The Mercator projection is a system for graphically representing the Earth's surface on a plane, in order to make maps. Among the nearly 400 cartographic projections that exist, Mercator's is a type of cylindrical projection..
Gerardus Mercator, in 1569, imagined the Earth inside a cylinder whose diameter was equal to the Earth's equator. Then, he was projecting lines from the center of the Earth to the cylinder. Thus it was representing all the points of the contour of the earth's surface, which when joined together represent the lines of the geographical forms.
The maps obtained by this projection are especially useful for navigation charts, since it allows routes to be traced using a straight line..
Its main advantage is that it represents the geographical shapes very well, keeping the real angles. However, it alters the proportions of land areas as we move away from the equator..
Article index
The Earth has a shape similar to that of an ellipse circling (geoid, with flattened poles and a bulging equator). On this curved surface are the contours of the continents and islands.
This implies a difficulty when trying to represent that curved surface in a plane and for this the geographers use the projections. However, all the projections generate some deformation or distortion with respect to reality and no method accurately represents the real earth surface.
Therefore, there are different types of cartographic projections, each with advantages and disadvantages that can be flat, conical, cylindrical or polyhedral, among others. In this case, the Mercator projection is a cylindrical projection.
To solve the problem of projecting the Earth's surface onto the plane, Mercator imagined the Earth inside a cylinder of the same diameter. Where the major or longitudinal axis of said cylinder coincided with the axis of earth rotation (normal cylindrical projection).
Subsequently, it was projecting imaginary lines from the center of the planet passing through each point of the contour of the Earth's surface until it intercepted the cylinder. Thus, he was projecting each point of the map on the cylinder and by extending it as a plane and joining the points, he obtained a fairly exact image of the earth's contour.
In this case it is a conforming normal cylindrical projection, where the shapes and angles are maintained. Like the distances, but not the relative proportions of the surfaces in the plane.
The map constructed by means of the Mercator projection is also characterized by being oriented with the north upwards and with Europe occupying the center. Although this seems obvious due to the extensive use that is made of this map, the reality is that equally valid maps can be made from different perspectives.
This type of map projection was designed by Mercator to create navigational charts (maps intended for use by seafarers). Since then it has been used for this purpose, considering its ease of tracing constant course routes using straight lines..
On the other hand, its use has become widespread by using it as a real representation of the Earth in other areas. This is how we find it in textbooks, on school wall maps and many other contexts..
However, it has been pointed out that maps constructed using the Mercator projection should not be used for school teaching. This is due to the fact that the relationship of surfaces between continents is deformed..
Thus, the continents with the largest land mass around the equator, maintain a relative surface on the map similar to the real one. However, the continents located north of the equator are larger than real..
The 1885 Gall-Peters projection, which is an equidistant normal cylindrical projection, has been proposed to be used for school purposes. It saves the surface proportions, restricting the Mercator projection for navigation charts, where its characteristics make it efficient..
Online geolocation systems through the INTERNET, such as Google maps, use the Mercator projection. Specifically the so-called Web Mercator Projection or Google Web Mercator, which Google adopted in 2005, and became widespread among online map providers.
This is mainly due to the fact that the mathematical calculations required for its execution are simpler than those of other types of projections. As well as the fact that in this projection the angles are kept as they really are.
The Mercator projection map is ideal for plotting straight-line routes for navigation and includes a geometric formula to correct for distortions by transforming measurements into degrees of latitude. On the other hand, this map projection keeps the angles between points as they really are..
In addition, as already pointed out, the Mercator projection has the great advantage of the lower complexity of the mathematical operations necessary for its realization..
The fundamental disadvantage of the Mercator projection for maps has to do with the proportions of land mass sizes. Near the equator the proportions are maintained, but when moving away from the equator the areas increase with respect to reality.
This is because the projection was made on a cylinder, where only the equator is tangent to it, without compensating for the deformation generated. Points at the height of the equator are parallel to the cylinder, while points away from it are not..
In the latter, the lines that project them intersect the cylinder at diagonal points and further apart from each other. Therefore, the parallels and meridians of the reference system or coordinates are extended towards the north and towards the south..
This has the consequence that when observing a map made with the Mercator projection, we see, for example, Alaska larger than Brazil. However, the reality is that Brazil is 5 times bigger than Alaska.
Just as it also gives the impression that the Iberian Peninsula is almost the same size as Venezuela or Colombia, when they are larger. Similarly, Russia on the Mercator map is seen 7 times larger than Australia, when it only has an area twice as large as this continent..
Another shortcoming of the Mercator projection is that in the generated map, both the north pole and the south pole are outside the area. This is particularly problematic for the South Pole, where the continent of Antarctica is located..
Yet No Comments