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In cartography, a map projection is any of a broad set of transformations employed to represent the curved two-dimensional surface of a globe on a plane. [ 1][ 2][ 3] In a map projection, coordinates, often expressed as latitude and longitude, of locations from the surface of the globe are transformed to coordinates on a plane. [ 4][ 5 ...
and λ is the longitude, λ 0 is the central meridian, φ is the latitude, and R is the radius of the globe to be projected. The map has area 4 π R 2, conforming to the surface area of the generating globe. The x-coordinate has a range of [−2R √ 2, 2R √ 2], and the y-coordinate has a range of [−R √ 2, R √ 2].
The great-circle distance, orthodromic distance, or spherical distance is the distance between two points on a sphere, measured along the great-circle arc between them. This arc is the shortest path between the two points on the surface of the sphere. (By comparison, the shortest path passing through the sphere's interior is the chord between ...
Geodetic latitude and geocentric latitude have different definitions. Geodetic latitude is defined as the angle between the equatorial plane and the surface normal at a point on the ellipsoid, whereas geocentric latitude is defined as the angle between the equatorial plane and a radial line connecting the centre of the ellipsoid to a point on the surface (see figure).
Null Island is the location at zero degrees latitude and zero degrees longitude ( 0°N 0°E ), i.e., where the prime meridian and the equator intersect. The name is often used in mapping software as a placeholder to help find and correct database entries that have erroneously been assigned the coordinates 0,0.
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.
The most common horizontal position representation is latitude and longitude. The parameters are intuitive and well known, and are thus suited for communicating a position to humans, e.g. using a position plot. However, latitude and longitude should be used with care in mathematical expressions (including calculations in computer programs).
Galactic coordinate system. Artist's depiction of the Milky Way Galaxy showing the origin and orientation of galactic longitude. The galactic longitude ( l) runs from the Sun upwards in the image through the center of the galaxy. The galactic latitude ( b) is perpendicular to the image (i.e. coming out of the image) and also centered on the Sun.