The great map debate

Under the microscope Cartography can be highly controversial, particularly when it pinpoints global warming contributors or the death tolls in forgotten wars.

In 1973, a German amateur historian sparked a storm of controversy by claiming to have invented a whole new way of looking at the world. At a press conference at the United Nations in New York, Arno Peters condemned the standard rectangular map of the world as a symbol of the subjugation of the Third World. The time had come, said Peters, for a new type of map - one that properly represented the Third World.

Cartographers had always known about the flaws of the rectangular map. Based on the method for displaying the Earth's surface known as Mercator's projection, it notoriously squashes regions near the equator while expanding those in high latitudes. But Peters declared that the resulting distortion "overvalues the white man and distorts the picture of the world to the advantage of the colonial masters of the time".

Peters then unveiled his own solution: a new way of projecting the world's nations that maintains their relative areas. The result, known as the Peters Projection, is certainly striking: Africa and South America appear to dominate the planet, while Europe and America seem much smaller, and Greenland - which dominates the polar regions of the rectangular map - almost vanishes from sight. By the time of his death in 2002, Peters had persuaded many official organisations to take up his projection, among them Unesco and Unicef. Yet to this day his name and claims provoke ire among many professional cartographers. They point out that the idea of area-preserving projections was invented more than a century before Peters, by a Scottish cartographer named James Gall, and that it too has its flaws - not least that the shape of the nations are distorted, and the map is much harder to use for navigation.

But for many cartographers, it's the very idea of one map being more "politically correct" than all others that rankles most. One can therefore only applaud the courage of the international team led by Professor Danny Dorling of the University of Sheffield, UK, who has come up with not just one but a whole atlas of politically explosive maps. They are the founders of the Worldmapper project, whose aim is to build up a collection of so-called "cartograms": depictions of the world with nations resized according to characteristics such as population or religious affiliation. So far, the team has created almost 600 maps, many of which are featured in The Real World Atlas, published this month by Thames and Hudson, and also on the project website at www.worldmapper.org. As with the map based on the Peters Projection (or, as cartographers prefer to call it, the Gall-Peters Projection), the results have a striking ability to change one's perceptions of the world. For example, map 299, showing greenhouse gas emissions of nations in 2002, leaves no doubt about who is contributing the most to global warming, while map 288, showing war deaths in 2002, serves as a stark reminder of the forgotten wars of Africa. The creation of these maps represents a major achievement in the ancient art-cum-science of cartography, whose immediately accessible results so often belie mind-boggling complexities. The most basic of these is the problem of portraying the curved surface of the Earth on a flat sheet of paper. Early cartographers knew this was hard to do without introducing some distortion (surprisingly, it took until 1827 for its impossibility to be proved with mathematical rigour). Instead, mapmakers came up with various projections, each with its own set of faults and compromises. The most famous emerged in 1569, when the Flemish cartographer Gerard Mercator imagined wrapping a sheet of paper around the Earth's equator in a cylinder, and projecting on to it every point on the globe via imaginary "rays" emerging from the Earth's centre. The result distorts the relative sizes of countries, especially those in high latitudes like Greenland. But Mercator's projection has one huge advantage: courses that look like straight lines on the map are really straight lines. Over the years, more than 200 other projections have emerged, from the simplicity of the Hammer Equal Area method, whose oval-shaped image of the world adorns many corporate logos, to the complexity of Mollweide's Interrupted Homolographic, which captures the surface of the Earth on a kind of flattened orange peel. The cartograms in the Real World Atlas represent the latest breakthrough in attempts to make maps work harder. Cartographers have long sought ways to create maps whose appearance reflects key features of different regions. And in principle, it seems simple enough: just scale up the area of each nation according to its share of the global total for that characteristic. But the resulting change in shape stops the regions from fitting together properly, making the resulting map hard to understand. Research by members of the Worldmapper Project, including Professor Dorling and Dr Mark Newman of the University of Michigan, has now resulted in methods of solving this tricky jigsaw puzzle. When run on a computer, the result is a whole new family of maps - and an atlas which may well put cartography back on the political map. Robert Matthews is a Visiting Reader in Science at Aston University, Birmingham, England www.robertmatthews.org