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In astronomy and navigation, the celestial sphere is an imaginary rotating sphere of "gigantic radius", concentric and coaxial with the Earth. All objects in the sky can be thought of as lying upon the sphere. Projected from their corresponding geographic equivalents are the celestial equator and the celestial poles. The celestial sphere projection is a very practical tool for positional astronomy. In the Aristotelic and Ptolemaic models, the celestial sphere was imagined as a physical reality rather than a geometrical projection (see Celestial spheres).

Parallax effects

The celestial sphere can be used geocentrically and topocentrically. The former means that it is centred upon an imaginary observer in the centre of the Earth, and no parallax effects need to be taken into account. In the latter case it is centred upon an observer on the surface of the Earth and then horizontal parallax cannot always be ignored; especially not for the Moon.

Celestial hemispheres

Arthur H. Robinson (January 5, 1915 – October 10, 2004) was an American geographer and cartographer, who was professor in the Geography Department at the University of Wisconsin in Madison from 1947 until he retired in 1980. He was a prolific writer and influential philosopher on cartography, and one of his most notable accomplishments is the Robinson projection in 1961.

Biography

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 nautical purposes because of its ability to represent lines of constant course, known as rhumb lines or loxodromes, as straight segments. While the linear scale is constant in all directions around any point, thus preserving the angles and the shapes of small objects (which makes the projection conformal), the Mercator projection distorts the size and shape of large objects, as the scale increases from the Equator to the poles, where it becomes infinite.

Properties and historical details

Erwin Josephus Raisz (1893-1968) was a distinguished, influential cartographer who helped pioneer and standardize the field of modern cartography in the 20th century with his 1938 publication of General Cartography (McGraw Hill), the first complete textbook on cartography written in English. Mr. Raisz was born in Hungary. As the son of a civil engineer, he was introduced to maps and their uses when his father took him on assignments in his youth. He was acclaimed for his unique artistic style, and in the course of his career created a substantial number of visually appealing hand-drawn maps and detailed geomorphological and landform sketches.

The Dymaxion Map of the Earth, also known as the Fuller Projection, is a projection of a global map onto the surface of a polyhedron, which, when expanded to a flat, two-dimensional map, retains most of the relative proportional integrity (relative size and shape) of global features. The Dymaxion Map is the most well known flat map of the entire surface of the earth that reveals virtually contiguous continents as an island in one ocean, without any visible distortion of the relative shapes and sizes of the land areas.

The Dymaxion Map projection was created by the visionary designer and inventor Buckminster Fuller and patented in 1946. The 1954 version published by Fuller under the title The Air-Ocean World Map used a slightly modified but mostly regular icosahedron as the base for the projection, and this is the version most commonly referred to today.

The Esri Shapefile or simply a shapefile is a popular geospatial vector data format for geographic information systems software. It is developed and regulated by Esri as a (mostly) open specification for data interoperability among Esri and other software products. A "shapefile" commonly refers to a collection of files with "", "", "", and other extensions on a common prefix name (e.g., ""). The actual shapefile relates specifically to files with the "" extension, however this file alone is incomplete for distribution, as the other supporting files are required. Shapefiles spatially describe geometries: points, polylines, and polygons. These, for example, could represent water wells, rivers, and lakes, respectively. Each item may also have attributes that describe the items, such as the name or temperature.

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