Geographical centre of Earth

The geographic center of the earth's surface is the geometric centroid of all land areas of the earth.

Formulated geometrically exact, it is the centroid within the two-dimensional spherical surface of the earth, with a simplistic geoid is assumed as a geometric shape and the relief structure of the rural areas are idealized as flat planes. For calculating a centroid of a definition of removal is necessary, which is placed on the earth's surface as the shortest distance between two points on the major arc of a circle. The real distance between two points on the earth is thus clearly and independently of any map projection.

The term is not the geometric center of the earth is meant a three-dimensional body, as is within the earth's core.

Calculation method

The geographical focus is clearly the point on the Earth's surface, from which the sum of the distances to all other points on land is minimal. The determination can not mathematically analytically, so done " in one step " because no mathematical abstraction of the shape of the continents and islands of the earth exist, but need to be applied iteratively numerically. The commonly used method divides a digital earth model into grid points calculated for each grid point whose distances to all other grid points and adds them up. The point whose distance sum is minimal, is the geographic center.

Using the same calculation method for example, the population center was determined, only the local population density was there in addition as the basis consulted.

History of computing

In 1864, Charles Piazzi Smyth was Director of the Scottish Royal Observatory of Edinburgh, in his book Our Inheritance in the Great Pyramid with the coordinates 30 ° 0 ' N, 31 ° 0' O3031, which corresponds to the position of the pyramids of Giza. In October of the same year added Smyth to declare the Great Pyramid as Prime Meridian can, that this is the meridian that runs in comparison to all others, the greatest line coverage over land areas. He also emphasized the cultural importance of this position with its proximity to Jerusalem. However, the former decision-making body for the selection of the prime meridian then chose in 1884 the position of the Royal Greenwich Observatory in London because map navigation time mainly used for nautical navigation and London was the most important international port. On referring Smyth, Frederick Augustus Porter Barnard wrote (1809-1889) in 1884 in The imaginary metrological system of the Great pyramid of Giza, the perfect positioning of the Great Pyramid along the meridian points to a proposed decision of its builders.

In the issue of September 1919 the American Trestle Board Magazine, said William Galliher that knowledge, the Great Pyramid is the geographical center of all the land was " due to many years of scientific research strengthened " and that the current position of the Great Pyramid is probably the " final place on earth " is to survive a cataclysmic event.

In 1973, Andrew J. Woods used, a physicist at Gulf Energy and Environmental Systems Company in San Diego, a global digital map to calculate the coordinates on a mainframe system algorithmically. The result was 39 ° 0 ' N, 34 ° 0' O3934 1000 km north of Giza and 300 km east of the specified Smyth longitude.

In 2003, a new calculation based on a value obtained by satellite measurements global digital elevation model, ETOPO2 whose data points ' are (3,7 km at the equator), the result of 40 ° 52 ' at a distance of 2 N, 34 ° 34' O40. 86666666666734.566666666667 and thus validated Woods calculation.

Criticism

The calculation of the geographical center is dependent on the type of map projection: the position of the center near the center of the world maps commonly used in Europe and the U.S. by selecting the map section appears limited at first glance. In the era before the invention of the computer, the center was actually often determined on the basis of graphical work on maps in cylindrical projection. Thus, the conditional in any map projection imaging errors on the calculation and distance computations on the edge of the card is also transferred were probably not performed. Nowadays, the calculation is performed independently of each card on the direct determination of distances along great circle arcs. The computer program uses a digital globe model, ie a " borderless map ". The only significant error arises due to the simplification of the shape of the surface of the earth, but this deviation is so minimal that it can be neglected.

The calculation would ignore the surface relief of the earth, so their mountains and valleys: The distance between the highest point on the earth's surface above sea level and the lowest land sink within continents is 10 km. To illustrate this minimum error once vividly: 10 km are 0.08 % of the diameter of the Earth, is 12.7 thousand km, thus ignoring the surface detail is justified.

The choice of the selected algorithm for the calculation is arbitrary: The selected algorithm is the usual method to determine centers of irregular surfaces. Considered an idealized example, it is the process within the business discipline, Operations Research, to determine the optimal location of a distribution warehouse of a company if only a central warehouse exists and delivery targets are spread throughout the area.