Vertical position

thumb|upright=1.5|Map of the undulation of the geoid in meters (based on the EGM96 gravity model and the [[WGS84 reference ellipsoid).]]

elevation of a location in reference to a historic mean sea level taken as a vertical datum

thumb|Altitude is a vertical measurement between a reference datum and an object. Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometry, geographical survey, sport, or atmospheric pressure). Although the term altitude is commonly used to mean the height above sea level of a location, in geography the term elevation is often preferred for this usage.

optical instrument used to establish or check points in the same horizontal plane

thumb|upright=1.4|Vertical distance comparison

thumb|300px|Subsided house, called The Crooked House, the result of 19th-century mining subsidence in [[Staffordshire, England]] thumb|A625 road#Mam Tor road|Mam Tor road destroyed by subsidence and shear, near Castleton, [[Derbyshire]]

point with known height used in surveying when levelling

thumbnail|A wooden tripod holding an optical level is set up firmly on the ground.

thumb|Boiling Point Apparatus or Hypsometer. Image from "Maps and survey" (1913) by Hinks, Arthur R.

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distance over which a quantity decreases by a factor of e; for a planetary atmosphere, the distance over which pressure drops by that factor

elevation of the free surface of a stream, lake or reservoir relative to a specified vertical datum

gauge that indicates the depth underwater, primarily used by divers and on submarines

The maximum water level of a bank or shore

method of measuring the depth of a body of water

measurement of the initial static stability of a floating body

altitude above geoid or mean sea level

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device used for matching elevations

Measurement of height that adjusts for the variation of gravity with latitude and altitude

atmospheric equation in meteorology

A bathometer (also bathymeter) is an instrument for measuring water depth. It was previously used mainly in oceanographical studies, but is rarely employed nowadays. The term originates from Greek βαθύς (bathys), "deep" and μέτρον (métron), "measure".

shape of the ocean surface relative to the geoid

altitude above quasigeoid or mean sea level

organisms capable of living at high altitudes

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