Two-point equidistant projection

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Two-point equidistant projection of Asia. All distances are correct from the two points (45degN, 40degE) and (30degN, 110degE). Two-point equidistant projection SW.jpg
Two-point equidistant projection of Asia. All distances are correct from the two points (45°N, 40°E) and (30°N, 110°E).
Two-point equidistant projection of the entire world with Tissot's indicatrix of deformation. The two points are Rome, Italy and Luoyang, China. Two-point Equidistant with Tissot's Indicatrices of Distortion.svg
Two-point equidistant projection of the entire world with Tissot's indicatrix of deformation. The two points are Rome, Italy and Luoyang, China.

The two-point equidistant projection is a map projection first described by Hans Maurer in 1919. It is a generalization of the much simpler azimuthal equidistant projection. In this two-point form, two locus points are chosen by the mapmaker to configure the projection. Distances from the two loci to any other point on the map are correct: that is, they scale to the distances of the same points on the sphere.

Map projection Systematic representation of the surface of a sphere or ellipsoid onto a plane

A map projection is a systematic transformation of the latitudes and longitudes of locations from the surface of a sphere or an ellipsoid into locations on a plane. Maps cannot be created without map projections. All map projections necessarily distort the surface in some fashion. Depending on the purpose of the map, some distortions are acceptable and others are not; therefore, different map projections exist in order to preserve some properties of the sphere-like body at the expense of other properties. There is no limit to the number of possible map projections.

Azimuthal equidistant projection azimuthal map projection

The azimuthal equidistant projection is an azimuthal map projection. It has the useful properties that all points on the map are at proportionally correct distances from the center point, and that all points on the map are at the correct azimuth (direction) from the center point. A useful application for this type of projection is a polar projection which shows all meridians as straight, with distances from the pole represented correctly. The flag of the United Nations contains an example of a polar azimuthal equidistant projection.

Locus (mathematics) set of points whose location satisfies or is determined by one or more specified conditions

In geometry, a locus is a set of all points, whose location satisfies or is determined by one or more specified conditions.

The projection has been used for all maps of the Asian continent by the National Geographic Society atlases since 1959, [1] though its purpose in that case was to reduce distortion throughout Asia rather than to measure from the two loci. [2] The projection sometimes appears in maps of air routes. The Chamberlin trimetric projection is a logical extension of the two-point idea to three points, but the three-point case only yields a sort of minimum error for distances from the three loci, rather than yielding correct distances. Tobler extended this idea to arbitrarily large number of loci by using automated root-mean-square minimization techniques rather than using closed-form formulae.[ citation needed ]

National Geographic Society American non-profit scientific and educational institution

The National Geographic Society (NGS), headquartered in Washington, D.C., United States, is one of the largest non-profit scientific and educational organizations in the world. Founded in 1888, its interests include geography, archaeology, and natural science, the promotion of environmental and historical conservation, and the study of world culture and history. The National Geographic Society's logo is a yellow portrait frame—rectangular in shape—which appears on the margins surrounding the front covers of its magazines and as its television channel logo. Through National Geographic Partners, the Society operates the magazine, TV channels, a website, worldwide events, and other media operations.

Chamberlin trimetric projection

The Chamberlin trimetric projection is a map projection where three points are fixed on the globe and the points on the sphere are mapped onto a plane by triangulation. It was developed in 1946 by Wellman Chamberlin for the National Geographic Society. Chamberlin was chief cartographer for the Society from 1964 to 1971. The projection's principal feature is that it compromises between distortions of area, direction, and distance. A Chamberlin trimetric map therefore gives an excellent overall sense of the region being mapped. Many National Geographic Society maps of single continents use this projection.

In mathematics and its applications, the root mean square is defined as the square root of the mean square . The RMS is also known as the quadratic mean and is a particular case of the generalized mean with exponent 2. RMS can also be defined for a continuously varying function in terms of an integral of the squares of the instantaneous values during a cycle.

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Gall–Peters projection specialization of a configurable equal-area map projection

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Latitude The angle between zenith at a point and the plane of the equator

In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle which ranges from 0° at the Equator to 90° at the poles. Lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude is used together with longitude to specify the precise location of features on the surface of the Earth. On its own, the term latitude should be taken to be the geodetic latitude as defined below. Briefly, geodetic latitude at a point is the angle formed by the vector perpendicular to the ellipsoidal surface from that point, and the equatorial plane. Also defined are six auxiliary latitudes which are used in special applications.

Mercator projection map projection

The Mercator projection is a cylindrical map projection presented by the Flemish geographer and cartographer Gerardus Mercator in 1569. It became the standard map projection for navigation because of its unique property of representing any course of constant bearing as a straight segment. Such a course, known as a rhumb or, mathematically, a loxodrome, is preferred by navigators because the ship can sail in a constant compass direction to reach its destination, eliminating difficult and error-prone course corrections. Linear scale is constant on the Mercator in every direction around any point, thus preserving the angles and the shapes of small objects and fulfilling the conditions of a conformal map projection. As a side effect, the Mercator projection inflates the size of objects away from the equator. This inflation starts infinitesimally but accelerates with latitude to reach infinite at the poles. So, for example, landmasses such as Greenland and Antarctica appear far larger than they actually are relative to landmasses near the equator, such as Central Africa.

Geographic coordinate system Coordinate system

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Dymaxion map map projection

The Dymaxion map or Fuller map is a projection of a world map onto the surface of an icosahedron, which can be unfolded and flattened to two dimensions. The flat map is heavily interrupted in order to preserve shapes and sizes.

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World map map of the surface of the Earth

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Afro-Eurasia major landmass on Earth consisting of Africa, Asia and Europe

Afro-Eurasia is a landmass which comprises the continents of Africa and Eurasia. The terms are portmanteaus of the names of its constituent parts. Its mainland is the largest contiguous landmass on Earth.

Equidistant conic projection conic map projection

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  1. Snyder, J.P. (1993). Flattening the Earth: 2,000 years of map projections. pp. 234–235. ISBN   0226767469.
  2. "Portrait of Earth's largest continent", National Geographic Magazine, vol. 116 no. 6, p. 751, 1959