3. How we represent the Earth Globes and maps The shape of the Earth is a geoid. This means that it is not a perfect sphere: it is f latter at the poles. It is best represented by a globe, which shows the shapes, distances and sizes of the continents without distortion. (8) However, a globe has several disadvantages: it is not easily transportable; we cannot see small details; and it does not allow us to obser ve the entire surface of the planet at once. For these reasons it is most common to represent the Earth on a map. Maps are f lat representations of the Earth's surface that are drawn to scale. There are dif ferent types of maps: Topographic maps contain information about the physical environment (rivers, relief, etc.) and human elements (settlements, farmland , etc.). Thematic maps provide information on specific aspects (physical , political , etc.) and their distribution over the territor y. (11) How do we represent a sphere on a map? Mapmaking is ver y dif ficult because the Earth has a cur ved surface and maps are f lat. To solve this problem, cartographic projections were invented . They are a system that allows the points on the sphere to be transferred to a map. There are dif ferent types of projections and each one represents some areas of the Earth better than others. However, each type of projection distorts shape and size in some way because our planet is not f lat. Cylindrical projection This is obtained by projecting the surface of the globe onto a cylinder. It is the projection that best represents the areas between the tropics. (9 and 10) Conical projection This is obtained by projecting the surface of the globe onto a cone. It is the projection that best represents the areas between the tropics and the polar circles. Azimuthal projection This is obtained by projecting the surface of the sphere onto a plane at right angles to one of the poles. It is the projection that best represents the polar zones. (11) Compare and explain the advantages and disadvantages of globes and maps. Look at your atlas and give examples of different thematic maps. Describe what each type of thematic map looks like. K E Y Q U E S T I O N S 505399_06_125b_b p cilindrica 505399_06_125b_d p cónica ➞ ➞ ➞ 8. Globe 14
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