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Famous geographers: Gerardus Mercator

Gerardus MercatorBefore Gerardus Mercator came along, drawing a straight line on a map was harder than you might think. Read on to find out why.

Because the world is round and maps are flat, it is impossible for a map to show the world perfectly accurately. The map-maker has to decide which properties of the map to distort, such as distances or the shape of countries. A particular way of distorting the map is called a projection.

In 1569, Mercator, who had worked on a project to make a globe because of his skill engraving brass, invented a new projection with a very important property. On a Mercator map, a straight direction is represented by a straight line.

That might not sound very impressive, but the curve of the earth makes directions on maps more complicated. When you think you’re going in a straight line, you’re actually going in a curve. This means that, on many maps, you could keep going in a straight line but have to draw a curve on the map to show where you had been.

If you’re trying to sail across the world, it helps to be able to work out where you’ll end up if you set off in a particular direction. This made Mercator’s projection incredibly useful for explorers and navigators.

In fact, the Mercator projection is still used for navigation today. Among other places, it is used on Google Maps. However, most world atlases avoid it, because it distorts the size of countries, making places further from the equator look much larger than they are. But even in these, Mercator’s influence can still be seen: his book of maps was the first to be called an atlas.

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