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 ):
- In the case of buildings, for example, the building height measured at a level point as the height of the structure , and the ridge height up to the top of the roof , which is referred to in the building regulations . In the case of skyscrapers, for example, which also have high antennas, height records are also measured up to their top tip ( structural height ); see tallest building .
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":
- Height above sea level (m above sea level, m above sea level, m above sea level) in relation to asurvey symbol definedas the zero point . Since the systems of different countries refer to different zero points and even different seas, there is a jump in altitude at the state borders.
- In higher geodesy the orthometric height , the normal-orthometric, dynamic and ellipsoidal height , as well as the normal height . All define themselves in terms of an earth figure and various theories, see height (geodesy) .
- 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 .
Further height references
- In the case of flight altitudes , the height above ground is referred to as AGL ( above ground level , height ), the height above sea level as MSL ( mean sea level , altitude ) and the altitude in relation to the flight level as FL ( flight level )
- In the railway sector, measurements are made on the upper edge of the rail , in road traffic on the middle surface layer upper edge (street level).
- Height is also the abbreviation for angle of elevation (usually in degrees or radians), such as the astronomical height of a star above the mathematical horizon, or the pole height (= geographical latitude).
- Friedrich Kohlrausch : Practical Physics. For use in teaching, research and technology. Volume 1. 24th, revised and expanded edition. Teubner, Stuttgart 1996, ISBN 3-519-23001-1 .
- Karl-Heinrich Grote, Jörg Feldhusen (Ed.): Dubbel. Paperback for mechanical engineering . 21st, revised and expanded edition. Springer, Berlin et al. 2005, ISBN 3-540-22142-5 .