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The geographical centre of Earth is the geometric centre of all land surfaces on Earth. In a more strict definition, it is the superficial barycenter of the mass distribution produced by treating each continent or island as a region of a thin shell of uniform density and approximating the geoid with a sphere. == History of geo-centroid calculation == 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 addition, in October of that year, Smyth attempted to have the Great Pyramid be labeled as the prime meridian because that location meant it would "pass over more land than any other". 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".〔 Referring to Smyth's book, Frederick Augustus Porter Barnard wrote in his 1884 book, ''The imaginary metrological system of the Great pyramid of Gizeh'', that the perfect location of the Great Pyramid along the longitudinal line could only have been purposefully done by its builders. In the September 1919 issue of ''Trestle Board Magazine'', Mason William Galliher stated that knowledge of the Great Pyramid being the geographical center was "determined by many years of scientific investigation" and that the Great Pyramid was likely to be the "last of the present land surface of the earth" to survive a cataclysmic event, due to its positioning. However, in 2007, Susan Wise Bauer claimed in her book '' Earliest Accounts to the Fall of Rome'', that the theory that the Great Pyramid was the geographical centre of Earth would only hold true if a Mercator projection is used as the map for Earth, which was "unlikely to have been a common practice of the ancient Egyptians". In 1973, Andrew J. Woods, a physicist with Gulf Energy & Environmental Systems in San Diego, used a digital global map and calculated the coordinates on a mainframe system as , 1000 km north of Giza and 150 km southeast of Ankara, Turkey. In 2003, a revised calculation by Holger Isenberg using the higher resolution ETOPO2〔(【引用サイトリンク】title=ETOPO2 Global Gridded 2-minute Database )〕 global digital elevation model (DEM) with data points every 2' (3.7 km near equator) led to a more precise result of (180 km northeast of Ankara) and thereby validated Woods' calculation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Geographical centre of Earth」の詳細全文を読む スポンサード リンク
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