The ways in which we visualize the world are varied- we have pictures, maps, globes, satellite imagery, hand drawn creations and more.
What kinds of things can we learn from the way we see the world around us?
For centuries cartographers have been making maps of the world around them, from their immediate area to the greater world as they understood it at the time. These maps depict everything from hunting grounds to religious beliefs and speculations of the broader, unexplored world around them.
Maps have been made of the local waterways, trade routes, and the stars to help navigators on land and sea make their way to different locations.
Cartographers have been visualizing the world around us, both real and imaginary.
How we visualize the world not only has practical implications, but can also help shape our perspectives of the Earth we live in.
There are many kinds of maps made from a variety of materials and on a variety of topics.
Clay tablets, papyrus, and bricks made way for modern maps portrayed on globes and on paper; more recent technological advances allow for satellite imagery and computerized models of the Earth.
Using a globe versus a map
Using a globe instead of a map offers several advantages:
- Accurate representation: A globe accurately represents the Earth’s curved surface without any distortions in area, shape, distance, direction, or scale. Maps, on the other hand, always introduce some level of distortion due to the process of projecting a three-dimensional surface onto a two-dimensional plane.
- True spatial relationships: A globe allows for a better understanding of the spatial relationships between different locations on Earth. Distances, directions, and relative positions of continents and countries are more accurately depicted on a globe than on a map.
- Better visualization of Earth’s geometry: A globe helps users visualize the Earth’s round shape, making it easier to comprehend concepts such as latitude, longitude, the Earth’s axis, and the rotation that causes day and night.
- Improved perspective: A globe offers a more realistic perspective of the Earth, helping users appreciate the actual size and position of landmasses and bodies of water, which can sometimes be misrepresented on maps due to projection distortions.
- Consistent scale: A globe has a constant scale throughout its entire surface, unlike maps where the scale can vary from point to point depending on the projection used.
Despite these advantages, globes have some limitations, such as being impractical for large-scale mapping, difficult to measure, challenging to see the entire world at once, and less portable compared to folding maps.
What are map projections?
A map projection is a method used to represent the Earth’s three-dimensional, curved surface onto a two-dimensional plane, such as a piece of paper or a digital screen. Since the Earth is not flat, map projections inevitably introduce some distortions in area, shape, distance, direction, or scale.
Cartographers choose different map projections based on the purpose of the map and the region being depicted to minimize these distortions and accurately convey information.
Three of these common types of map projections are cylindrical, conic, and azimuthal.
Types of map projection distortion
Map projections inevitably introduce distortions in one or more of the following aspects:
- Area-preserving projection – Also called equal area or equivalent projection, these projections maintain the relative size of different regions on the map.
- Shape-preserving projection – Often referred to as conformal or orthomorphic, these projections maintain accurate shapes of regions and local angles.
- Direction-preserving projection – This category includes conformal, orthomorphic, and azimuthal projections, which preserve directions, but only from the central point for azimuthal projections.
- Distance-preserving projection – Known as equidistant projections, they display the true distance between one or two points and all other points on the map.
It is important to note that it is impossible to create a map projection that preserves both area and shape simultaneously.
Distortion on a map can be visualized using the Tissot’s Indicatrix. Using graduated circles, the amount of distortion is shown relative to the other areas of the map.
How map projections are categorized
The primary categories of map projections include:
- Cylindrical Projections: These projections involve wrapping a cylinder around the Earth and projecting its features onto the cylindrical surface. Examples are the Mercator, Transverse Mercator, and Miller Cylindrical projections.
- Conic Projections: For these projections, a cone is placed over the Earth, and its features are projected onto the conical surface. Common examples are the Lambert Conformal Conic and Albers Equal-Area Conic projections.
- Azimuthal Projections: Also referred to as planar or zenithal projections, these use a flat plane that touches the Earth at a single point, projecting the Earth’s features onto the plane. Azimuthal Equidistant, Stereographic, and Orthographic projections are examples.
- Pseudocylindrical Projections: These projections resemble cylindrical projections but employ curved lines instead of straight lines for meridians and parallels. The Sinusoidal, Mollweide, and Goode Homolosine projections are popular examples.
Map projections can also be classified based on the properties they maintain:
- Equal-area (equivalent) projections: These projections preserve the correct proportions of areas, such as in the Albers Equal-Area Conic and Mollweide projections.
- Conformal (orthomorphic) projections: These projections maintain local angles and shapes, as seen in the Mercator and Lambert Conformal Conic projections.
- Equidistant projections: These projections retain true distances from one or two points to all other points, as in the Azimuthal Equidistant projection.
- Azimuthal projections: These projections preserve directions from a central point, including some conformal, orthomorphic, and azimuthal projections.
- Compromise projections: These projections attempt to balance various distortions inherent in map projections, such as the Robinson and Winkel Tripel projections.
It is essential to understand that no map projection can perfectly preserve all properties, as each type entails some degree of compromise or distortion.
Cylindrical Map Projections
Cylindrical projections involve wrapping a cylinder around the Earth, touching it at the equator or another standard line, and projecting the Earth’s surface onto the cylinder.
This kind of map projection has straight coordinate lines with horizontal parallels crossing meridians at right angles. All meridians are equally spaced and the scale is consistent along each parallel.
Cylindrical map projections are rectangles, but are called cylindrical because they can be rolled up and their edges mapped in a tube, or cylinder, shape.
The only factor that distinguishes different cylindrical map projections from one another is the scale used when spacing the parallel lines on the map.
The downsides of cylindrical map projections are that they are severely distorted at the poles.
While the areas near the Equator are the most likely to be accurate compared to the actual Earth, the parallels and meridians being straight lines don’t allow for the curvature of the Earth to be taken into consideration.
Cylindrical map projections are great for comparing latitudes to each other and are useful for teaching and visualizing the world as a whole, but really aren’t the most accurate way of visualizing how the world really looks in its entirety.
Types of cylindrical map projections you may know include the popular Mercator projection, Cassini, Gauss-Kruger, Miller, Behrmann, Hobo-Dyer, and Gall-Peters.
Introduced by Gerardus Mercator in 1569, the Mercator projection is a cylindrical projection that preserves local angles and shapes, making it valuable for navigation purposes.
The Mercator map projection significantly distorts the size of landmasses near the poles, leading to misconceptions about the relative sizes of continents and countries.
Transverse Mercator Projection
A variation of the Mercator projection, the Transverse Mercator projection, involves rotating the cylinder 90 degrees.
The Universal Transverse Mercator map projection is commonly used for large-scale mapping of regions with predominantly north-south extents, such as the U.S. Geological Survey’s topographic maps. With UTM, the world is divide into 60 zones that are each six degrees wide.
This projection reduces distortion for areas with limited east-west extents but increases distortion as one moves away from the central meridian.
Miller Cylindrical Projection
Osborn Maitland Miller developed the Miller Cylindrical projection in 1942 as a modified version of the Mercator projection. It minimizes distortion in high latitudes by slightly compressing the spacing of parallels. Although it still overstates the size of polar areas, the distortion is less pronounced than in the standard Mercator projection.
Conic Map Projections
Conic projections involve placing a cone over the Earth, touching it along a standard parallel or two standard parallels. Conic map projections include the equidistant conic projection, the Lambert conformal conic, and Albers conic.
These maps are defined by the cone constant, which dictates the angular distance between meridians.
These meridians are equidistant and straight lines which converge in locations along the projection regardless of if there’s a pole or not.
Like the cylindrical projection, conic map projections have parallels that cross the meridians at right angles with a constant measure of map distortion throughout. Conic map projections are designed to be able to be wrapped around a cone on top of a sphere (globe), but aren’t supposed to be geometrically accurate.
Conic map projections are best suited for use as regional or hemispheric maps, but rarely for a complete world map.
The distortion in a conic map makes it inappropriate for use as a visual of the entire Earth but does make it great for use visualizing temperate regions, weather maps, climate projections, and more.
Lambert Conformal Conic Projection
The Lambert Conformal Conic projection is a conic map projection that maintains accurate shapes and angles over small areas.
This map projection is suitable for mapping regions with predominantly east-west extents, such as the United States. This projection is widely used for aeronautical charts due to its angle preservation, making it valuable for navigation.
Albers Equal-Area Conic Projection
The Albers Equal-Area Conic projection is a conic map projection that preserves the area at the expense of shape and angle.
This map projection is also useful for displaying regions with significant east-west extents, such as the continental United States. This projection is often used for thematic maps requiring accurate area representation, such as population density or land use.
Azimuthal Map Projection
Azimuthal projections involve projecting the Earth’s surface onto a flat plane, typically tangent or secant to the Earth at a specific point.
The azimuthal map projection is angular- given three points on a map (A, B, and C) the azimuth from Point B to Point C dictates the angle someone would have to look or travel in order to get to A.
These angular relationships are more commonly known as great circle arcs or geodesic arcs.
The main features of azimuthal map projections are straight meridian lines, radiating out from a central point, parallels that are circular around the central point, and equidistant parallel spacing.
Light paths in three different categories (orthographic, stereographic, and gnomonic) can also be used. Azimuthal maps are beneficial for finding direction from any point on the Earth using the central point as a reference.
Azimuthal Equidistant Projection
The Azimuthal Equidistant projection is a planar projection that maintains accurate distances from the center point to any other point on the map. This projection is frequently used for polar maps, where the center point represents the North or South Pole.
This map projection is also commonly utilized for radio and telecommunications planning, as it accurately represents distances between the central point and other locations.
The Stereographic projection is a planar projection that preserves angles and shapes locally, making it conformal. It is often used for mapping polar regions and creating star charts in celestial cartography.
This map projection is also the basis for the popular Polar Stereographic projection, which is used for representing high-latitude regions with minimal distortion.
The Orthographic projection is a planar projection that represents the Earth as if viewed from an infinite distance, giving the appearance of a globe on a flat surface.
This projection is often used for artistic purposes and for visualizing the Earth from space, as it provides a unique, aesthetically pleasing perspective.
Pseudocylindrical projections resemble cylindrical projections but have curved parallels instead of straight ones.
The Sinusoidal projection, also known as the Sanson-Flamsteed projection, is an equal-area pseudocylindrical projection that minimizes distortion in the east-west direction near the equator. It is often used for world maps that prioritize accurate area representation, such as climate or vegetation maps.
The Mollweide projection is a pseudocylindrical equal-area projection that balances area and shape distortion, making it suitable for world maps that require a reasonable compromise between these properties.
The Mollweide Projection is frequently used for thematic maps, such as those illustrating global temperature patterns or population distribution.
Equal Earth Map Projection
The Equal Earth map projection is a relatively new pseudocylindrical projection designed to display the entire Earth’s surface with minimal distortion while preserving equal areas.
The Equal Earth map projection was developed by contemporary cartographers Tom Patterson, Bernhard Jenny, and Bojan Šavrič in 2018 as a response to the increasing need for a visually appealing and less distorted world map that accurately represents areas, especially in the context of global issues like climate change and deforestation.
The Equal Earth projection is inspired by the Robinson projection and maintains the same overall shape, but with improved area accuracy. It is particularly well-suited for general-purpose world maps, educational materials, and thematic maps that require an equal-area representation. This projection is advantageous because it presents a balanced view of the world, with less emphasis on the size of high-latitude countries, avoiding the common misconceptions caused by projections like the Mercator, which significantly exaggerates the size of regions closer to the poles.
Goode Homolosine Projection
The Goode Homolosine projection, developed by John Paul Goode in 1923, is a pseudocylindrical equal-area projection that resembles an interrupted globe. It is designed to minimize distortion in both area and shape, making it suitable for world maps that require a balanced representation of the Earth’s landmasses.
Compromise projections aim to strike a balance between the various distortions inherent in map projections.
The Robinson map projection, developed by Arthur H. Robinson in 1963, is a compromise projection that balances the distortions of area, shape, distance, and direction.
It creates visually appealing world maps that provide a general overview of the Earth’s surface. The National Geographic Society widely used the Robinson projection for its world maps until 1998.
Winkel Tripel Projection
The Winkel Tripel projection, developed by Oswald Winkel in 1921, is another compromise projection that balances distortions in area, shape, distance, and direction.
It is considered one of the best projections for general-purpose world maps, and the National Geographic Society adopted it as their standard world map projection in 1998.
Different types of map projections suit different geographic needs
Map projection types all have their pros and cons, but they are incredibly versatile.
Even though it is nearly impossible to create an entirely accurate map projection there are uses for even the most imperfect depictions of the Earth.
Map projections are created for certain purposes and should be used for those purposes. In the end each and every map projection has a place, and there is no limit to the amount of projections that can be created.
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This article was originally written on March 6, 2015 and has since been updated.