We explain what a cartographic projection is, its importance in map creation, and its properties. We also provide examples of different types of projections. Please read other MTV articles for more information. If you share it, it will be of little help to us.
What is a cartographic projection?
A cartographic projection is a tool for representing the curved surface of the Earth on a plane. Because the Earth is a three-dimensional object, any attempt to depict its surface on a map will inevitably present some form of distortion.
This is a procedure specific to map creation by cartographers, who must be guided by the coordinate system comprising the Earth’s parallels and meridians to construct a spatial representation that faithfully reflects the proportions of the planet’s curvature.
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This, however, cannot be done without a certain margin of error, so projections are studied to minimize distortion as much as possible and preserve, in particular, the three fundamental aspects of a map: distances, surfaces, and shapes.
Characteristics of Cartographic Projections
The main characteristics of cartographic projections are:
- They are tools for representing the Earth’s spherical surface on a plane.
- They always produce some distortion in the distances, shapes, or sizes represented.
- There are different types of projections: cylindrical, conic, and azimuthal.
- The Mercator projection is the most widely used worldwide.
Properties of a Cartographic Projection
All cartographic projections have characteristic features that are linked to the type of transformation or the geometric procedure used to create them. Thus, a projection may meet one or two of the following properties, but in no case can it fulfill all three simultaneously:
Equidistance
The projection is faithful to the distances of the original and maintains its proportions at the corresponding scale over most of the map. In some areas, distance distortion is inevitable, and areas and shapes appear altered.
Equivalence
The projection is faithful to the areas of the original surfaces; that is, it does not distort the extent, but the shapes may be modified.
Conformity
The projection is faithful to the shapes and angles of the original; that is, it does not distort the outline or appearance of the represented surface, but the sizes are distorted.
The choice of one cartographic projection or another depends on the specific needs of the map and the geographic properties that are desired to be highlighted or preserved.
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Types of Cartographic Projections
Cartographic projections are generally classified according to the geometric figure that inspires them:
Cylindrical Projections
These projections use an imaginary cylinder as the map surface. These projections more faithfully respect shapes, but as the distance from the equator increases, distances and surfaces become more and more distorted. The Mercator projection, the most widely used worldwide, is a type of cylindrical projection.
Conic Projections
Similar to cylindrical projections, these projections are obtained by placing the Earth’s sphere within the inner curvature of an imaginary cone, onto which the parallels and meridians are projected. These projections convert the meridians into straight lines extending from the pole, and the parallels into concentric circles within the cone. The resulting map is ideal for representing mid-latitudes because distortion increases as one moves toward the poles. An example of a conic projection is the Lambert conic projection.
Azimuthal Projections
Also called zenith projections, they are obtained by placing the Earth’s sphere on an imaginary plane, tangent to the sphere itself (as if looking at the planet from above), onto which the meridians and parallels are projected. These projections are more accurate in high-latitude regions, but exhibit increasing distortion with greater distance from the poles, so they are not used to represent mid-latitudes or the equatorial region.
Examples of Cartographic Projections
The main and best-known cartographic projections are:
Mercator projection
Created by the German geographer and mathematician Gerardus Mercator (1512-1594) in 1569, it is one of the most widely used terrestrial projections in history, especially in the creation of maps for navigation during the 18th century. It is a cylindrical projection that respects the shape of the continents, but noticeably distorts their sizes, especially in regions far from the equator. For this reason, for example, Greenland appears the same size as Africa, when in reality Africa is fifteen times larger.
Lambert projection
Also called the “Lambert conformal projection,” it was created in 1772 by the German-French physicist, philosopher, and mathematician Johann Heinrich Lambert (1728-1777). This is a shape-preserving conic projection, useful for topographic and meteorological maps, and particularly suitable for mid-latitude regions.
Gall-Peters projection
Created by Scottish clergyman James Gall (1808-1895) in 1855, this projection first appeared in the Scottish Geographical Magazine. It was popularized and implemented by German filmmaker Arno Peters (1916-2002) more than a hundred years later, in 1973, and for this reason it bears their names. This projection avoids the exaggeration of high-latitude areas, as occurs with the Mercator projection, but distorts shapes, stretches areas near the equator, and compresses areas near the poles.
Van der Grinten projection
Created in 1904 by the German-American cartographer Alphons J. van der Grinten (1852-1921), it presents the entire globe in a circle. It is neither conformal nor equivalent, but attempts to minimize distortions in shape, area, and distance across much of the map, although it exhibits significant variations in the polar regions.
Aitoff projection
Proposed in 1889 by the Russian cartographer David Aitoff (1854-1933), it is a zenithal or azimuthal projection that is not very equivalent and not very conformal, constructed by distorting the horizontal scale to turn the Earth’s sphere into an ellipse twice as wide as it is high.
Robinson projection
Created in 1963 by the American geographer Arthur H. Robinson (1915-2004), it emerged as a response to the mid-20th-century debate over a more accurate representation of the planet. Its purpose was to display the world map in a simple manner, so that it is neither equidistant, nor equivalent, nor conformal, but rather assumes its distortions (the most significant in the polar region and at high latitudes).
Winkel-Tripel projection
This is a modified azimuthal geographic projection proposed by Oscar Winkel in 1921, based on the combination of the Aitoff projection and an equidistant cylindrical projection. It was adopted by the National Geographic Society in 1998 and has since been considered the best model for terrestrial representation.
Please note: Although the Mercator projection is the most widely used for creating planispheres worldwide, it has received much criticism for being considered Eurocentric. This is because Europe is located above and in the middle of the image, the northern hemisphere appears dominantly in the upper plane, and the southern hemisphere is located in the lower plane, at the bottom of the image.
Why do cartographic projections exhibit distortions?
The Earth is a spheroid, meaning it has a curved shape in three dimensions. When attempting to represent this curved surface on a two-dimensional plane, such as a sheet of paper or a screen, the surface must be “unrolled” or “flattened.”
When converting a curved surface into a plane, geometric transformations are used that inevitably alter some geographic properties. The distortion phenomenon is inevitable in any type of projection. This is because it is impossible to faithfully convert a spherical surface into a flat one and preserve its distance, shape, and surface characteristics.
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References
All the information we offer is supported by authoritative and up-to-date bibliographic sources, which ensure reliable content in line with our editorial principles.
- Esri. (n.d.). About map projections. desktop.arcgis.com
- Garmendia, C. (2020). Map projections: what should I know?. Idecor. idecor.gob.ar
- National Geographic Institute. (n.d.). Cartographic projections. Educational Atlas. educativo.ign.es
- Mettatec. (2023). Cartographic projections and their types. mettatec.com
- Cartographic Projection Definition, Characteristics, Types, and Examples – concepto.de
