Location (geography)

The location in the geographical sense is your position on the earth's surface or in a suitable geometrical reference system. Semantically equivalent are also terms such as position, your position or Topozentrum (from Greek topos for location ) to which other terms of various scientific disciplines come. The determination of the location is often referred to as a location or a position.

The site is not only important for its own orientation, but is also in measurements of the (local) zero point of the so-called topocentric coordinate system. In a broader sense - as in astronomy or space - the location can also be on other celestial bodies.

Overview

The specification of a site can be done in very different ways, for example,

  • By geographical coordinates or using GPS waypoints certain
  • Relative to another point - about 50 meters south of the town hall or west of the summit XY at about 2300 meters above sea level,
  • In a local coordinate system - defined by the reference point and orientation,
  • By distances or kilometer - about the river kilometer 123.4,
  • By specifying an intersection or by street and house number.

Location in observations and measurements

The value of an observation or measurement on an outdoor location usually also depends on the reliability of the location information. For observations in the wild usually a local indication to approximately 100 m is reasonable, as it is easily possible with map.

With higher demands - eg for geological recordings or antenna locations - can be clearly laid out in the map distances, directions to landmarks gepeilt or kartometrische measurements are made. In geodesy, the instrument point of the theodolite is determined by angle and distance measurements to survey points in navigating current price determination ( coupling ). Carried beacon or GPS Suitable adjuvants can also be magnetic measurements, satellite imagery or photogrammetry.

Exact positions are usually given in a coordinate system that is related to a defined reference point or zero point. The most important of these systems rely on elaborate measurements but are thus an absolute, permanent frame of reference.

Absolute location information

In this sense, the following coordinate systems can be regarded as absolute:

  • Geographic coordinates ( latitude and longitude), based on the reference ellipsoid of land surveying or (simply ) a mean globe. You can place a number of requirements are derived or taken from a map, mostly as latitude and longitude; but requires a
  • Complete location information and a height;
  • Relate in the geosciences at the Earth's center,
  • In astronomy and space on the barycenter of the solar system.

Relative location information

In everyday life and at unprepared dispensed location messages but relative location information are usually more important. Often they are

  • Related to a road, or an object, Address ( house number, object)
  • A distance from an intersection
  • Direction and distance of a striking building
  • Kilometer ( km stone, river kilometer )
  • Distance of a striking object

Conversion of relative positions

Important for urgent local information (accident or imminent danger ) is primarily the uniqueness of one's own location message, but also the accessibility of the transport network. For the evaluation of less urgent information, such as measurements, most relative location information can be converted into absolute, about

  • Means of a map or a city map,
  • With Google Earth,
  • From the land or a building plan.

For the accuracy of location information

While reports of incidents or accidents, the uniqueness of the location information has great importance when measuring the accuracy of the position information must correspond approximately to the measurement accuracy. For retrieval of a point the necessary accuracy also depends on the task.

Some examples from astronomy and technology may illustrate this

  • Astronomical angle measurements to ± 1 "→ placement on at least ± 30 m (corresponding to 1 " at the geocenter ).
  • A bright meteor ( fireball ), direction to 5 ° is detected ( in the constellation XY) → placement on at least 5 km ( a verglühender Meteor is 50-100 km).
  • Terrestrial goals depending on the distance: measuring accuracy (in degrees) x Distance / 57.3 something like this: an event in 10 km, direction estimated to be 10 ° → 1.7 km (1 km Location enough ).

Literature and links

  • Heribert Kahmen: Surveying, 19th edition, published by De Gruyter.
  • Axel Bark: Sailing license, 9th edition, Bielefeld 1982.
  • Brockhaus (6- bändig ), Wiesbaden 1959-61.
  • Terms of the Astronomical, Physical and Mathematical Geodesy ( PDF; 1019 kB)
  • Spherical astronomy and location
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