The Different Cartographic Projections and What They Mean
The Different Cartographic Projections and What They Mean
Cartography consists of the flat, simplified and conventional geometric representation of the earth’s surface, presented in the form of maps, charts or blueprints. Because it is a two-dimensional representation of something that is three-dimensional, all representations undergo some kind of deformation, so that the choice of a method takes into account not only technical aspects, but also political ones.
Although the cartography is attributed to the Sumerians, there are earlier records of cave paintings and even stone carvings made by Eskimos and Aztecs, which suggest attempts to represent small localities. All great civilizations used drawings and models as communication tools. The Egyptians, for example, used it as an administrative tool, to collect taxes and demarcate the land, while the Greeks are considered the “fathers” of contemporary cartography, uniting their varied knowledge of the fields of geometry and astronomy.
The development of cartography reached the maps of maritime routes, which combined technical data with ethnographic interpretations of the routes, bringing the anguish of the unknown from the portrait of the challenges of the journey, illustrated by sea monsters, storms, etc. David Harvey states that “from an ethnocentric perspective, the voyages of discovery produced an astonishing flow of knowledge about a larger world that had to be somehow absorbed and represented. They indicated a globe that was finite and potentially apprehensible.”
In this way, from the exploration of the seas and the expansion of knowledge about the land, maps gain a more technical and informative character, reaching what we have today in contemporary cartography, based on projections. These transform a three-dimensional element, the planet Earth, into a two-dimensional drawing, a map. This kind of “translation” makes a perfect projection impossible, and therefore, all representations have some deformation. This deformation is related to the tangency area, which is the point where the projection comes into contact with the surface of the globe. The regions closer to this axis can be portrayed more closely to the real thing, and the distortion increases in the opposite direction of the area.
Cartography recognizes three types of projection, the cylindrical, which uses a cylinder as the area of the plane; the conic, which uses a cone as a plane; and the plane or azimuthal, which does not have a specific plane or tangency area, but normally uses the poles as centrality. In addition to projection types, another important criterion for representations is their property, according to the areas, angles or distances of the representation. The representation must be faithful to one of these criteria, but for geometric reasons it cannot respond to all three at the same time. Among the many variations and multiple criteria, maps can be classified by combining their type of projection with their property, such as the Mercator Projection, which is a cylindrical projection with its main axis in the northern hemisphere, valuing in size the countries of that part of the globe, without changing the angles at any point of the projection.
Another important projection is the Peters projection, which is also cylindrical, but instead of the Eurocentric highlight, it preserves the real areas and ends up highlighting the countries of the southern hemisphere. Currently, the most commonly used representation is the Robinson projection, an aphylactic representation, which does not preserve any properties such as area, distance or angle, and which is also pseudocylindrical. The intention of this projection is to reduce the angular distortions, which generates a minimum distortion of the continental areas, being, therefore, considered the projection that best presents the land masses.
Assuming that cartography is not an absolute representation, but an attempt to illustrate reality, Adriana Lopes Rodrigues states that “while projection seeks to be a mathematical ratio of proportions for the transposition of what is in the physical world to a plane on paper, distortion would be a reminder that something was left out. Both terms, projection – as transference – and distortion – as equivocation – reaffirm that the map needs to be interpreted, it depends on an attentive reading of its production conditions”. Thus, all representations need to be critically read. An example of this is the area ratio between the area of the Sahara Desert, which is close to 9 thousand km2, but on the map it is usually portrayed as smaller than some countries, such as Brazil, which has a territory of about 8 thousand km2.
Today’s technology allows for more realistic views and more reliable data from reading the territory of the earth’s surface. However, as with older projections, the data collected need to be read, analyzed and critically interpreted so that they can serve as a basis for scientific knowledge.