MAPS of the world have the impossible task of portraying the Earth—a three-dimensional shape—on a flat sheet of paper. Mapmakers have to choose a projection of the globe that approximates the basic properties of shape, size, direction, distance and scale. Of the many projections available, none is perfect. All of them distort some aspect of the globe in the necessary trade-off between these properties. That can give a misleading, and some would say biased, view of the world. How?

Online maps provided by Google, Microsoft and others use the Mercator projection to display the world. In doing so they perpetuate huge distortions in how the Earth is seen. The 16th-century cylindrical projection by Gerardus Mercator, a Flemish cartographer, makes life easier for navigators by keeping parallels and meridians as straight lines. But in doing so it distorts the world in a way that misrepresents countries’ shape and size to a degree that increases the farther away they are from the Equator. This results in Africa, which sits across the equator, appearing smaller than high-latitude Greenland when it is in fact 14 times larger. The “Greenland problem” has long been recognised, even outside professional cartographic circles.

One of the Mercator projection’s fiercest critics was Arno Peters, a German historian. He reckoned that the widespread use of Mercator out of the thousands of projections available was a sign of bias. In Peters’ view, the Mercator projection was preferred because it exaggerates the size of northern European countries to make them appear more powerful when set against their conquests in the southern hemisphere. His solution, a modified projection known as the Galls-Peters projection, preserves area. This approach displays the size of countries accurately but still distorts their shapes, and has failed to become widely adopted (see our map "slider" above for a comparison of the two projections). For online mappers such as Google, the ability to zoom in and out of the globe, while maintaining North at the top of any view, requires a projection with vertical lines of longitude. The distortions are negligible when viewing small parts of the globe with Mercator’s projection and generations have grown up viewing the projection in atlases and wall maps at school. The benefits of its rectangular shape, simplicity and familiarity are hard to beat.

But there is no such thing as a perfectly accurate map. All maps distort reality and convey bias (whether deliberately or not). With modern mapmaking software, choosing a different and perhaps more appropriate projection, depending on the area to be displayed, should be much easier. Perhaps the time has come to abandon the universal reliance on the Mercator projection in favour of maps that offer a better compromise on the true shapes and sizes of the various countries of the world.

Dig deeper:

How Google represents disputed borders between countries (Sept 2014)

Geography matters as much as ever, despite the digital revolution (Oct 2012)

The true true size of Africa (Nov 2010)

