Without a doubt, the most famous map projection is the Mercator projection. In fact, the Mercator projection was the first projection regularly identified in atlases. It is a cylindrical map projection that is a product of its time.

During the sixteenth century, new geographic information was pouring in from around the world, trade routes were being established, and sailors, explorers, and merchants needed accurate maps. After all, there's no profit or glory to be gained from getting lost or crashing your ship on a shoal.

Knowing this, Gerardus Mercator invented a new projection based on the cylinder. Mercator invented his map projection primarily for navigation. If you draw a straight line between two points on a map created using the Mercator projection, that line represents the direction you need to sail to travel between the two points. This type of route is called a rhumb line or loxodrome. It is not the shortest route, but if you keep the direction of your ship constant with respect to north then you will stay on course and arrive at your destination.

Note: The methodology behind the map was probably in use before Gerardus Mercator's time, but it was so obscure that it is believed to have been independently reinvented by Mercator in 1569.


Mercator projection


Because the Mercator map projection is cylindrical, and a cylinder is open-ended, the projection in theory goes on forever. This example has been "trimmed" before it reached 90 degrees north and south.


Because the Mercator map projection was the most commonly misused map projection during the nineteenth and twentieth centuries, many misconceptions have been propagated about the basic geography of the world. For example, Africa, the second largest continent, appears smaller than North America and Greenland. Also notice the extreme distortion at the polar regions. Some schools may still display wall maps based on the Mercator projection. You will learn more about the Mercator projection later in this session.


More about Gerardus Mercator

There are actually two cartographers named Mercator. The most prominent is Gerardus Mercator and the other is his son, Rumold, a prominent mapmaker in his own right.

Among cartographers and geographers, the name Gerardus Mercator is not simply well-known, but is uttered with reverence. As far as we know, he was the first person to apply the term atlas to a collection of maps in book form. (The book was actually published after Gerardus's death by his son.) It has also been said that Mercator saw a new form of lettering in Italy and introduced it to Northern Europe, naming it italics in honor of its place of origin. Although neither story can be substantiated absolutely, they help form the basis of a cartographic legend.


Gerardus Mercator


Gerardus Mercator.


Mercator's main claim to fame can be ascribed to two cartographic applications. He was the first cartographer to use latitude and longitude as an aid on sailors' maps. By applying a grid of intersecting lines (invented centuries earlier by the Greeks) to navigational maps, he paved the way for modern nautical charts.

His second contribution was a map that still bears his name—the Mercator projection, published in 1569. Mercator called his map A New and Enlarged Description of the Earth with Corrections for Use in Navigation. No wonder future cartographers and laymen simply called it the Mercator projection. This map revolutionized navigation because any line drawn between two points on a map is a sailor's compass setting that only needs to be adjusted to compensate for magnetic north. Because most navigators in the sixteenth century relied on their own personal and very secret maps, acceptance of the map projection wasn't immediate.



Drawing a line between two points on the map or chart shows a sailor the direction he needs to sail.


Gerard de Kremer (Mercator's real name) was born in Dumpelunde, Flanders (Belgium). His father was a merchant, believed to be a peddler or shoemaker. On March 5, 1530, Mercator attempted to make himself more acceptable to the gentry of the time by adopting the Latin name for merchant as his surname and Latinizing his first name. He attended the University of Levine, in Flanders, where he originally studied philosophy and later astronomy and mathematics. Upon completing his studies, he traveled extensively throughout Europe. When he returned to Levine he was arrested and spent seven months in jail for heresy. The charges were eventually dropped with help from his many colleagues.

He opened a cartography workshop in 1552 where he made earth globes, celestial globes, maps, atlases, and instruments for sailors and the wealthy. He made the first map of Flanders and of the British Isles and completed his masterpiece, Mercator's Great Atlas.

Gerardus Mercator died on December 2, 1594, in Duisburg, in what is now Germany. (Snyder 1987, 1993, and Tooley 1987)


Transverse Mercator

The Transverse Mercator map projection was invented by Johann Lambert and presented in 1772. Lambert rotated the Mercator cylindrical projection 90 degrees, making the tangent line a line of longitude instead of the equator.

Only the central meridian and the equator of the projection are straight lines. All other latitude lines and longitude lines are complex curves; that is, they cannot be represented as sections of a single circle. Unlike the Mercator projection, the Transverse Mercator projection is not used on a global scale but is applied to regions that have a general north–south orientation.


Transverse Mercator


Feature distortion increases proportionally as the distance from the central meridian (the red vertical line) increases. For this reason, the Transverse Mercator map projection is applied to regions with a north-south orientation.


Although it isn't used (and can't be) to project the whole world in a single map, the Transverse Mercator is used to map the whole world in pieces—more exactly, in a series of adjacent strips. That's the idea behind the Universal Transverse Mercator coordinate system, which you'll learn about in the next session.