Vertical position or vertical location, also known as vertical level or simply level, 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.

Definitions

The

International Organization for Standardization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in A ...

(ISO), more specifically ISO 19111, offers the following two definitions: * ''depth'': "distance of a point from a chosen reference surface measured downward along a line perpendicular to that surface." * ''height'': "distance of a point from a chosen reference surface measured upward along a line perpendicular to that surface"; ISO 6709 (2008 version) makes the following additional definition: * '' altitude'': "height where the chosen reference surface is mean sea level" The International Civil Aviation Organization (ICAO) offers similar definitions: Note: Annex 4 is one of the (currently) 19 annexes to the Chicago Convention on International Civil Aviation
ICAO Doc. 7300
. * '' altitude'': "the vertical distance of a level, a point or an object considered as a point, measured from the mean sea level (MSL);" *''height'': "the vertical distance of a level, a point or an object considered as a point, measured from a specific datum." ICAO further defines: * '' elevation': "the vertical distance of a point or a level, on or affixed to the surface of the earth, measured from mean sea level." I.e., elevation would be the altitude of the ground or a building.

Derived quantities

Several physical quantities may be defined based on the definitions above: * Depth below seafloor * Depth in a well * Drying height * Dynamic height * Ellipsoidal height * Geocentric altitude * Geopotential * Heights in geodesy * Height above mean sea level * Height above average terrain *

Height above ground level In aviation, atmospheric sciences and broadcasting, a height above ground level (AGL or HAGL) is a height measured with respect to the underlying ground surface. This is as opposed to height above mean sea level (AMSL or HAMSL), height above ell ...

Measured depth In the oil industry measured depth (commonly referred to as MD, or just the depth) is the length of the drilled borehole. In conventional vertical wells, this coincides with the true vertical depth, but in directional or horizontal wells, espe ...

* Normal height * Orthometric height * Thickness (geology) *

True vertical depth True vertical depth'is the measurement of a straight line perpendicularly downwards from a horizontal plane. In the petroleum industry, true vertical depth, abbreviated as TVD, is the measurement from the surface to the bottom of the borehole ...

Units

Vertical distance quantities, such as orthometric height, may be expressed in various units: metres, feet, etc. Certain vertical coordinates are not based on length, for example,

geopotential number Geopotential is the potential of the Earth's gravity field. For convenience it is often defined as the ''negative'' of the potential energy per unit mass, so that the gravity vector is obtained as the gradient of this potential, without the negati ...

s have units of m²/s². Normalization by a constant nominal gravity value (units of m/s²) yields units of metre, as in

geopotential height Geopotential height or geopotential altitude is a vertical coordinate referenced to Earth's mean sea level, an adjustment to geometric height (altitude above mean sea level) that accounts for the variation of gravity with latitude and altitude. ...

(based on standard gravity) or dynamic height (based on

normal gravity In geodesy and geophysics, theoretical gravity or normal gravity is an approximation of the true gravity on Earth's surface by means of a mathematical model representing Earth. The most common model of a smoothed Earth is a rotating Earth ellips ...

at 45 degrees latitude). Despite the dimension, the vertical coordinate still does not represent distance, as would be measured with a ruler. Sometimes a standard ''geopotential metre'' (symbol gpm or m') is introduced for emphasis. However, this practice is not acceptable with the International System of Units (SI): the Guide for the Use of the International System of Units, section 7.5 (Unacceptability of mixing information with units), states that ''"When one gives the value of a quantity, any information concerning the quantity or its conditions of measurement must be presented in such a way as not to be associated with the unit."''. Another non-SI unit is the ''vertical metre'', introduced when there may be confusion between vertical, horizontal, or

slant distance In radio electronics, especially radar terminology, slant range or slant distance is the distance along the relative direction between two points. If the two points are at the same level (relative to a specific datum), the slant distance equals t ...

s. It is used for distance climbed during sports such as mountaineering, skiing, hiking, running or

cycling Cycling, also, when on a two-wheeled bicycle, called bicycling or biking, is the use of cycles for transport, recreation, exercise or sport. People engaged in cycling are referred to as "cyclists", "bicyclists", or "bikers". Apart from ...

Nash, Mike, ''Exploring Prince George: A Guide to North Central B. C. Outdoors'', Vancouver: Rocky Mountain Books, 2004, p. 105. In German-speaking countries the abbreviation 'Hm' for ''Höhenmeter'' ("height metre") is used; if it is preceded by a '±' it refers to the cumulative elevation gain.

Measurement

Various instruments and techniques may be used for measuring vertical position: * Altimeter * Bathymetry * Benchmark (surveying) * Depth gauge * Depth sounding * Hypsometer * Topography * Tide gauge * Water level (device)

Phenomena

Many physical phenomena are related to vertical position, as driven by gravity: * Hydraulic head **

Stage (hydrology) In hydrology, stage refers to the water level in a river or stream with respect to a chosen reference height. Stage is important because direct measurements of river discharge are very difficult while water surface elevation measurements are ...

* Isostasy *

Mean sea level There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value ( magnitude and sign) of a given data set. For a data set, the '' ...

** Geoid ** Sea surface height *

Temperature lapse rate The lapse rate is the rate at which an atmospheric variable, normally temperature in Earth's atmosphere, falls with altitude. ''Lapse rate'' arises from the word ''lapse'', in the sense of a gradual fall. In dry air, the adiabatic lapse rate i ...

* Terrain **

Digital terrain model A digital elevation model (DEM) or digital surface model (DSM) is a 3D computer graphics representation of elevation data to represent terrain or overlaying objects, commonly of a planet, moon, or asteroid. A "global DEM" refers to a discret ...

** Topographic prominence * Vertical displacement ** Post-glacial rebound ** Subsidence ** Tectonic uplift *

Vertical pressure variation Vertical pressure variation is the variation in pressure as a function of elevation. Depending on the fluid in question and the context being referred to, it may also vary significantly in dimensions perpendicular to elevation as well, and these var ...

References

External links

*{{Commons category-inline Vertical position,