Читать книгу Geography For Dummies - Jerry T. Mitchell - Страница 67

Accordingly, this chapter is about mapmaking with emphasis on the distortions that are inherent in flat maps of the world. But first, some basic vocabulary is in order. A map is a representation of all or part of Earth’s surface. Cartography is the field of mapmaking, and a cartographer is a person who makes maps. Way back when, cartography was pure freehand, and I do mean way back. The oldest known map is a 5,000-year-old clay tablet that shows physical features of Mesopotamia. Later, cartography became associated with instruments and techniques that most people think of as drafting. Nowadays, most cartography is done using a computer.

Flat maps are called projections because, theoretically, making a map of the world or a large part of it involves projecting a globe onto a piece of paper or similar flat surface. Imagine, as shown in Figure 4-1, a clear plastic globe with a light source at its center. When the bulb is turned on, light passes through the glass sphere and projects the lines from the globe’s surface onto a receiving flat surface. The result is a flat map of Earth — a projection.

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FIGURE 4-1: Map projection.

Projection has two meanings. On the one hand, it refers to the process of transferring a globe to a flat surface. On the other hand, projection refers to the map itself, the result of the transferal. One could say, then, that projection (transferal) results in a projection (flat map).

The diagram that shows the globe and light bulb is a simple model that most people find helpful in visualizing how projections are made. In reality, projections aren’t made with a glowing light bulb in the center of a globe. Instead, projections are products of mathematical formulas, trigonometric tables, and things of that ilk. The specifics are pretty tedious; fortunately, trying to explain it all in language that even I can understand is beyond the scope of this book. It will be sufficient for you to appreciate that different projections exist, but none are totally truthful.