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  2. Earth radius - Wikipedia

    en.wikipedia.org/wiki/Earth_radius

    Earth's authalic radius (meaning "equal area") is the radius of a hypothetical perfect sphere that has the same surface area as the reference ellipsoid. The IUGG denotes the authalic radius as R 2. [2] A closed-form solution exists for a spheroid: [8]

  3. Authalic radius - Wikipedia

    en.wikipedia.org/?title=Authalic_radius&redirect=no

    This page was last edited on 5 July 2014, at 02:50 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike License 4.0; additional terms may apply ...

  4. Geodesics on an ellipsoid - Wikipedia

    en.wikipedia.org/wiki/Geodesics_on_an_ellipsoid

    The study of geodesics on an ellipsoid arose in connection with geodesy specifically with the solution of triangulation networks. The figure of the Earth is well approximated by an oblate ellipsoid, a slightly flattened sphere. A geodesic is the shortest path between two points on a curved surface, analogous to a straight line on a plane surface.

  5. Equal-area projection - Wikipedia

    en.wikipedia.org/wiki/Equal-area_projection

    In cartography, an equivalent, authalic, or equal-area projection is a map projection that preserves relative area measure between any and all map regions. Equivalent projections are widely used for thematic maps showing scenario distribution such as population, farmland distribution, forested areas, and so forth, because an equal-area map does ...

  6. Geodetic Reference System 1980 - Wikipedia

    en.wikipedia.org/wiki/Geodetic_Reference_System_1980

    The 1980 Geodetic Reference System (GRS 80) posited a 6 378 137 m semi-major axis and a 298.257222101 flattening. This system was adopted at the XVII General Assembly of the International Union of Geodesy and Geophysics (IUGG) in Canberra, Australia, 1979. The GRS 80 reference system was originally used by the World Geodetic System 1984 (WGS 84).

  7. Equivalent radius - Wikipedia

    en.wikipedia.org/wiki/Equivalent_radius

    The authalic radius is an surface area-equivalent radius for solid figures such as an ellipsoid. The osculating circle and osculating sphere define curvature -equivalent radii at a particular point of tangency for plane figures and solid figures, respectively.

  8. AuthaGraph projection - Wikipedia

    en.wikipedia.org/wiki/AuthaGraph_projection

    An approximation of the AuthaGraph projection. AuthaGraph is an approximately equal-area world map projection invented by Japanese architect Hajime Narukawa [1] in 1999. [2] The map is made by equally dividing a spherical surface into 96 triangles, transferring it to a tetrahedron while maintaining area proportions, and unfolding it in the form of a rectangle: it is a polyhedral map projection.

  9. List of map projections - Wikipedia

    en.wikipedia.org/wiki/List_of_map_projections

    Equal-area. Walter Behrmann. Cylindrical equal-area projection with standard parallels at 30°N/S and an aspect ratio of (3/4)π ≈ 2.356. 2002. Hobo–Dyer. Cylindrical. Equal-area. Mick Dyer. Cylindrical equal-area projection with standard parallels at 37.5°N/S and an aspect ratio of 1.977.