Map Projections


WORLD MAP PROJECTIONS

Transferring the earth's features onto a flat map using a grid composed of lines of longitude and latitude.

It may come as a surprise to learn that nearly every world map which you have ever seen will not have represented countries in their correct, proportional size to one another. Indeed, only a globe has the ability to illustrate the earth’s characteristics precisely.

The transference of the features of the earth’s surface onto a flat surface has been subject to interpretation and choice since the earliest days of world mapping; here, you can read a little bit about the history surrounding map projections.

As a way of introducing the issues which surround world map projections, why not take a look at the clip in the bottom left corner of the page from the popular NBC television series West Wing?



Mercator

New Mercator

For much of the twentieth century the world was portrayed by the Mercator projection, originally produced in 1569 for navigational purposes by Gerardus Mercator.

In order to represent the world as flat, the Mercator projection treats the world as a cylinder, essentially keeping the lines of latitude parallel to one another, instead of converging at the poles. In an attempt to regain accuracy of shape (a very important quality for a navigational map), the lines of latitude, of equal distance from one another on a globe, were stretched as their distance from the equator increased.

This method might have regained accuracy in shape, but the stretching hugely distorted the area of countries, especially those closest to the poles.

The Soviet Union became 223% bigger than it really is, Greenland 554%, Canada 258% and the United States 68%.


  

Cylindrical Equal Area

new equal area

The cylindrical equal-area projection sacrifices the accurate shapes of Mercator’s projection to represent countries in their correct proportional size.

This is done by narrowing the lines of latitude as they approach the poles, in order to compensate for the missing convergence of the lines of longitude.

The map is a very different vision of our planet, one which gives emphasis to different areas of the world. Although as extreme in its portrayal of the world as Mercator’s projection, it highlights the deficiencies of that projection as a geographical teaching aid.

The cylindrical equal-area projection was first brought to the public’s attention in the 1970s, by the German historian Arno Peters. He marketed his version of Gall’s orthographic projection, first published in 1855, to great success.

The Peters projection has had over sixteen million copies distributed in six languages.

The cartographic industry was well aware, of course, of both of these projections’ failings as geographical maps; in 1989, the American Cartographic Association issued a resolution, urging publishers and agencies ‘to cease using rectangular (cylindrical) world maps for general purposes or artistic displays’.

In doing so, the two most high-profile map projections of the twentieth century began to make way for a series of pseudo-cylindrical projections (commonly having parallel lines of latitude and curved meridians), first experimented with in the 1800s.

Robinson

New Robinson

In 1963, map publisher Rand McNally asked Arthur H. Robinson to select a world map projection that fulfilled a list of nine requirements, including the area-scale distortion described above.

Arthur Robinson could not find a suitable existing projection and so set about designing a new one. Rather than using the traditional method of computing co-ordinates by mathematical formulae, he used a more visual trial-and-error development.

“I started with a kind of artistic approach,” Dr Robinson said in a 1988 interview with The New York Times. “I visualised the best-looking shapes and sizes. I worked with the variables, until it got to the point where, if I changed one of them, it didn’t get any better.”

Only then did he “figure out the mathematical formula to produce that effect”. For his projection Dr Robinson chose 38 degrees north and 38 degrees south as the standard parallels. This established the two places on the map where both size and shape are the most accurate, in the middle of the temperate zone, where most of the land and people are found.

The projection was used immediately in various atlases which Rand McNally produced and as a wall map as well. However, purchasers had become so used to the visual of the Mercator projection that sales were not as expected, and the sheet map was withdrawn from popular distribution.

It wasn’t until 1988, when The National Geographic Society was looking for a projection to replace the Van der Grinten one it had used since 1922, that the Robinson Projection got its full and deserved push into the public eye.