Geography

Cartographic projections


We know that the most appropriate way to represent the earth as a whole is by means of a globe.

But we need flat maps to study the surface of the planet. Turning a sphere into a flat area of ​​the map would be impossible if mapmakers did not use a mathematical technique called projection.

But imagine what it would be like if we opened a sphere and flattened it into a plane. Thus, the parts of the original sphere would have to be stretched, especially in the areas closest to the poles, creating large area deformations. So, to come up with the most accurate representation possible, cartographers developed various methods of cartographic projection, ie ways of representing a spherical body on a flat surface.

Since every projection results in deformations and inaccuracies, sometimes some characteristics must be distorted to correctly represent others. Deformations can occur in relation to distances, areas or angles. Depending on the projection system used, the largest alterations of representation are located in one or another part of the globe: in the polar, equatorial or mid-latitude regions. It is the cartographer who defines which projection will meet the objectives of the map.

The simplest and best known projection is that of Mercator (name of the Dutchman who created it). Other techniques have evolved and many other projections have attempted to undo the area inequalities near the poles with those near the equator, such as Gall's projection. Since there is no way to avoid deformation, each type of projection is classified according to the characteristic that remains correct. We have then:

  • Equidistant projections = correct distances
  • Conforming projections = equality of angles and shapes of continents
  • Equivalent projections = correctly show distance and proportion between areas

The following are the three main projection types.

They consist of the projection of parallels and meridians on a surrounding cylinder, which is later developed (planned). One of the most widely used cylindrical projections is that of Mercator, with a view of the planet centered on Europe.

It is the projection of the globe on a cone, which is later planned. They are most commonly used to represent the average latitudes, as only areas near the equator appear straight.

It is the projection of the earth's surface onto a plane from a certain point (point of view). Also called planar or zenithal, these projections deform areas distant from this central point of view. They are widely used to represent polar areas.