such as towns, mountains and other landmarks.

Geographic locations

The top of and other structures.

buildings

infrastructure, particularly underground.

Mining

Flying objects such as or helicopters below a Transition Altitude defined by local regulations.[2]

airplanes

Elevation or altitude above sea level is a standard measurement for:

AMSL – above mean sea level

[3]

ASL – above sea level

[4]

FAMSL – feet above mean sea level

[5]

FASL – feet above sea level

[6]

MAMSL – metres above mean sea level

[5]

MASL – metres above sea level[6]

[5]

MSL – mean sea level

[7]

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 in English are:


For elevations or altitudes, often just the abbreviation MSL is used, e.g., Mount Everest (8849 m MSL), or the reference to sea level is omitted completely, e.g., Mount Everest (8849 m).[7]

especially levelling.

Surveying

(such as 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.

Global Navigation Satellite System

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.

Pressure altimeter

in aerial photography.

Stereoscopy

Aerial and satellite laser altimetry.

lidar

Aerial or satellite .

radar altimetry

Altimetry is the measurement of altitude or elevation above sea level. Common techniques are:[8][9]


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.[10]

Depth below seafloor

Height above average terrain

Height above ground level

List of places on land with elevations below sea level