Editing Map projection (section)

==Classification==
One way to classify map projections is based on the type of surface onto which the globe is projected. In this scheme, the projection process is described as placing a hypothetical projection surface the size of the desired study area in contact with part of the Earth, transferring features of the Earth's surface onto the projection surface, then unraveling and scaling the projection surface into a flat map. The most common projection surfaces are cylindrical (e.g., [[Mercator projection|Mercator]]), conic (e.g., [[Albers projection|Albers]]), and planar (e.g., [[Stereographic projection in cartography|stereographic]]). Many mathematical projections, however, do not neatly fit into any of these three projection methods. Hence other peer categories have been described in the literature, such as pseudoconic, pseudocylindrical, pseudoazimuthal, retroazimuthal, and [[Polyconic projection|polyconic]].

Another way to classify projections is according to properties of the model they preserve. Some of the more common categories are:
* Preserving direction (''azimuthal or zenithal''), a trait possible only from one or two points to every other point<ref name="WorkingManual">{{cite book
  | first      = John Parr
  | last       = Snyder
  |author-link = John P. Snyder
  | title = Map projections: A working manual
 | publisher  = United States Government Printing Office
  | date       = 1987
  | isbn       = 9780318235622
  | doi        = 10.3133/pp1395
  | doi-access = free
  | series     = United States Geological Survey Professional Paper
  | volume     = 1395
  }}</ref>{{rp|p=192}}
* Preserving shape locally (''[[#Conformal|conformal]]'' or ''orthomorphic'')
* Preserving area (''equal-area'' or ''equiareal'' or ''equivalent'' or ''authalic'')
* Preserving distance (''equidistant''), a trait possible only between one or two points and every other point
* Preserving shortest route, a trait preserved only by the [[gnomonic projection]]
Because the sphere is not a [[developable surface]], it is impossible to construct a map projection that is both equal-area and conformal.