Cartographic projections are a fundamental tool in the world of cartography, the science that is responsible for graphically representing the Earth's surface on maps. Since the Earth is a three-dimensional sphere, but the maps are two-dimensional planes, it is necessary to transform the information from the sphere to a flat surface. There are various types of map projections different.
In this article we are going to tell you about the types of cartographic projections that exist, their characteristics and importance.
What are map projections
In geography, map projection is a way of visually representing a portion of the Earth's crust by equating the natural curvature of the Earth with the flat surface of a map. It basically consists of "transforming" a 3D rendering into a 2D rendering, distorting the original proportions as little as possible.
This is typical of the process by which a cartographer creates a map and must be guided by the coordinate system formed by the Earth's meridians and latitude to establish a spatial representation that is faithful to the proportions of the Earth's curvature. However, this cannot be done without some margin of error, so projections are studied to minimize distortion and, first of all, preserve three fundamental aspects of maps: distance, area, and shape. If you are interested in the impact of maps on meteorology, you can read about the synoptic maps which are essential to understand the climate and analyze the effects of climate change in cartographic representation.
There may be different cartographic projections, that is, different methods and procedures to represent the size of the Earth (or part of its surface) in two dimensions, since this has been a matter of concern for geographers since ancient times. In this sense, neither is "more faithful" than the other, but they pose different geometric problems and emphasize different aspects of representation.
Types of map projections
To classify a cartographic projection, the criterion of the geometry that inspired it is usually used, that is, if the projection is cylindrical, conical, azimuthal or combines aspects of the three categories. These are the types of cartographic projections that exist:
- cylindrical projection. As the name suggests, these are projections that use an imaginary cylinder as the map surface. The cylinder sits tangent to the spherical surface of the planet, which has good consistency (it respects the shape), but as we move away from the equator, there is a larger and more pronounced distortion in terms of distance and surface area. Even so, by maintaining perpendicularity between meridians and parallels, it is a simple and useful type of projection widely used for navigation and representation of areas affected by drought.
- conical projection. Similar to cylindrical projections, these are obtained by placing the Earth's sphere within the internal curvature of an imaginary tangent or secant cone, onto which lines of latitude and meridians are projected. The advantage of this type of projection is that it converts the meridians into straight lines from the poles and the parallels into concentric circles within a cone. The resulting map is well suited for representing mid-latitudes, making it useful when studying phenomena such as temperature records in Spain, as it becomes more distorted as one moves towards the poles.
- azimuthal projection. Also known as zenith projections, they are obtained by placing the Earth's sphere on an imaginary plane tangent to the sphere itself, onto which the meridians and parallels are projected. The viewpoint obtained corresponds to the view of the world seen from the center of the Earth or from a distant planet. These projections are very good at preserving the relationship between the poles and the hemisphere, so they are accurate at high latitudes; however, the greater the distance between the plane and the tangent point of the sphere, the more they become distorted, so they are not suitable for representing large areas, such as those that could disappear due to the global warming.
- Modified projection. Also called composite or hybrid projections, are those projections that incorporate different aspects of the projections listed above and attempt to faithfully represent the Earth's surface by breaking the continuity of the map and the mathematical construction of squares that contain the same surface of the Earth. It is a counterintuitive procedure, but it allows experimenting with voluntary deformations of the meridian and the terrestrial parallel to obtain new and impossible results with the rest of the projection types.
How to do it
It is technically impossible to represent the Earth on a flat surface without distorting some geometric properties. The complexity of representing an Earth-like shape on a flat surface can be addressed to some extent with a tool called a map projection, which allows the transformation of a spherical shape into a plane, including the lines of latitude and longitude, so that all objects between the corresponding relationship. For this, rigorous mathematical methods are absolutely necessary.
Simply put, map projections are an invaluable resource for creating maps so that their dimensions, properties, and locations within the Earth's curve resemble reality. If you're interested in learning more about the importance of projections in climate studies, check out the article on the coldest countries on the planet, which uses maps to illustrate crucial climate data.
All map projections present characteristics related to the type of transformation or the geometric process used to achieve the transformation. Thus, a geographic projection can have one or two of the following three properties, but in no case can all three be satisfied simultaneously:
- equidistance: The projection is faithful to the original distances, that is, it does not enlarge or reduce them, but rather maintains their proportions on the corresponding scale.
- Equivalence: The projection is faithful to the original surface area, that is, it does not distort the size and dimensions of the surface.
- Accordance: The projection is faithful to the shape and angles of the original, that is, it does not distort the profile or the appearance of the surface it represents.
In each projection, efforts are made to respect these three fundamental properties as much as possible, although some are usually sacrificed more than others depending on the specific use of the projected map. For example, if it is a world map or a flat school sphere, in general the shape of the continents is respected more than the distance between the continents and the surface of each continent.
Other types of map projections
These are other lesser-known types of projections:
- pseudoconical: Parallel lines are represented by concentric arcs and meridians by concurrent curved lines. The central meridian is a straight line.
- pseudocylindrical: Parallels and central meridians are shown as straight lines. Meridians are parallel curves.
- Polyconic: The parallels of latitude are represented by non-concentric arcs with their centers on the central meridian. Additionally, for a better understanding of cartography in relation to climate, you can consult hurricanes in the Pacific Ocean involving the representation of cartographic data in extreme weather events.
No map projection is perfect, but they minimize distortion of area, direction, position, distance, and shape. The use of a given map and a given map projection depends on individual requirements, as each has advantages and disadvantages. For example, to focus on low latitudes, it is best to use a cylindrical projection map, a conical projection for mid-latitudes, and an azimuthal projection for polar regions.
I hope that with this information you can learn more about the types of cartographic projections that exist and their characteristics.
