Geographical centre of Earth
The geographical centre of Earth is the geometric centre of all land surfaces on Earth. Geometrically defined it is the centroid of all land surfaces within the two dimensions of the Geoid surface which approximates the Earth's outer shape. The term centre of minimum distance specifies the concept more precisely as the domain is the sphere surface without boundary and not the sphere as three-dimensional body. Explained in a different way, it is the location on the surface of Earth where the sum of distances to all locations on land is the smallest. If you had an airplane with an infinite energy resource and fly from one start location on Earth to one location on a land surface somewhere on Earth and back again and repeat that from the same start location to all possible destination locations, the starting locations where the total travel distance sums up as the smallest, marks the geographical centre of Earth. Its distance definition follows the shortest path on the surface of Earth along the great circle (orthodrome). History of the concept 

Around the world throughout history many real and illusive places were identified as axis mundi or centers of the world. In 1864, Charles Piazzi Smyth, Astronomer Royal for Scotland, gave in his book Our Inheritance in the Great Pyramid the coordinates with , the location of the Great Pyramid of Giza in Egypt. He stated that this had been calculated by "carefully summing up all the dry land habitable by man all the wide world over". In October of that year, Smyth proposed to position the prime meridian at the longitude of the Great Pyramid because there it would "pass over more land than [at] any other [location]". He also argued the cultural significance of the location and its vicinity to Jerusalem. The expert committee deciding the issue, however, voted for Greenwich because "so many ships used the port of London". In 1973, Andrew J. Woods, a physicist with Gulf Energy and Environmental Systems in San Diego, California, used a digital global map and calculated the coordinates on a mainframe system as , in modern-day Turkey, near the district of Kırşehir, Seyfe Village approx. 1,800 km north of Giza. In 2003, a new calculation based on a global digital elevation model obtained from satellite measurements, ETOPO2,  whose data points are spaced 2′ (3.7 km at the equator) led to the result ♁ 41°  N, 35°  E and thus validating Wood's calculation. Differentiation from other definitions and calculations 

Various definitions of geographical centres exists. The definition used by the references in this article refer to calculations within the 2 dimensions of a surface, mainly as the surface of Earth is the domain of human cultural existence. Other definitions refer to calculations based on three-dimensional objects, for example the Newtonian gravity centre of the whole Earth (physical barycentre) or the Newtonian gravity centre of only the continents as uniform thick three-dimensional objects. Those centres can be found inside Earth mostly near its core. A projection of those centres towards the surface would be then an alternative definition of the geographical centre, some of those calculations result in a surface location projection not that far away from the geographical centre. See also 
 Centre of the universe (disambiguation)
 Center of population
 Center of the World
 History of the centre of the Universe
 Land and water hemispheres
 Omphalos of Delphi (ancient Greeks' navel of the Earth)

References 

Earth