# height

Height describes the distance between an object point and a reference line or surface. It is a one-dimensional quantity and one of the three spatial dimensions that are specified in units of length (usually in meters).

For all physical objects on earth, the height is the perpendicular distance from a reference surface , i.e. it assumes the natural (possibly mathematically defined) perpendicular direction . This applies in a broader sense to all bodies in a gravitational field , which provides a reference system for above-below . The height networks of the official land surveying systems are defined with regard to such a reference area as geoid (mean sea level) or quasigeoid .

## Height of an object

In general, the geometric height is the greatest distance from a base line (as in the case of a flat triangle ) or a base area , i.e. the maximum of all normal distances between all points. The value is then called the total height of the object. If this applies to a point, this is the tip of the object.

• An example is the dimensions of an object in logistics, as in common parlance

In technical applications, the earth's surface can also be used as a reference ( height above ground ):

## Altitude

The altitude of places is shown on (two-dimensional) maps i. d. Usually represented by contour lines . In Geodesy to use different height systems for the altitude to which different level definitions and reference areas are based. For the indication of terrain altitudes (engl. Elevation ), these reference surfaces are generally on the at one level measured average sea level moored.

The geosciences therefore differentiate between absolute height and relative height :

• the absolute height is the "height above zero":
• the relative height ( terrain height ) is the height above ground , the physical height by which a geographical object towers above the surroundings

The "highest mountain on earth" is an example of the difference:

• Mount Everest (Tschomolungma) in the usual sense, which is measured in absolute, orthometric height at 8,848 meters above sea level,
• but at a relative height to the foot of the mountain on the deep sea bed, this is the Mauna Kea volcano , a peak of the massif that forms the island of Hawaii .
• In addition, there are other measurement bases for the height (to the center of the earth as absolute height in relation to an earth idealized as a sphere) or notch height ; see Highest Mountain .

## Height measurement

The height can be measured by leveling (horizontal sighting), tachymetry (measuring vertical angles), GPS or barometric . Special devices for measuring heights are called altimeters .