An azimuthal projection is a map of the world that has useful properties because all points on the map are at proportionally correct distances from its center point. One of the most common ways to use this approach is through a polar projection from the north or south. All of the meridians, the lines of longitude, are straight in this image, with the distances from the poles represented correctly.
The first azimuthal projects may have been present in ancient Egypt. Archeologists have found star maps that take this approach in some of the earliest holy books. The 11th century works by al-Biruni also describe the equidistant projection that this approach to mapmaking utilizes.
Many Renaissance maps use this projection, with the most famous examples coming from Gerardus Mercator and Guillaume Postel. Since the circumference of the planet is about 40,000 kilometers, the maximum distance this approach can use is about 20,0000 kilometers. If a distance is less than 10,000 kilometers, then the distortions are minimal.
Several azimuthal projection advantages and disadvantages are worth reviewing when looking at this approach to mapmaking.
List of the Advantages of Azimuthal Projection
1. The azimuthal projection can operate in a variety of ways.
You can use a perspective-based or a non-perspective-based application when using the azimuthal projection. If you’re using the first option, then you can use a stereographic, orthographic, or Gnomish projection. That means you can consider the opposite extreme point on the globe, have a vision of the hemispheres from an outer space perspective, or have all points projected toward a tangent plane respectively.
When using the second option, you can choose from an equidistant azimuthal projection or an azimuthal projection of Lambert. The former is useful for trips or navigation to the polar regions so that the air-route distances stand out, with the measurements from the center being real. The latter allows one to see the entire planet but through the lens of angular distortions.
2. It allows for orthodromic navigation.
The azimuthal projection provides navigators with an opportunity to find the minimum distance from one point to another. Although land-based calculations are available with close-range maps, it is particularly useful for long-distance travel from the sea or the air.
3. This projection remains useful in a variety of sizes.
The azimuthal projection design allows for the creation of maps that take the shape of a universal atlas or for compact and small places. If you’re using a paper-based map to navigate through a city, then there is an excellent chance that it incorporates some of the elements of this mapmaking approach. Many apps that incorporate maps as part of their features will also use this approach with the visible projection to help you find where you are.
4. It can avoid some of the issues of distortion that other projections must include.
When using the azimuthal projection, the distances are real when the center is at the poles. That’s why it is the primary option when creating a map of the Arctic or the Antarctic regions of our planet. Because the shape of our planet expands outward as we approach the equator from the North or South Pole, the projection adapts to create distances that remain real as you follow the longitudinal lines.
That means you can receive a map with zero distortion when using the azimuthal projection in this manner. It is also useful in this situation when developing a map of a hemisphere.
5. Seismologists can use the azimuthal projection for specific purposes.
The azimuthal projection gives seismologists another tool to use when making gnomic projections because it allows them to determine seismic waves. These incidents move in the form of large circles that are easier to track when using this map’s specific approach. The calculation of angles makes it simpler to determine impact zones for traveling phenomenon in a manner that’s similar to how operators of our radial communications system use it to calculate antenna angles.
6. It creates a natural point of reference.
When creating an azimuthal projection, there is a natural point of reference that starts the mapmaking process. Any geographic location on our planet can become the foundation of this work. That makes it a useful method of charting a specific location in its relation to another point of reference. Although the distortions can become bothersome from a viewer perspective, the maps that don’t focus on the poles tend to look at the angle of direction more than an accurate view of the distance. That’s why it is a favorite option for those who must calculate specific outcomes.
7. You can create a linear cartogram with an azimuthal projection.
One of the most useful variants of an azimuthal projection is called a linear cartogram. This option will omit political boundaries and coastlines, along with most other physical features. It will show cities with distances to the center that’s adjusted to portray travel times, transportation costs, or some other key performance indicator that measures relative distance or accessibility.
If the relative area is important in some way, then an equal-area or locally-centered azimuthal projection is appropriate since distortion of the shape is minimal near the center and extreme at the margins.
8. The stereographic projection is the only known perspective projection that’s also conformal.
This advantage is another reason why the azimuthal projection often focuses on the polar regions of our planet. It uses the point-based perspective to create accurate representations of the landmasses that are between them. Whether it projects all great circles to straight lines or uses a different angle of approach, it creates an accurate representation in specific circumstances that allow for simple observation and study.
List of the Disadvantages of Azimuthal Projection
1. It applies well when looking from a polar perspective only.
The distortions that occur with an azimuthal projection make it a map that works best when looking at the planet from a polar perspective. Maps of the Arctic and Antarctic are particularly excellent when using this approach. If a map of a hemisphere is necessary, then this option tends to work better than other types.
When you use the azimuthal projection to focus on a specific location outside of the poles, the distortions of this map become distracting. Although it is useful for close distances, anything that is more than 10,000 kilometers away will not receive an accurate representation.
2. A perspective azimuthal projection cannot plot out the entire Earth.
If you need to have a map of the entire planet, then a perspective-based azimuthal projection cannot provide a useful outcome. It only provides a hemispheric result with accuracy at best because it incorporates the direct perspective of the individual looking at the map. Your only option when taking this approach to mapmaking is to use a non-perspective azimuthal projection.
The latter approach might create a usable outcome, but it is also one that isn’t directly reflected in reality. Its central point of focus will always come with the most priority to the viewer. That means the distortions will become significant once you begin moving outward to the outer edges of the projection.
3. Distortions increase as the distance expands on the map.
When using the azimuthal projection, the distortions will continue to increase as the distance between the plotted object gets further away. It’s similar to the effect you would experience when moving from a point on the flat surface to one that’s on a balloon. Only the central perspective remains accurate with this result. Although the purpose is to create a perspective that feels authentic from an outside view, especially with an outer space perspective, the distortions along the edge of the map can get problematic in some perspectives.
You can never represent the Earth in its totality, even with a non-perspective approach, without presenting the final map with distortions of some type.
4. It creates an awkward perspective when used for centering purposes.
When looking at a map of the entire world, the way a projection gets centered impacts where distortion is minimal and where severance may happen. That’s why you rarely see an equatorially-based azimuthal projection that focuses on North America. The awkward position of that continent in relation to Asia creates a massive level of distortion that could make the map unusable for most people.
Even strictly symmetrical projections might cut off the eastern tip of Siberia or separate the western islands from the Aleutian chain in Alaska. That’s why it tends to be useful for air and sea navigation, but not individualized land-based transportation needs.
5. The azimuthal approach doesn’t charge small landmasses well.
When you look at an azimuthal projection, the primary points of focus involve the continents as depicted on the map. That means an Arctic one would focus on North America as an example of this disadvantage. If your primary reason for the projection is to navigate to or around specific islands, it can be a challenge to pinpoint specific small locations because of the scope of this map.
If you were to take an azimuthal projection with an equatorial stereographic approach, then North and South America would become the primary point of focus. You’d see Greenland and Antarctica, albeit with some distortion. Hawaii is noticeable for those familiar with the chain. The other small Pacific islands are either not directly charted or too small to recognize.
An azimuthal projection is useful for terrestrial point-to-point communication. The map allows an operator to quickly determine the direction in which they need to point their directional antenna. You would find the location on the map for the target receiver or transmitter, determine the azimuth angle, and then use an electric rotator to complete the action. It works with one-way or two-way communication efforts.
We also use the azimuthal projection to determine the range of missiles, the time of a flight, and other needs that have specific starting and ending points.
The advantages and disadvantages of the azimuthal projection allow us to consider specific regions of our planet for a variety of needs. It might not be the most useful map in specific applications, but it does offer a way to consider distances in ways that other projects don’t offer.
Brandon Miller has a B.A. from the University of Texas at Austin. He is a seasoned writer who has written over one hundred articles, which have been read by over 500,000 people. If you have any comments or concerns about this blog post, then please contact the Green Garage team here.