Global InformationMap projection information
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] Projection is a necessary step in creating a two-dimensional map and is one of the essential elements of cartography.
All projections of a sphere on a plane necessarily distort the surface in some way and to some extent.[6] 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. The study of map projections is primarily about the characterization of their distortions. There is no limit to the number of possible map projections.[7]: 1 More generally, projections are considered in several fields of pure mathematics, including differential geometry, projective geometry, and manifolds. However, the term "map projection" refers specifically to a cartographic projection.
Despite the name's literal meaning, projection is not limited to perspective projections, such as those resulting from casting a shadow on a screen, or the rectilinear image produced by a pinhole camera on a flat film plate. Rather, any mathematical function that transforms coordinates from the curved surface distinctly and smoothly to the plane is a projection. Few projections in practical use are perspective.[citation needed]
Most of this article assumes that the surface to be mapped is that of a sphere. The Earth and other large celestial bodies are generally better modeled as oblate spheroids, whereas small objects such as asteroids often have irregular shapes. The surfaces of planetary bodies can be mapped even if they are too irregular to be modeled well with a sphere or ellipsoid.[8] Therefore, more generally, a map projection is any method of flattening a continuous curved surface onto a plane.[citation needed]
The most well-known map projection is the Mercator projection.[7]: 45 This map projection has the property of being conformal. However, it has been criticized throughout the 20th century for enlarging regions further from the equator.[7]: 156–157 To contrast, equal-area projections such as the Sinusoidal projection and the Gall–Peters projection show the correct sizes of countries relative to each other, but distort angles. The National Geographic Society and most atlases favor map projections that compromise between area and angular distortion, such as the Robinson projection and the Winkel tripel projection.[7][9]
- ^ Lambert, Johann; Tobler, Waldo (2011). Notes and comments on the composition of terrestrial and celestial maps. Redlands, CA: ESRI Press. ISBN 978-1-58948-281-4.
- ^ Richardus, Peter; Adler, Ron (1972). map projections. New York, NY: American Elsevier Publishing Company, inc. ISBN 0-444-10362-7.
- ^ Robinson, Arthur; Randall, Sale; Morrison, Joel; Muehrcke, Phillip (1985). Elements of Cartography (fifth ed.). Wiley. ISBN 0-471-09877-9.
- ^ Snyder, J.P.; Voxland, P.M. (1989). "An album of map projections". Album of Map Projections (PDF). U.S. Geological Survey Professional Paper. Vol. 1453. United States Government Printing Office. doi:10.3133/pp1453. Retrieved 8 March 2022.
- ^ Ghaderpour, E. (2016). "Some equal-area, conformal and conventional map projections: a tutorial review". Journal of Applied Geodesy. 10 (3): 197–209. arXiv:1412.7690. Bibcode:2016JAGeo..10..197G. doi:10.1515/jag-2015-0033. S2CID 124618009.
- ^ Monmonier, Mark (2018). How to lie with maps (3rd ed.). The University of Chicago Press. ISBN 978-0-226-43592-3.
- ^ a b c d Snyder, John P. (1993). Flattening the earth: two thousand years of map projections. University of Chicago Press. ISBN 0-226-76746-9.
- ^ Hargitai, Henrik; Wang, Jue; Stooke, Philip J.; Karachevtseva, Irina; Kereszturi, Akos; Gede, Mátyás (2017), Map Projections in Planetary Cartography, Lecture Notes in Geoinformation and Cartography, Springer International Publishing, pp. 177–202, doi:10.1007/978-3-319-51835-0_7, ISBN 978-3-319-51834-3
- ^ Singh, Ishveena (25 April 2017). "Which is the best map projection?". Geoawesomeness.