{{short description|Position along a vertical direction above or below a given vertical datum}} {{for|the supply chain concept|Vertical integration}} thumb '''Vertical position''' or '''vertical location''' is a position along a vertical direction (the plumb line direction) above or below a given vertical datum (a reference level surface, such as mean sea 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. A function with domain along the vertical line is called a ''vertical distribution'' or ''vertical profile''.
==Definitions== The International Organization for Standardization (ISO), more specifically ISO 19111, offers the following two definitions:<ref name="ISO6709:2008">{{cite web|title=ISO 6709:2008(en) preview|url=https://www.iso.org/obp/ui/#iso:std:iso:6709:ed-2:v1:en|website=www.iso.org|publisher=ISO|access-date=8 June 2016}}</ref> * ''depth'': "distance of a point from a chosen reference surface measured downward along a line perpendicular to that surface."<ref name=ISO6709:2008/> * ''height'': "distance of a point from a chosen reference surface measured upward along a line perpendicular to that surface";<ref name=ISO6709:2008/> ISO 6709 (2008 version) makes the following additional definition: * ''altitude'': "height where the chosen reference surface is mean sea level"<ref name=ISO6709:2008/>
The International Civil Aviation Organization (ICAO) offers similar definitions:<ref name=annex4>{{Cite web |url=http://dcaa.trafikstyrelsen.dk:8000/icaodocs/Annex%204%20-%20Aeronautical%20Charts/Annex%204%20Aeronautical%20Charts,%20Edition%20no%2011.pdf |archive-url=https://web.archive.org/web/20160917213355/http://dcaa.trafikstyrelsen.dk:8000/icaodocs/Annex%204%20-%20Aeronautical%20Charts/Annex%204%20Aeronautical%20Charts,%20Edition%20no%2011.pdf |url-status=dead |archive-date=2016-09-17 |author=United Nations - International Civil Aviation Organization |title=Annex 4: Aeronautical Charts - Chapter 1 (Definitions, Applicability and Availability) }} Note: Annex 4 is one of the (currently) 19 annexes to the Chicago Convention on International Civil Aviation ([http://www.icao.int/publications/Documents/7300_cons.pdf ICAO Doc. 7300]).</ref> * ''altitude'': "the vertical distance of a level, a point or an object considered as a point, measured from the mean sea level (MSL);"<ref name=annex4/> *''height'': "the vertical distance of a level, a point or an object considered as a point, measured from a specific datum."<ref name=annex4/> 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."<ref name=annex4/> I.e., elevation would be the altitude of an earth-bound feature, such as the ground or a building.
===Derived quantities=== {{Further|Heights in geodesy}}
Several physical quantities may be defined based on the definitions above: {{div col|colwidth=23em}} *Depth below seafloor *Depth in a well *Drying height *Dynamic height *Ellipsoidal height *Geocentric altitude *Geopotential *Height above mean sea level *Height above average terrain *Height above ground level *Measured depth *Normal height *Orthometric height *Thickness (geology) *True vertical depth {{div col end}}
===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 numbers have units of m<sup>2</sup>/s<sup>2</sup>. Normalization by a constant nominal gravity value (units of m/s<sup>2</sup>) yields units of metre, as in geopotential height (based on standard gravity) or dynamic height (based on normal gravity at 45 degrees latitude). Despite the physical dimension and unit of length, the vertical coordinate does not represent distance in physical space, as would be measured with a ruler or tape measure. Sometimes a '''''geopotential metre''''' (symbol gpm or m') or ''dynamic metre'' is introduced for emphasis.<ref>[http://www.seedmech.com/documents_folder/wmo_no_8.pdf World Meteorological Organization - Guide to Meteorological Instruments and Methods of Observation - Preliminary seventh edition - WMO-No. 8 - Secretariat of the World Meteorological Organization – Geneva – Switzerland - 2006]</ref><ref name="Bjerknes1910">{{cite book | last=Bjerknes | first=V. | author-link=V. Bjerknes | title=Dynamic Meteorology and Hydrography: Part [1]-2, [and atlas of plates] | publisher=Carnegie Institution of Washington | series=Carnegie Institution of Washington publication | issue=v. 1 | year=1910 | url=https://books.google.com/books?id=ub5XAAAAYAAJ&pg=PA13 | access-date=2023-10-05 | page=13}}</ref> However, this practice is not acceptable with the International System of Units (SI).{{efn|The Guide for the Use of the International System of Units, section 7.5 (Unacceptability of mixing information with units), states:<ref name="Thompson Taylor 2018">{{cite web | last1=Thompson | first1=Ambler | last2=Taylor | first2=Barry N. | title=Guide for the Use of the International System of Units (SI) | website=NIST | date=2018-11-10 | url=https://www.nist.gov/publications/guide-use-international-system-units-si | access-date=2020-12-09}}</ref><blockquote>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.</blockquote>}}
Another non-SI unit is the ''vertical metre'', introduced when there may be confusion between vertical, horizontal, or slant distances. It is used for distance climbed during sports such as mountaineering, skiing, hiking, running or cycling.<ref>Nash, Mike, ''Exploring Prince George: A Guide to North Central B. C. Outdoors'', Vancouver: Rocky Mountain Books, 2004, p. 105.</ref> 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.
==Determination== Various instruments and techniques may be used for measuring or determining 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) *Isostasy *Mean sea level **Geoid **Sea surface height *Temperature lapse rate *Terrain **Digital terrain model **Topographic prominence *Vertical displacement **Post-glacial rebound **Subsidence **Tectonic uplift *Vertical pressure variation
==See also== {{div col|colwidth=23em}} *Chart datum *{{section link|Geodesy|Heights}} *Geographic coordinates *Horizontal position *Hypsometry *Physical geodesy *Vertical and horizontal *Vertical separation (aviation) *Water level {{div col end}}
==Notes== {{notelist}}
==References== {{reflist}}
==Further reading== * IOGP (2018) ''Geomatics Guidance Note 24: Vertical data in oil and gas applications'', International Association of Oil & Gas Producers (IOGP), Geomatics Committee, Geodesy Subcommittee. Report 373–24, April 2018. [https://www.iogp.org/bookstore/product/geomatics-guidance-note-24-vertical-data-in-oil-and-gas-applications/]
==External links== *{{Commons category-inline}}
Category:Vertical position