Gerardus Mercatorís (1512-94) projection is important to geographers because, unlike other projections, a straight line drawn on it gives a true compass bearing.
A projection is simply a means of transferring a round section of the world on to a flat sheet of paper. This is more easily said than done, for, no matter how hard you try, you cannot do it without altering the shapes or sizes of countries or the distances between them.
You can try this for yourself. Draw a rough map of the world on an orange with a felt tip pen, then cut the orange into sections. When you have eaten the orange, try to arrange the curved pieces of peel into a flat map.
You can see that if the lands by the Equator, or the widest parts of the orange peel, are touching, there are large gaps to the north and south. To make a map in which there are no gaps, it is necessary to stretch these lands in the north and southóand this is just what Mercator did.
The history of projections goes back to the Greeks who realized as long ago as 500 B.C. that the world was round. Eratosthenes, a Greek who lived at Alexandria in the 2nd Century B.C. even calculated the circumference of the world to be 25,000 miles. His estimate was only a little more than the correct distance which is 24,901.8 miles at the Equator.
Mercatorís projection increases the distances between the lines of latitude (the lines parallel to the Equator) as one moves further north or south. While this makes the map useful for navigation, it also gives people many wrong ideas about the world.
It makes some countries, such as Greenland appear too large. The areas of land at the Equator on Mercatorís projection are correct. But those at 45 degree North or South are doubled, and those at 75 degree are nearly 16 times too large.