Editing Map projection (section)

== Suitability of projections for application ==

The mathematics of projection do not permit any particular map projection to be best for everything.<ref name="Enlarging" /> Something will always be distorted. Thus, many projections exist to serve the many uses of maps and their vast range of scales.

Modern national mapping systems typically employ a [[Transverse Mercator projection|transverse Mercator]] or close variant for [[Scale (map)#Large scale, medium scale, small scale|large-scale maps]] in order to preserve [[Conformal map|conformality]] and low variation in scale over small areas. For [[Scale (map)#Large scale, medium scale, small scale|smaller-scale]] maps, such as those spanning continents or the entire world, many projections are in common use according to their fitness for the purpose, such as [[Winkel tripel projection|Winkel tripel]], [[Robinson projection|Robinson]] and [[Mollweide projection|Mollweide]].<ref name="choosing">{{cite book
  | title     = Choosing a World Map
  | publisher = American Congress on Surveying and Mapping
  | year      = 1988
  | isbn      = 0-9613459-2-6
  | location  = Falls Church, Virginia
  | page      = 1
  }}</ref>  Reference maps of the world often appear on [[#Compromise projections|compromise projections]]. Due to distortions inherent in any map of the world, the choice of projection becomes largely one of aesthetics.

Thematic maps normally require an [[#Equal-area|equal area projection]] so that phenomena per unit area are shown in correct proportion.<ref name="slocum">{{cite book
  | title     = Thematic Cartography and Geographic Visualization
  | last      = Slocum
  | first     = Terry A.
  | author2   = Robert B. McMaster
  | author3   = Fritz C. Kessler
  | author4   = Hugh H. Howard
  | publisher = Pearson Prentice Hall
  | year      = 2005
  | isbn      = 0-13-035123-7
  | edition   = 2nd
  | location  = Upper Saddle River, NJ
  | page      = 166
  }}</ref>
However, representing area ratios correctly necessarily distorts shapes more than many maps that are not equal-area.

The [[Mercator projection]], developed for navigational purposes, has often been used in world maps where other projections would have been more appropriate.<ref name="Bauer">Bauer, H.A. (1942). "Globes, Maps, and Skyways (Air Education Series)". New York. p. 28</ref><ref name="Miller">{{cite journal
  | last1   = Miller
  | first1  = Osborn Maitland
  | year    = 1942
  | title   = Notes on Cylindrical World Map Projections
  | journal = Geographical Review
  | volume  = 32
  | issue   = 3
  | pages   = 424–430
  | doi     = 10.2307/210384
  | jstor = 210384
 }}</ref><ref name="Raisz">Raisz, Erwin Josephus. (1938). ''General Cartography''. New York: McGraw–Hill. 2d ed., 1948. p. 87.</ref><ref name="RobinsonElements">Robinson, Arthur Howard. (1960). ''Elements of Cartography'', second edition. New York: John Wiley and Sons. p. 82.</ref> This problem has long been recognized even outside professional circles. For example, a 1943 ''[[New York Times]]'' editorial states:

{{quote|The time has come to discard [the Mercator] for something that represents the continents and directions less deceptively ... Although its usage ... has diminished ... it is still highly popular as a wall map apparently in part because, as a rectangular map, it fills a rectangular wall space with more map, and clearly because its familiarity breeds more popularity.<ref name="SnyderFlattening"/>{{rp|166}}}}

A controversy in the 1980s over the [[Peters map]] motivated the American Cartographic Association (now the [[Cartography and Geographic Information Society]]) to produce a series of booklets (including ''Which Map Is Best''<ref name="ACA1986">American Cartographic Association's Committee on Map Projections, 1986. ''Which Map is Best'' p. 12. Falls Church: American Congress on Surveying and Mapping.</ref>) designed to educate the public about map projections and distortion in maps. In 1989 and 1990, after some internal debate, seven North American geographic organizations adopted a resolution recommending against using any rectangular projection (including Mercator and Gall–Peters) for reference maps of the world.<ref name="Robinson">{{cite journal
  | last1   = Robinson
  | first1  = Arthur
  | year    = 1990
  | title   = Rectangular World Maps—No!
  | journal = Professional Geographer
  | volume  = 42
  | issue   = 1
  | pages   = 101–104
  | doi     = 10.1111/j.0033-0124.1990.00101.x
  }}</ref><ref name="AmericanCartographer">{{cite journal
  | title   = Geographers and Cartographers Urge End to Popular Use of Rectangular Maps
  | doi     = 10.1559/152304089783814089
  | journal = American Cartographer
  | year    = 1989
  | volume  = 16
  | pages   = 222–223
  }}</ref>