpubs/aim_html/appendix_3.html|archive-date=2023-11-01|url-status=live|access-date=2024-01-01|date=2023-10-05|title=Aeronautical Information Manual}}</ref><ref name=fcc_dot_gov>{{Cite report|url=https://wireless2.fcc.gov/helpfiles/AsrHelp/help-towairdetermination.html|publisher=Federal Communications Commission|title=TOWAIR Determination|archive-url=https://web.archive.org/web/20030829002648/http://wireless2.fcc.gov:80/helpfiles/AsrHelp/help-towairdetermination.html|archive-date=2003-08-29|url-status=live|access-date=2024-02-01|quote="Site Elevation (AMSL) - The elevation of the site above mean sea level (AMSL). Height is displayed in meters."}}</ref> |
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* AMSL – above mean sea level{{citation needed|date=October 2021}} |
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* FAMSL – feet above mean sea level{{citation needed|date=January 2024}} |
* FAMSL – feet above mean sea level{{citation needed|date=January 2024}} |
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* FASL – feet above sea level{{citation needed|date=January 2024}} |
* FASL – feet above sea level{{citation needed|date=January 2024}} |
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Revision as of 01:37, 2 February 2024
 | This article needs additional citations for verification. (January 2024) |
Height above mean sea level is a measure of a location's vertical distance (height, elevation or altitude) in reference to a vertical datum based on a historic mean sea level. In geodesy, it is formalized as orthometric height. The zero level varies in different countries due to different reference points and historic measurement periods. Climate change and other forces can cause sea levels and elevations to vary over time.[1]
Uses
Elevation or altitude above sea level is a standard measurement for:
- Geographic locations such as towns, mountains and other landmarks.
- The top of buildings and other structures.
- Flying objects such as airplanes or helicopters below a Transition Altitude defined by local regulations.[2]
Units and abbreviations
Elevation or altitude is generally expressed as "metres above mean sea level" in the metric system, or "feet above mean sea level" in United States customary and imperial units. Common abbreviations are:
- AMSL – above mean sea level[3][4]
- FAMSL – feet above mean sea level[citation needed]
- FASL – feet above sea level[citation needed]
- MAMSL – metres above mean sea level[citation needed]
- MASL – metres above sea level[citation needed]
- MSL – mean sea level
For elevations or altitudes, often just the abbreviation MSL is used, e.g., Mount Everest (8848 m MSL), or the reference to sea level is omitted completely, e.g., Mount Everest (8848 m).[5]
Methods of measurement
Elevation or altitude above sea level is most commonly measured by:
- Global Navigation Satellite System (like GPS), where a receiver determines a location from pseudoranges to multiple satellites. A geoid is needed to convert the 3D position to sea-level elevation.
- Altimeter measuring atmospheric pressure, which decreases as altitude increases. Since atmospheric pressure varies with the weather, too, a recent local measure of the pressure at a known altitude is needed to calibrate the altimeter.
- Stereoscopy in aerial photography.
- Aerial lidar and satellite laser altimetry.
- Aerial or satellite radar altimetry.
- Surveying, especially levelling.
Accurate measurement of historical mean sea levels is complex. Land mass subsidence (as occurs naturally in some regions) can give the appearance of rising sea levels. Conversely, markings on land masses that are uplifted (due to geological processes) can suggest a relative lowering of mean sea level.
See also
- Depth below seafloor
- Height above average terrain
- Height above ground level
- List of places on land with elevations below sea level
References
- ^ "Sea Level: Frequently Asked Questions and Answers" Liverpool, UK: National Oceanography Centre. Retrieved 31 January 2024.
- ^ "Altitude, Flight Level and Height". SKYbrary Aviation Safety. Retrieved 31 January 2024.
- ^ Aeronautical Information Manual (Report). United States Department of Transportation, Federal Aviation Administration. 2023-10-05. Archived from the original on 2023-11-01. Retrieved 2024-01-01.
- ^ TOWAIR Determination (Report). Federal Communications Commission. Archived from the original on 2003-08-29. Retrieved 2024-02-01.
Site Elevation (AMSL) - The elevation of the site above mean sea level (AMSL). Height is displayed in meters.
- ^ Moore, G.W.K.; Semple, J.L.; Hoyland, G. (2011). "Global Warming, El Niño, and High-Impact Storms at Extreme Altitude: Historical Trends and Consequences for Mountaineers". Journal of Applied Meteorology and Climatology. 50 (11): 2197–2209. JSTOR 26175013.
