Azimuth Projection: Types, Uses, Advantages, Disadvantages and Main Characteristics

The azimuthal projection , also called azimuthal projection and zenith projection, consists of the geographical projection of the Earth on a flat surface. The main intention of this projection is to obtain a vision of the globe from the center of it or from outer space.

It is the reflection that is obtained on a tangent plane (for example, a sheet of paper), taking into account the meridians and parallels, which end up transmitting a set of features and characteristics of the sphere to that other element.

In general, the reference points for this projection are usually any of the poles. However, it can be done from any point on Earth. It is important to note that the azimuthal projection refers to the mathematical term"azimuth", which is believed to come from Arabic and which refers to distances and trajectories.

Through the azimuthal projection the closest distances between two points of the planet can be located, taking into account the maximum circles of the circumference. Therefore, this type of projection is used for orthodromic navigation, which seeks to follow the path of the maximum circles to travel the shortest distance between two points.

History

Some scholars claim that the ancient Egyptians were the pioneers in the study of the heavens and the shape of the Earth. Even some maps can be found in sacred books.

However, the first texts related to the azimuthal projection appeared in the eleventh century. It is from there that develops the study of geography and maps, whose evolution flourished during the Renaissance.

At that time, sketches were made on the continents and countries. The first to do so was Gerardo Mercator, who made the famous map of 156. Later on he was followed by the Frenchman Guillaume Postel, who popularized this projection under the name of"Postel projection", which he used for his 1581 map.

Even today, the influence of this projection on the emblem of the United Nations Organization can be seen.

Main characteristics

- The meridians are straight lines.

- The parallels are concentric circles.

- The lines of the longitudes and latitudes are intercepted forming angles of 90 °.

- The scale on the elements near the center is real.

- The azimuthal projection generates a circular map.

- In general, the poles are considered as central points for the realization of the projection.

- The resulting maps can preserve values ​​in terms of equidistance, area and form.

- It is characterized by having radial symmetry.

- The address is correct as long as it goes from the central point or element to another.

- Generally it is not used near the equator because there are better projections in this area.

- Displays distortions as you move away from the center point.

To understand the projection of any type, it is important to take into account that it is based on mathematical concepts to obtain the best possible result in terms of the terrestrial image.

For this, the following concepts are considered:

- Equidistant projection

It is that projection that conserves distances.

- Equivalent projection

It is about the projection that preserves the surfaces.

- Conformal projection

Preserves the shape or angle relationship between the points studied.

In the end, this indicates that no projection actually allows these three elements to be conserved since mathematically it is impossible because it takes as reference an element with spherical dimensions.

The 2 main types of azimuthal projection

1- When there is perspective projection

Stereographic projection

This considers an opposite extreme point in the globe. The most common example is when the poles are used as reference, although in that case it would be called polar projection.

It is also characterized because the parallels become closer as they go towards the center, and each circle is reflected as a semicircle or as a straight line.

Orthographic projection

It is used to have a vision of the hemispheres, but from the perspective of outer space. The area and the form are distorted and the distances are real, especially those that are around the equator.

Gnomish projection

In this projection all the points are projected towards a tangent plane, considering the center of the Earth.

It is usually used by navigators and pilots because the circular patterns of the meridians are shown as straight lines, showing shorter routes to follow.

It should be noted that although there are technological advances through which it is easier to find these routes, the use of paper still persists.

2- When there is no perspective projection

Equidistant azimuthal projection

It is usually used for navigation and trips to the polar areas, so the air-route distances stand out. The measurements from the center are real.

Azimuthal projection of Lambert

With this projection it is possible to see the whole Earth but with angular distortions. That is why it is used especially for the construction of atlas, starting from east to west.

Oblique lines allow the inclusion of continents and oceans. Also, among its uses is the mapping of small countries and islands.

Applications

- The azimuthal projection allows orthodromic navigation, which consists of finding the minimum distance from one point to another, from the air or the sea.

- Allows the creation of maps for small and compact places, as well as universal atlases.

- Seismologists use gnomic projections to determine seismic waves, as these move in the form of large circles.

- Assistance to the radial communications system, since the operators use the azimuth projection to locate antennas according to the angles they establish in the maps.

Advantage

- Intercept the Earth according to the different laws on perspectives.

- When the center of the projections is at the poles, the distances are real.

- It provides a great projection of the maps of the Arctic and the Antarctic, as well as of the hemispheres.

- The representation of the poles does not show distortion, because it increases at the equator.

Disadvantages

- The distortion will be greater as the distance increases, from a point on the flat surface to the surface of the balloon.

- It does not allow to represent the Earth in its totality, unless it presents distortions.

References

1. Azimuthal projections: Orthographic, Sterographic and Gnomonic. (2018). In GISGeography. Retrieved: February 15, 2018. In GISGeography of gisgeography.com.
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3. Azimuthal projections. (s.f) In Lazarus. Retrieved: February 15, 2018. In Lazarus de lazarus.elte.hu.
4. Fundamental of Maping. (2016). In ICSM. Retrieved: February 15, 2018. In ICSM of icsm.gov.au.
5. Azimuthal projection. (2013). In Map Engineering. Retrieved: February 15, 2018. In Ingeniería de Mapas de ingenieriademapas.wordpress.com.
6. Azimuthal projection. (s.f) In Wikipedia. Retrieved: February 15, 2018. In Wikipedia of es.wikipedia.org.
7. Azimuthal projections. (s.f) In UNAM. Retrieved: February 15, 2018. In UNAM of arquimedes.matem.unam.mx.