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map projection — English
A method by which the curved surface of the Earth is represented on a flat sheet of paper. We call such a representation of reality a map. The most important characteristic of a map is that each point on the map corresponds to only one point of the reality (that is, a specific point in the area that is represented on the map). Map projection involves the construction of a grid of two sets of intersecting lines. These lines represent the imaginary grid of latitudinal lines (called parallels) and longitudinal lines (called meridians) on the Earth’s surface. Another way of explaining what map projection is, is that it is a method of transferring the grid system from the Earth’s curved surface to the flat surface of a map. The process of representing a curved shape on a flat plane, demands that either the shapes of the objects or the directions among them, are distorted. This implies that when a sizable portion of the Earth’s surface is mapped, a choice has to be made: should the map be true in terms of the shapes of the objects (such as continents or water bodies), or should it be true in terms of the directions. It is impossible to represent a curved surface on a flat plane without some distortion, and the type of projection used, determines whether the shapes or the directions are distorted. There are many different types of projections in use today and the map-maker has to choose which type of distortion is more acceptable for the purposes of the map user. There is a third way to approach the choice of the map projection to use, namely the decision that neither the shape nor the direction is perfectly correct, both are somewhat distorted, but the final product satisfies the purpose for which the map is made. The most well-known example of such a “projection of convenience” is the Robinson projection that is used by the National Geographic Society. All the global maps in the National Geographic Magazine are based on the Robinson projection. It distorts both shape and direction, but to a relatively small degree, and that is why the National Geographic Society selected this projection.
