La projection de Mercator : Comprendre son impact et ses implications en cartographie

The Mercator projection: Understanding its impact and implications in cartography

The Mercator projection is much more than a simple method of cartographic representation: it is the reflection of an era, a necessity and a genius. Created by the Flemish geographer Gerardus Mercator in 1569, this projection has become essential in the spheres of navigation and cartography. Let's discover this process, its fascinating history, its undeniable advantages, but also the controversies it has generated.

Origins of the Mercator projection

The Renaissance, a period teeming with discoveries and innovations, changed our view of the world in many ways. Among the emblematic figures of this era, Gerardus Mercator stands out for his revolutionary contribution to cartography.
Born in 1512 in a region that is now part of Belgium, Mercator showed a keen interest in geography, astronomy, and mathematics early on. Trained at various European universities, he quickly built a reputation as a cartographer and instrumentalist. However, what made him unique was his ability to perceive the practical challenges of the navigators of his time and to provide innovative solutions to them.
Before returning to its famous projection, let's take a look at two crucial principles in navigation: orthodromy and rhumb line. Great circle refers to the shortest path between two points on the surface of a sphere, often represented by a curve on a map. In contrast, the rhumb line is a path that crosses all meridians at a constant angle, meaning that a ship following this course would maintain a constant heading. For 16th-century sailors, sailing on a constant course was essential, as it greatly simplified navigation by avoiding constant recalculations.
The main idea of ​​the Mercator projection was therefore to offer a representation where the rhumb lines appeared as straight lines. To achieve this, he designed a conformal projection, that is to say it preserves the angles. While this makes constant heading navigation much more intuitive, it also comes at a cost: the projection is not equivalent, meaning it does not preserve surface proportions.
Mercator projection
Mercator projection

The undeniable advantages of the Mercator projection

The Mercator projection, despite its controversies, has a series of advantages that have made it one of the favorite tools of navigation and geography professionals since its creation. Here's why it has remained so popular throughout the centuries.

Linear representation of directions

One of the most attractive aspects of the Mercator projection is its ability to render directions as straight lines. This deceptively simple feature solves a major challenge for browsers. Indeed, on the high seas, without clear visual landmarks, having a map where a route to follow is represented by a simple straight line is invaluable. This eliminates guesswork and allows for more precise and direct navigation.

A universal tool for professionals

Beyond sailors, other experts benefit from the Mercator projection. Cartographers, for example, appreciate its linear representation to draw or redraw routes and regions. Geographers, for their part, benefit from its clarity when it comes to analyzing spatial relationships between different regions of the world.

A global vision on a single surface

In the world of cartography, synthesizing information without losing precision is a true art. The Mercator projection excels in this. Whether large atlases or global maps intended for the general public, its ability to condense the immensity of our planet onto a single flat surface is impressive. This compactness makes reading and interpreting the map more accessible, thus facilitating the understanding of global dynamics.

Flexibility and adaptability

The Mercator projection adapts as well to global representations as to more specific regions, such as oceans or continents. This flexibility allows it to meet the varied needs of users, whether they are navigators seeking to cross an ocean or researchers analyzing phenomena on a regional scale.

The limits and controversies surrounding the Mercator projection

The Mercator projection, while a wonderful achievement in the field of cartography, is not free from criticism. Although recognized for its practical advantages, it has raised, and still raises, passionate debates around its broader implications, both geographically and socio-politically.

Perceptible deformations

The main criticism of the Mercator projection is its tendency to exaggerate the size of land as we move away from the equator. This is a direct consequence of its initial objective: to render directions in the form of straight lines. Thus, Greenland, to take a striking example, appears comparable in size to Africa, when in reality it is 14 times smaller!

Sociopolitical implications

Beyond geographic distortions, the way the Mercator projection represents the world has sociopolitical implications. By disproportionately enlarging regions far from the equator, it minimizes, through a mirror effect, the visual importance of the equatorial regions where many developing countries are located. This depiction has been criticized as Eurocentric, reinforcing, even if unintentionally, a Western-dominated worldview.

A distorted vision of our planet

If the distortions of the Mercator projection were simply aesthetic, they could be more easily dismissed. However, the way we view the world influences our understanding of global issues. The inaccuracy of proportions can influence our perception of the seriousness of certain problems, such as the territorial power of Russia or the issues linked to deforestation in equatorial countries.

Alternatives to Mercator

Faced with criticism, many alternatives to the Mercator projection have emerged. Projections like Gall-Peters' seek to offer a more balanced and less distorted view of the world. However, it is important to remember that no projection is perfect, and each has its own advantages and disadvantages.
Gall-Peters projection
Gall-Peters projection


By painting the picture of the Mercator projection, we discover a revolutionary technique, which was able to meet the needs of the explorers of its time. However, like any tool, it has its imperfections and gives rise to debate. But, undeniably, Mercator's contribution to cartography and navigation is colossal, and his legacy is still felt in our current representations of the world. As we look through today's maps, let's take a moment to appreciate the ingenuity and genius of those who charted the contours of our understanding of the world.
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