Map Projections

Map Projections Help ‘Flatten’ Our World

September 18, 2018


Imagine if there were no maps at all, and we had to rely only on globes to determine locations and distances. It wouldn’t work very well. Maps are easier than globes to transport and store, of course, but there’s more to their superiority than that.

Maps can be produced at any scale, which means they can include massive parts of the Earth's surface. Or, maps can illustrate the tiniest portion of our world, in minute detail. They make it easy to measure land areas, are less expensive than globes to produce, and meld perfectly with modern digital technology.

With such clear benefits, the creation of maps, and the development of map projections, has been a valuable endeavor for centuries.

When you try to take an image that’s stretched over a sphere and flatten it out, the image becomes distorted. That’s where map projections come in. Wikipedia defines a map projection as “a systematic transformation of the latitudes and longitudes of locations from the surface of a sphere or an ellipsoid into locations on a plane.” Unfortunately, there’s no way to execute that “transformation” without distorting the image. People who create map projections are in the business of minimizing that distortion.

Depending on what the map needs to illustrate, certain distortions can be allowed. It’s all about deciding which properties of the source globe need to be represented accurately in the map. Some map projection types have become more popular than others. The rest of this article contain a brief overview of three very common map projection types: cylindrical, conic, and azimuthal.

Cylindrical Map Projections.

This is what you probably think of when you think of a map. A cylindrical projection is “any projection in which meridians are mapped to equally spaced vertical lines and circles of latitude (parallels) are mapped to horizontal lines.”

When laid out, a cylindrical map is rectangular; the term “cylindrical” refers to the fact that they can be rolled into a tube, or cylinder. Cylindrical map projections enable a high degree of scale accuracy in smaller areas.

There’s one catch though—cylindrical map projections distort the poles. When compared to actual Earth geography, equatorial regions will be represented with a high accuracy, but a map of this type can’t allow for the curvature of the Earth, so the properties of the north and south pole will be less accurately illustrated. Cylindrical projection
Figure 1: Example of cylindrical projection.

The most famous cylindrical map projection is the Mercator, created in 1569 by a Flemish cartographer and geographer, Geradus Mercator. With all the parallels of latitude having the same length as the equator, cylindrical map projections like the Mercator are used extensively for marine charts.

Conic Map Projections

A conic map typically features two arbitrarily selected standard parallels that represent lines where the cone intersects the globe. Near those standard parallels, conic maps limit distortion drastically, presenting scale, shape, and area more accurately.

One extremely common conic map projection is the Lambert Conformal Conic projection.

Lambert prction
Figure 2. Example of conic projection

Representing meridians as straight lines and parallels as circles, conic map projections are commonly used to create regional or hemispheric maps. The specific distortion inherent in conic maps makes it less than ideal when visualizing the whole planet, but regional weather and climate maps work well using conic map projection.

Azimuthal Map Projections

An azimuth is the horizontal angle or direction of a compass bearing. An azimuthal projection plots the surface of Earth using a flat plane. The directions are correct from the center of the map to any other point, with circles through the center projected to straight lines on the plane.

Cylindrical projection
Figure 3. Example of Azimuthal projection

Azimuthal maps are great if you need to find direction from any place in the world, using the central point as a reference.

Map Projection—a Practice in Specialization

All map projections distort, so it’s hard to say which type is the most useful, but cylindrical map projections have proven to be one of the best types in accurately representing scale over smaller areas. Numerous map projection types have been developed, and new ones are still being created. Map projection always comes down to the specialized goals of the cartographer. It’s all about which properties of the mapped area need to be represented with the highest degree of accuracy.

Learn more about different map projections in this YouTube video from SciSchow!