Height above mean sea level

Height above mean sea level is a measure of the vertical distance (height, elevation or altitude) of a location in reference to a historic mean sea level taken as a vertical datum. In geodesy, it is formalized as orthometric heights. The quantity is called "metres above mean sea level" in the metric system, while in United States customary and imperial units it would be called "feet above mean sea level". Mean sea levels are affected by climate change and other factors and change over time. For this and other reasons, recorded measurements of elevation above sea level at a reference time in history might differ from the actual elevation of a given location over sea level at a given moment. Metres above sea level is internationally the standard measurement of the elevation or altitude of: Geographic locations such as towns, mountains and other landmarks. The top of buildings and other structures. Flying objects such as airplanes or helicopters in China and below Transition Altitude (or TA) in Russia and many CIS member countries. The elevation or altitude in metres above sea level of a location, object, or point can be determined in a number of ways. The most common include: 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, that measures atmospheric pressure, which decreases as altitude increases. As atmospheric pressure changes 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 lowering of mean sea level.

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related publications (18)

Related units (3)

Related concepts (16)

Related lectures (13)

Wintertime vertical distribution of air pollution in suburban Fairbanks during the ALPACA 2022 field campaign

Julia Schmale, Andrea Baccarini, Roman Pohorsky

The Alaskan Layered Pollution and Chemical Analysis (ALPACA) field campaign investigated the sources and processing of wintertime urban pollution in Fairbanks, Alaska in January and February 2022. Several sites located around the city of Fairbanks collecte ...

2023

, , ,

The use of radar for precipitation measurement in mountainous regions is complicated by many factors, especially beam shielding by terrain features, which, for example, reduces the visibility of the shallow precipitation systems during the cold season. Whe ...

2020

Static behavior of reinforced UHPFRC beams with minimal cover thickness

Eugen Brühwiler, Bartlomiej Wojciech Sawicki

Because of its high tensile strength and deformation capacity, UHPFRC (Ultra High Performance Fiber Reinforced Cementitious composite) can theoretically be used without any reinforcement bars or prestressing. However, for more economical design and for rea ...

2019

Height

Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For example, "The height of that building is 50 m" or "The height of an airplane in-flight is about 10,000 m". For example, "Christopher Columbus is 5 foot 2 inches in vertical height." When the term is used to describe vertical position (of, e.g., an airplane) from sea level, height is more often called altitude. Furthermore, if the point is attached to the Earth (e.

Radar altimeter

A radar altimeter (RA), also called a radio altimeter (RALT), electronic altimeter, reflection altimeter, or low-range radio altimeter (LRRA), measures altitude above the terrain presently beneath an aircraft or spacecraft by timing how long it takes a beam of radio waves to travel to ground, reflect, and return to the craft. This type of altimeter provides the distance between the antenna and the ground directly below it, in contrast to a barometric altimeter which provides the distance above a defined vertical datum, usually mean sea level.

Vertical position

Vertical position or vertical location is a position along a vertical direction above or below a given vertical datum (reference level). Vertical distance or vertical separation is the distance between two vertical positions. Many vertical coordinates exist for expressing vertical position: depth, height, altitude, elevation, etc. Points lying on an equigeopotential surface are said to be on the same vertical level, as in a water level.

Explores altitudes definitions, measurement principles, and geomatics elements for accurate height determination using leveling instruments.

Covers the concept of densifying the altimetric network by measuring height differences and establishing paths between points.

Discusses geoid elevation, orthometric altitude, altitudes, Swiss local geoid, and altitude systems.