geography Geography (from Greek: , ''geographia''. Combination of Greek words ‘Geo’ (The Earth) and ‘Graphien’ (to describe), literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, a ...

, the

centroid In mathematics and physics, the centroid, also known as geometric center or center of figure, of a plane figure or solid figure is the arithmetic mean position of all the points in the surface of the figure. The same definition extends to any ...

of the two-dimensional shape of a region of the Earth's surface (projected radially to sea level or onto a

geoid The geoid () is the shape that the ocean surface would take under the influence of the gravity of Earth, including gravitational attraction and Earth's rotation, if other influences such as winds and tides were absent. This surface is exten ...

surface) is known as its geographic centre or geographical centre or (less commonly) gravitational centre. Informally, determining the centroid is often described as finding the point upon which the shape (cut from a uniform plane) would balance. This method is also sometimes described as the "gravitational method". One example of a refined approach using an azimuthal equidistant projection, also potentially incorporating an iterative process, was described by Peter A. Rogerson in 2015. The abstract says "the new method minimizes the sum of squared great circle distances from all points in the region to the center". However, as that property is also true of a centroid (of area), this aspect is effectively just different terminology for determining the centroid. In 2019, New Zealand's GNS Science also used an iterative approach (and a variety of different projections) when determining a centre position for New Zealand's Extended Continental Shelf. However, other methods have also been proposed or used to determine the centres of various countries and regions. These include: * centroid of volume (incorporating elevations into calculations), instead of the more usual centroid of area as described above. * centre point of a bounding box completely enclosing the area. While relatively easy to determine, a centre point calculated using this method will generally also vary (relative to the shape of the landmass or region) depending on the orientation of the bounding box to the area under consideration. In this sense it is not a robust method. * finding the longitude that divides the region into two equal area parts to the east and west, and then similarly the latitude that divides the region into two equal area parts to the north and south. Like the bounding box approach described above this method would not generally locate precisely the same point if the same shaped region was oriented differently. As noted in a

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

document, "There is no generally accepted definition of geographic center, and no completely satisfactory method for determining it." In general, there is room for debate around various details such as whether or not to include islands and similarly, large bodies of water, how best to handle the curvature of the Earth (a more significant factor with larger regions) and closely related to that issue, which

map projection In cartography, map projection is the term used to describe a broad set of transformations employed to represent the two-dimensional curved surface of a globe on a plane. In a map projection, coordinates, often expressed as latitude and longit ...

to use.

Notable geographical centres

* Geographical centre of Earth * Axis mundi * Omphalos of Delphi

Geographic centres in Africa

Geographic Centre of Uganda (Amolatar Monument) The geographic centre of Uganda is north of Lake Kyoga in Olyaka village, Olyaka parish in Namasale sub-county in Amolatar District, Northern Uganda. The point is marked by the Amolatar Monument which displays the names of all ethnic tribes ...

Geographic centres in Asia

* Geographical midpoints of Asia, in China or

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eigh ...

* Geographical centre of India ** Zero Mile Stone (Nagpur) * Geographic center of Iran * Geographic centre of Sri Lanka * Geographical centre of the Korean Peninsula * Geographical centre of the Philippines * Geographical centre of the Russian Federation * Geographical centre of the Soviet Union * Geographic center of Taiwan

Geographic centres in Europe

Geographical centre of Switzerland The geographical centre of Switzerland has the coordinates (Swiss Grid: 660158/183641). It is located at Älggi-Alp in the municipality of Sachseln, Obwalden. The point is the centre of mass determined in 1988 by Swisstopo. As the point is dif ...

Centre points of the United Kingdom There has long been debate over the exact location of the geographical centre of the United Kingdom, and its constituent countries, due to the complexity and method of the calculation, such as whether to include offshore islands, and the fact tha ...

** Geographical centre of Great Britain ** Centre points of counties of the United Kingdom ** Geographic centre of England ** Geographical centre of Scotland ** Geographic centre of Wales

Geographic centres in North America

* Geographic center of North America * Geographic centre of Canada * Geographic center of the United States ** List of geographic centers of the United States

Geographic centres in Oceania

* Centre points of Australia * Geographic centre of New Zealand

Geographic centres in South America

* Geographical Center of South America * Geographical Center of Colombia

References

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