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What is a Mercator Map?

A Mercator Map is a navigational tool that has guided explorers for centuries. It projects the earth onto a flat surface, distorting size but keeping angles intact, ideal for plotting straight-line courses. However, its design skews our perception of landmasses, especially near the poles. How does this affect our understanding of geography? Join us as we explore the implications of this cartographic staple.
Archana Khambekar
Archana Khambekar

Maps of relatively small regions of the Earth such as a state or a province accurately show places, distances, and directions. For larger regions of the Earth such as a hemisphere, or, for the whole Earth, a map cannot show all distances and directions accurately because the Earth is round, whereas maps are flat. Depending on the intended use of the map, different mapping techniques have been invented to show some aspects such as distances realistically at the expense of other aspects such as direction or the relative size of land masses and bodies of water. A Mercator map is a technique where compass directions are shown as straight lines. It helped sailors map routes to distant places and became the standard for world navigation.

A cylinder can be cut and smoothly rolled out into the flat surface of a map. Due to this property, different globe-to-cylinder mappings have been invented by people over the past centuries. In a simple mapping method, one wraps a transparent sheet of paper into a cylinder around the equator of a globe. Then while keeping the North Pole of the globe pointing straight up, one can view all points of the globe horizontally, and mark them on the paper.

A Mercator map translates the globe onto a flat map.
A Mercator map translates the globe onto a flat map.

In this mapping, longitudes are represented as equidistant vertical lines, and latitudes as horizontal lines. East-west distances are accurate at the equator, but expand everywhere else. For example, Greenland looks enormously wide. In fact, the North and South poles are stretched out along the length of the map even though they really are mere points. This is true for all cylindrical mappings where the cylinder connects to the equator of the globe.

In the mapping described above, north-south distances are accurately represented. As east-west distances vary from the equator to the poles whereas north-south distances do not, such a map causes difficulty while traveling to distant places because the route one should take is not always shown as a straight line. In 1569, Flemish geographer and cartographer Gerardus Mercator invented the Mercator map where the routes of any given compass direction where shown as straight lines. The Mercator map was considered a significant invention as it came at a time when shipping and nautical navigation was gaining importance.

Mercator stretched north-south distances to match the east-west stretch at any given latitude. This made the distances, and hence the scale, identical in all directions around any point. Nevertheless, areas away from the equator, such as Greenland, looked huge because they were vastly wide and vastly tall. In spite of this, Mercator’s method of mapping was very useful to sailors.

A Mercator map is useful in depicting the regions from the equator to the area about the Arctic and Antarctic circles. Beyond that, the distortion in distances and areas is extremely large. Nowadays, airplanes are able to follow shortest routes across the globe; however, such routes do not utilize constant compass directions, but constantly curving routes called "great circles." Still, a Mercator map is very popular for showing areas and countries near the equator. Mercator maps are often used by established online map software as the calculations for zooming in and out can be done speedily.

Frequently Asked Questions

What is a Mercator Map and why is it significant?

A Mercator Map is a type of map projection created by Gerardus Mercator in 1569. It's significant because it represents a navigational breakthrough; it allows for straight-line sailing courses to appear as straight lines on the map, which was invaluable for European explorers. However, it distorts size and distance as it moves away from the equator, making landmasses like Greenland and Africa appear inaccurately large or small, respectively.

How does the Mercator Map distort the size of continents?

The Mercator Map distorts the size of continents due to its cylindrical projection method. As it projects the globe onto a flat surface, it stretches the poles horizontally. This means that the further away from the equator, the more pronounced the distortion. For example, Greenland appears roughly the same size as Africa on a Mercator Map, whereas in reality, Africa is about 14 times larger, according to the National Geographic Society.

What are the advantages of using a Mercator Map?

The primary advantage of using a Mercator Map is its utility in navigation. Because it preserves angles, a navigator can plot a straight-line course known as a rhumb line, which is a constant compass bearing, making it easier to navigate between two points. This feature made the Mercator Map the standard for nautical charts. Additionally, its rectangular grid is easy to use and familiar to many, aiding in its widespread adoption.

Are there alternatives to the Mercator Map that provide a more accurate representation of the world?

Yes, there are several alternatives to the Mercator Map that provide a more accurate representation of the world. The Gall-Peters projection is one such example, which presents landmasses in their actual size relative to each other, although it distorts shape. The Winkel Tripel projection, recommended by the National Geographic Society, balances size and shape distortion, making it a popular choice for world maps. The Robinson projection is another alternative that creates a more visually appealing balance between size and shape distortions.

Why do schools and educational institutions still use Mercator Maps?

Schools and educational institutions often use Mercator Maps due to their historical significance and navigational utility. They are also widely available and familiar to many educators and students. However, there is a growing movement in education to introduce a variety of map projections, including those that more accurately depict the size and shape of continents, to provide a more comprehensive understanding of geography and the limitations of different map types.

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    • A Mercator map translates the globe onto a flat map.
      By: Marco Forante
      A Mercator map translates the globe onto a flat map.