Map(s) of the Month: Global Map Projections

Map projections have been in the news lately: representatives of the African Union and advocacy groups are calling for a replacement of the Mercator projection (used frequently online, like in Google Maps) with the Equal Earth map. But you may well wonder: what is a map projection? How could it matter?

Map projections are ways of depicting the three-dimensional surface of the earth as two-dimensional maps, and they matter because there is no way to do this without distorting some aspect of the map. For example, if you imagine a map of the whole earth, you might well imagine it in the Mercator projection (like this 1948 world map). It was designed in the sixteenth century for maritime navigation, so it preserves direction but distorts area. On this map, Greenland looks huge, but in reality, it is only one-fourteenth the size of Africa.

As one alternative, consider this 1950 world map in Goode's Homolosine equal-area projection (also shown above). It accurately depicts area, so Africa and Greenland are their proper sizes, but it introduces interruptions in the map. (Similarly, have you ever wondered what a globe looks like when flattened? See our 1942 globe gores for an example.)

At this point, you might wonder about other cartographic conventions: 

• Why do we center world maps on the equator? (You don't have to! See this 1944 map centered on the North Pole, showing flight distances between major cities.)
• Why is North up? ("Up" was East on some medieval European maps, and South on some maps from the Islamic world.) We recommend this book for the curious: Why North is up : map conventions and where they came from.

Since maps always distort, and since there are many historical ways that maps can and do depict the world, now you can understand why the Mercator projection diminishes the size - and perhaps the perceived importance - of Africa, South America, and other regions in the Global South.

For a humorous yet informative take on this longstanding issue, enjoy this famous clip from the West Wing. And for more cartographic comedy, see the webcomic XKCD's series on bad map projections.