Pole of inaccessibility

The northern pole of inaccessibility, sometimes known as the Arctic pole, is located on the Arctic Ocean pack ice at a distance farthest from any landmass. The original position was wrongly believed to lie at 84°3′N 174°51′W. It is not clear who first defined this point, but it may have been Sir Hubert Wilkins, who wished to traverse the Arctic Ocean by aircraft in 1927. He was finally successful in 1928. In 1968 Sir Wally Herbert came very close to reaching what was then considered to be the position by dogsled, but by his own account, Across the Top of the World, did not make it due to the flow of sea ice. In 1986, an expedition of Soviet polar scientists led by Dmitry Shparo claimed to reach the original position by foot during a polar night. In 2005, explorer Jim McNeill asked scientists from The National Snow and Ice Data Center and Scott Polar Research Institute to re-establish the position using modern GPS and satellite technology. This was published as a paper in the Polar Record, Cambridge University Press in 2013. In 2010 he and his Ice Warrior team were thwarted again by the poor condition of the sea ice. The new position lies at , from the three closest landmasses: Henrietta Island in the De Long Islands, at Arctic Cape on Severnaya Zemlya, and on Ellesmere Island. It is over from the originally accepted position. Due to constant motion of the pack ice, no permanent structure can exist at this pole. On 12 September 2024, the French icebreaking cruise ship Le Commandant Charcot became the first ship to reach the Northern Pole of Inaccessibility. ==Southern pole of inaccessibility==

on 19 January 2007 The southern pole of inaccessibility is the point on the Antarctic continent most distant from the Southern Ocean. A variety of coordinate locations have been given for this pole. The discrepancies are due to the question of whether the "coast" is measured to the grounding line or the edges of ice shelves, the difficulty of determining the location of the "solid" coastline, the movement of ice sheets and improvements in the accuracy of survey data over the years, as well as possible topographical errors. The point commonly referred to as the pole of inaccessibility is the site of the Soviet Union research station mentioned below, which was constructed at (though some sources give ). This lies from the South Pole, at an elevation of . Using different criteria, the Scott Polar Research Institute locates this pole at . Using recent datasets and cross-confirmation between the adaptive gridding and B9-Hillclimbing On 4 December 2006, Team N2i, consisting of Henry Cookson, Rupert Longsdon, Rory Sweet and Paul Landry, embarked on an expedition to be the first to reach the historic pole of inaccessibility location without direct mechanical assistance, using a combination of traditional man hauling and kite skiing. The team reached the old abandoned station on 19 January 2007, rediscovering the forgotten statue of Lenin left there by the Soviets some 48 years previously. The team found that only the bust on top of the building remained visible; the rest was buried under the snow. On 27 December 2011, Sebastian Copeland and partner Eric McNair-Laundry also reached the southern pole of inaccessibility. They were the first to do so without resupply or mechanical support, departing from Novolazarevskaya Station on their way to the South Pole to complete the first East/West crossing of Antarctica through both poles, over . As mentioned above, due to improvements in technology and the position of the continental edge of Antarctica being debated, the exact position of the best estimate of the pole of inaccessibility may vary. However, for the convenience of sport expeditions, a fixed point is preferred, and the Soviet station has been used for this role. This has been recognized by Guinness World Records for Team N2i's expedition in 2006–2007. ==Oceanic pole of inaccessibility==

The oceanic pole of inaccessibility, also known as Point Nemo, is located at roughly and is the place in the ocean that is farthest from land. It represents the solution to the "longest swim" problem. The problem entails finding such a place in the world ocean where, if a person fell overboard while on a ship at sea, they would be as far away from any land in any direction as possible. It lies in the South Pacific Ocean, and is equally distant from the three closest land vertices which are each roughly away. Those vertices are Pandora Islet of the Ducie Island atoll (an island of the Pitcairn Islands) to the north; Motu Nui (adjacent to Easter Island) to the northeast; and Maher Island (near the larger Siple Island, off the coast of Marie Byrd Land, Antarctica) to the south. The antipode of Point Nemo – the point on the surface of the Earth that is diametrically opposite of it – is located at roughly , in the Aktobe Region of western Kazakhstan, roughly 50 km (30 miles) SSE of the town of Shubarkuduk. Point Nemo is relatively lifeless; its location within the South Pacific Gyre blocks nutrients from reaching the area, and being so far from land it gets little nutrient run-off from coastal waters. To the west the region of the South Pacific Ocean is also the site of the geographic center of the water hemisphere, at near New Zealand's Bounty Islands. The geographic center of the Pacific Ocean lies further north-west where the Line Islands begin, west from Starbuck Island at . History Point Nemo was first identified by Croatian survey engineer in 1992. The general area plays a major role in the 1928 short story "The Call of Cthulhu" by H. P. Lovecraft, as holding the location of the fictional city of R'lyeh, although this story was written 66 years before the identification of Point Nemo. or maritime traffic. The International Space Station (ISS) is planned to crash into Point Nemo in 2031. ==Continental poles of inaccessibility==

Eurasia The Eurasian pole of inaccessibility (EPIA) is located in northwestern China, near the Kazakhstan border. It is also the farthest possible point on land from the ocean anywhere on Earth. However, Eurasia (or even Asia alone) being the largest continent does not necessarily mean that its pole of inaccessibility is the farthest from the ocean anywhere. Earlier calculations suggested that it is from the nearest coastline, located at , approximately north of the city of Ürümqi, in the Xinjiang Autonomous Region of China, in the Gurbantünggüt Desert. The nearest settlements to this location are Hoxtolgay Town at , about to the northwest, Xazgat Township () at , about to the west, and Suluk at , about to the east. However, the previous pole location disregards the Gulf of Ob as part of the oceans, and a 2007 study and a monument to this effect was erected there in the 1990s. The site is a local tourist attraction. Coincidentally, the continental and oceanic poles of inaccessibility have a similar radius; the Eurasian poles EPIA1 and EPIA2 are about closer to the ocean than the oceanic pole is to land. Africa In Africa, the pole of inaccessibility is at , from the coast, The pole was marked in 2021 with a marker that represents the 7 Lakota Values and the four colors of the Lakota Medicine Wheel. South America In South America, the continental pole of inaccessibility is in Brazil at , near Arenápolis, Mato Grosso, In 2019, it was discovered that there is a second South American pole of inaccessibility to the north, its position varying greatly between the two coastline datasets used. Australia In Australia, the continental pole of inaccessibility is located at from the nearest coastline, approximately 161 km (100 miles) west-northwest of Alice Springs. The nearest town is Papunya, Northern Territory, about west-southwest of the pole. ==Methods of calculation==

As detailed below, several factors determine how a pole is calculated using computer modeling. Poles are calculated with respect to a particular coastline dataset. Currently used datasets are the GSHHG (Global Self-consistent, Hierarchical, High-resolution Geography Database) as well as OpenStreetMap (OSM) planet dumps. The GSHHG claims 500-meter precision for 90% of identifiable coastal features, while the volunteer-built OSM gives no such guarantee but nevertheless has "characteristics suggesting accuracy". Next, a distance function must be determined for calculating distances between coastlines and potential Poles. Some works tended to project data onto planes or perform spherical calculations; more recently, other works have used different algorithms and high-performance computing with ellipsoidal calculations. Finally, an optimization algorithm must be developed. Several works use the 2007 adaptive grid method of Garcia-Castellanos and Lombardo. In this method, a rectangular grid of, e.g., 21×21 points is created. Each point's distance from the coastline is determined and the point farthest from the coast identified. The grid is then recentered on this point and shrunk by some factor. This process iterates until the grid becomes very small (e.g. at 100-meter precision). Some authors claim this method could sink into a local minimum. A more recent method from 2019, B9-Hillclimbing by Barnes, uses a polyhedron in 3D space to find initial points evenly spaced by 100 kilometers. These points are then grouped; the more "unique" points are subject to numerical optimization (hill climbing, simulated annealing) for the farthest distance, accelerated by a 3D Cartesian point cloud. Rees (2021) shows that the two methods agree with each other to meter level. To date, there has been no meta-study of the various works and their algorithms and datasets. However, successive works have compared themselves with previous calculations and claimed improvement. For example, the GC & L article from 2007 was able to find hundred-kilometer errors in the "traditional" Eurasian PIA in Crane & Crane, 1987. Rees, using the same method, updated the arctic PIA by over 200 kilometers. Barnes, which improved upon the method and the dataset used, was able to improve the GC & L South American PIA by 50 kilometers, showing that bad coastline data caused an error of 57 kilometers in their reported PIA-to-coast distance. ==List of poles of inaccessibility==

Poles of Inaccessibility, as determined by some authors, are listed in the table below. This list is incomplete and may not capture all works done to date. ArcGIS personnel wrote a 2015 page with their calculations based on a flat Earth. The results are too inaccurate to be included here. ==See also==