Map projections

Why no map is perfect

A sphere cannot be laid flat without tearing or stretching it, as the mathematician Carl Friedrich Gauss proved in 1827. A projection is a rule that takes each point on Earth (latitude and longitude) to a point on the map. It can keep angles right, so small shapes are faithful but areas are not; it can keep areas right, so shapes are stretched; or it can keep nothing exactly right but distort everything a little. Tissot’s indicatrices show this: they are identical circles on the Earth; on the map they change size where the projection changes areas and become ovals where it distorts angles.

Cylindrical, conic, azimuthal

Many projections come from a shape that touches the globe and is then unrolled. In cylindrical projections the sheet is a cylinder around the equator: parallels and meridians are straight lines, and distortion grows towards the poles (Mercator, Gall-Peters). In conic projections the sheet is a cone resting on a parallel: they work well for countries and continents at middle latitudes, such as Europe (Lambert). In azimuthal projections the sheet is a plane touching the Earth at one point: directions from the centre are right, and they are used for the poles or for distances from a place. Pseudocylindrical projections (Equal Earth, Robinson, Mollweide) have straight parallels but curved meridians, for an oval, less distorted Earth.

Mercator versus Peters

Mercator’s map (1569) was made for sailors: a course with the compass always at the same angle is a straight line. The price is that the farther from the equator, the bigger countries look: Greenland seems as large as Africa, which is in fact fourteen times larger. In 1973 the German historian Arno Peters presented a map that respected areas, accusing Mercator of making the countries of the global South look small. His projection was almost identical to one by the Scottish clergyman James Gall (1855), hence the name Gall-Peters; cartographers criticised it because it stretches shapes a lot, but the debate made everyone understand that a map is not neutral.

Equal Earth and the UN

Equal Earth was created in 2018 by Bojan Šavrič, Tom Patterson and Bernhard Jenny as an alternative to Gall-Peters: it keeps areas right but has the soft shape of the Robinson and distorts continents little. On 4 September 2026 the United Nations General Assembly adopted a resolution proposed by African countries that points to it as an option for representing the world more accurately (164 votes in favour, the United States against, six abstentions). It does not make it compulsory, but it is a strong signal against using Mercator for world maps.

How to choose a projection

It depends on what you want to show. To compare sizes and for thematic maps (population, GDP, climate) you need an equal-area projection, such as Equal Earth or Mollweide. For navigation or online maps, where you zoom down to streets, you need a conformal one, such as Mercator. For a country or a continent you choose a projection centred there, often conic. For distances from a place, an azimuthal equidistant projection centred on that place.