Let's have a look at what a map projection is, how it works, and the main pros and cons of some of the most commonly used projections.
The new Advanced World map on MapChart lets you choose from nine different projections for making your map.
This is a really useful feature (among others available) that can completely change the design and feel of your map.
In this post, we will quickly go over what a map projection is, how to classify the various map projections, and the advantages and disadvantages of some of the most popular ones, including those available on MapChart.
What is a map projection?
The surface of the earth is curved but maps are flat.
A map projection is a method by which we translate a sphere or globe into a two-dimensional representation.
In fact, the term “map projection” comes from the concept of projecting a light source through the earth’s surface onto a two-dimensional surface (a map).
Map projections are essentially ways to represent a three-dimensional world as a flat surface, usually a screen or paper.
Types of map projections by surface
Map projections are created using mathematical formulas. As a process, we use a surface to wrap around the earth and project the latitudes and longitudes to corresponding geographical coordinates on a map.
There are three main types of surfaces that a map can be projected onto: a plane, a cone, and a cylinder.
The surfaces can then be laid flat and produce a representation of the Earth’s surface as a map.
Each of these types provides accuracy for some features while distorting others.
If we use a flat plane to plot the surface of the earth we get azimuthal projections, which are more accurate for Polar regions.
If we place a cone on the Earth and unwrap it, this results in a conic projection. These projections are best for mapping long east-west regions because distortion is constant along common parallels.
Finally, a cylinder wrapped around the earth so that it touches the equator will produce a cylindrical projection. The resulting tends to be more accurate around the equator.
Variations to the 3 main categories produce even more types, like pseudocylindrical, modified azimuthal, pseudoconic, hybrid, etc.
Types of map projections by preserved property (area, shape, direction, distance)
Projections are atrade between distortion, accuracy, and aesthetics.
Some map projections maintain areas, while others preserve local shapes, distances, and directions.
No projection, however, can preserve all attributes.
Depending on which metric property the projection preserves, we can classify them as follows:
- Conformal: preserving local topography, ie. the shape of features. Examples include Mercator, Lambert Conformal Conic.
- Equal-area: preserving area measure, mostly distorting shapes in order to do that. Some examples are Eckert IV, Sinusoidal and Mollweide projections.
- Equidistant: preserving distance between two points. Example is the Plate carrée projection.
- Compromise: these provide a representation of the earth that is not perfectly correct in any way but not badly distorted in any way either. Notable ones are Winkel Tripel, Miller cylindrical, Robinson, van der Grinten, etc.
As a rule of thumb, compromise projections should usually be your choice for maps of the entire world, like the ones that you can create on MapChart. They benefit from getting close enough to the real proportions and shapes, while also being aesthetically pleasing.
Map Projections on MapChart
There arethousands of map projectionsin existence today.
Let’s take a look at some of the most popular ones, that are also available on MapChart.
For the below map projections, we will be listing some of their main characteristics, as well as their pros and cons. At the end, we will provide some suggestions on how to choose the right map projection.
It can be helpful to have open at the same time the Advanced World map on MapChart, where you can see all these projections in action and quickly switch between them to get a better picture.
1. Winkel Tripel
Classification: compromise, modified azimuthal.
Winkel Tripel features a pleasant balance of shape and scale distortion. It has been used by the National Geographic Society since 1998 for general world maps.
2. Eckert IV
Classification: equal-area, pseudocylindrical.
Eckert IV has a nice rounded shape and smooth corners. Mainly used for thematic and other world maps requiring accurate areas.
3. Miller cylindrical
Classification: compromise, cylindrical.
Miller is a modification of theMercator projection so they are almost identical near the equator. Distortion is still severe at the poles. Also used on the simple World map page.
4. Gall Stereographic
Classification: compromise, cylindrical.
Gall resembles the Mercator and Miller projections, but has less distortion of scale and area near the poles. It is used primarily for world maps in British atlases and some other atlases.
Classification: compromise, pseudocylindrical.
TheRobinsonprojection is perhaps the most used compromise pseudocylindrical map projection for world maps. National Geographic used the Robinson projection for about a decade, as well as the CIA. Also used on the World map with microstates page.
6. Van der Grinten I
Classification: compromise, polyconic.
Van der Grinten projects the entire Earth into a circle. It largely preserves the familiar shapes of theMercator projectionwhile modestly reducing Mercator’s distortion.Polar regions are extremely distorted.
Classification: compromise, pseudocylindrical.
The Times projection is similar to Gall stereographic but with curved meridians. Used in The Times Atlas.
Classification: conformal, cylindrical.
The infamous Mercator projection was originally created by Gerardus Mercator in 1569 to display accurate compass bearings for sea travel. As a conformal projection, all local shapes are accurate and correctly defined at infinitesimal scale.
However, it greatly distorts areas as we move away from the equator. That’s why Greenland appears almost the same size as Africa, while in reality it is 1/14th the size. Used for marine navigation and in many street mapping services like Google Maps, Bing Maps, etc.
9. Plate Carrée (equirectangular)
Classification: equidistant, cylindrical.
In Plate carrée a grid of parallels and meridians forms perfect squares from east to west and from pole to pole. It is one of the simplest and oldest map projections and therefore its usage was more common in the past.
Nowadays, it is mainly used for raster datasets, such asCelestiaandNASA World Wind, because of the simple relationship between the position of anpixelon the map and its corresponding geographic location on Earth.
Which projection to choose?
As we saw, there is no single projection that is best for every situation. However, some general rules apply, depending mainly on:
What is the purpose of the map?
If the map is going to be used for measurements or directions, like in navigation or military maps, conformal projections that preserve shape are best.
For maps that show and compare quantitative attributes (e.g. population or GDP) by area or density maps, it would be best to use equal-area projections, as we need to show the true size and area extent of the map’s elements.
General purpose maps, like the world maps you can create on MapChart, should use compromise projections, as a good balance of shape and area distortion is preferable.
Thus, my top recommendation for world maps would be to choose one of either Winkel Tripel, Miller cylindrical or Robinson. I feel that these compromise projections not only strike a nice balance in their features, but they are also widely-used and familiar to a large audience. You really cannot go wrong with one of these.
The other three compromise projections (Gall stereographic, Times and van der Grinten I) would work well too, albeit they may seem a bit exaggerated for many people.
Which part of the world does your map show?
Moving away from world maps, another factor to consider is the area of focus of your map.
As we saw above, the three different types of projections by surface (conic, azimuthal, cylindrical) distort Earth’s latitudes differently. More often than not, it makes sense to take advantage of this fact and produce more accurate maps.
The golden rule here is:
- For tropical regions (around the equator), use cylindrical projections.
- Middle latitudes benefit from conic projections.
- For polar regions, prefer azimuthal projections.
For example, in MapChart, the Advanced World map also features a zoom option to focus on a certain smaller continent, country or area.
In the below map, we zoom in and focus on Southeast Asia and Oceania in a modified azimuthal (Winkel Tripel) projection:
The same map on a cylindrical (Miller cylindrical projections) looks better, with less distortion:
A reference table:
With the above knowledge we can now construct a small reference table to help you learn more about the nine available projections on MapChart. You can also use it to quickly find which one is best-suited for your map.
|Projection||Type by surface||Type by preserved property||Suitable for general world maps||Latitude shown with minimal distortion|
|Winkel Tripel||modified azimuthal||compromise||yes||polar regions|
|Eckert IV||pseudocylindrical||equal-area||yes (for density or thematic)||equator|
|Van der Grinten I||polyconic||compromise||yes||middle latitudes|
Please note that this is just a recommendation and not absolute rules. You should always do your own research and take into account many other factors before choosing.
Where can I learn more about projections?
In compiling this quick guide, I found many useful resources in the general issue of cartography and geography, and specifically map projections. Here are some of them (all freely available):
- Vox’s video on map projections is a great and fun introduction to the issue.
- Simple primers on what a map projection is by GISGeography, Tom MacWright and Axis Maps.
- Wikipedia’s entry is also very informative and easy to understand.
- Radical Cartography has a well-resourced list of projections, their use and characteristics.
- A more extensive list by the professionals in the field, ArcGIS.
- An even more extensive list, also classifying projections by their surface type, by CSISS.
- Great notes from a geography course on Hunter University. The lecture on how to choose a projection is really comprehensive.
Of course, I would always recommend visiting the Advanced World map page on MapChart, where you can check out nine of the most popular projections in action. There you can also toggle other geographical features to fully customize and create the best map for your needs.
Hope that this has helped you in learning more about the broad topic of map projections. I will keep this post updated with new projections that will be added in the future on MapChart.