The Mercator Projection is the most recognized map of the world today. Developed by Flemish cartographer Gerardus Mercator in 1569, it revolutionized sea navigation. It quickly became the de facto view of the world, propogated into classrooms all over the world and even used by Google as late as 2018. Unfortunately, this is a case of wrong tool for the job.
What is a projection? A projection is a two-dimensional representation of the surface of a globe (in this case, the earth). All projections are distortions – the 2D projection makes it impossible to preserve both the angles and the area of a 3D object. This was the topic of mathematician Carl Gauss’s Theorema Egregium, which is probably best expressed in layman’s terms as: a globe contains curvature and a piece of paper does not, and therein lies the rub.
Back to the Mercator Projection. Mercator conceptually represented the globe as a cylinder, cut the cylinder and then spread it out onto a piece of paper. This allowed him to represent longitude as parallel lines (when, on a globe they converge at the poles). Designed specifically for sea navigation, parallel longitudes allowed for direct rhumb lines from point A to point B, so ships could maintain the same relative course for an entire trip. The compromise was that to keep the longitudes parallel, Mercator had to stretch the latitudes farther and farther as you move away from the equator.
Now about those gross inaccuracies. Since the distances between degrees of latitude get larger as you get farther away from the equator, the size of land masses are equally distorted. The most obvious example is Greenland. Yes, Greenland is big (the 12th biggest country in the world by land mass) but in the Mercator projection it appears the same size as the continent of Africa. Another good example is Alaska. Again, legitimately huge (bigger than the next three largest states combined) but in the Mercator projection it appears to be the size of half of the United States. The problem was exacerbated when map makers, apparently bothered by the ‘infinite’ representation of Antarctica, removed Anartica from the map. That moved the equator downward from the middle of the map and further emphasized the enlarged northern hemisphere. Here is the Mercator projection with the actual size of land masses also represented:
Intentional bias? When mapmakers removed Antarctica for aesthetic reasons, it pushed most of the skew to the northern hemisphere, having the effect of enlarging all of North America, Europe and Russia and also putting them more centralized on the map. Unintentional or not, this causes a map bias¹ towards the traditional industrialized nations. In recent years this has led some school districts to reconsider which projection to display in classrooms. But, as all projections are flawed in some way, this has also led to controversies.
What should we, as intelligent consumers, do? Take a page from Supreme Court Justice Potter Steward – “I’ll know it when I see it.” If you see a map of the world with an engorged Greenland, know that it is a Mercator Projection, that it was designed specifically for sea navigation, and that it doesn’t accurately reflect the size of land masses. And if Antarctica is chopped off, know that the equator isn’t in the middle of the picture, making the situation even worse.
In the case of projections, not only isn’t there a one correct answer, there isn’t even a good least incorrect answer. Like much of life, the best solution is to be aware of the limitations.
¹ Map bias refers to the tendency for our eyes to focus primarily on larger regions on a map, and less on smaller ones.
