A fact: No map can provide an accurate image of our planet (or any part of it). The reason: there can be no way to accurately simulate the surface of a sphere on a flat surface.
A map projection is any method of representing the surface of a sphere or other shape on a plane. Map projections are necessary for creating maps. All map projections distort the surface in some fashion. 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. There is no limit to the number of possible map projections.
Many properties can be measured on the Earth's surface independently of its geography. Some of these properties are:
- Area
- Shape
- Direction
- Bearing
- Distance
- Scale
Map projections can be constructed to preserve one or more of these properties, though not all of them simultaneously. Each projection preserves or compromises or approximates basic metric properties in different ways. The purpose of the map determines which projection should form the base for the map. Because many purposes exist for maps, many projections have been created to suit those purposes.
Most of us are familiar with the Mercator projection, though it is fundamentally wrong (Greenland, for instance, appears to be huge -roughly the same size with S.America-while is only one fifth of the size of South America). Another projection which gained some popularity in the 60's was the Gaul-Peter projection. Like the one below:
The American Cartographic Association adopted the following resolution which rejected all rectangular world maps, a category that includes both the Mercator and the Gall–Peters projections:
Types of Map projectionsWHEREAS, the earth is round with a coordinate system composed entirely of circles, and
WHEREAS, flat world maps are more useful than globe maps, but flattening the globe surface necessarily greatly changes the appearance of Earth's features and coordinate systems, and
WHEREAS, world maps have a powerful and lasting effect on people's impressions of the shapes and sizes of lands and seas, their arrangement, and the nature of the coordinate system, and
WHEREAS, frequently seeing a greatly distorted map tends to make it "look right,"
THEREFORE, we strongly urge book and map publishers, the media and government agencies to cease using rectangular world maps for general purposes or artistic displays. Such maps promote serious, erroneous conceptions by severely distorting large sections of the world, by showing the round Earth as having straight edges and sharp corners, by representing most distances and direct routes incorrectly, and by portraying the circular coordinate system as a squared grid. The most widely displayed rectangular world map is the Mercator (in fact a navigational diagram devised for nautical charts), but other rectangular world maps proposed as replacements for the Mercator also display a greatly distorted image of the spherical Earth.
A. Projections by surface
- Cylindrical (like Mercator and Gaul-Peters)
- Pseudocylindrical
- Hybrid
- Conical
- Pseudoconical
- Azimuthal (directions from a central point are preserved (and hence, great circles through the central point are represented by straight lines on the map)). There are many subtypes like the gnomonic projection, orthographic projection, the Azimuthal equidistant etc.
- Conformal (projections preserve angles locally), like Mercator
- Equal-area (preserve area), like Gaul-Peter
- Equidistant (preserve distance from some standard point or line)
- Gnomonic(Great circles are displayed as straight lines)
- Compromise projections ( give up the idea of perfectly preserving metric properties, seeking instead to strike a balance between distortions). Most maps are used today belong in this category. Especially into the subtypes: Robinson projection and the Winkel Tripel projection which is preferred by National Geographic.(like the one in the beginning of the post)
