The American Revolution and Its Era: Maps and Charts of North America and the West Indies, 1750-1789
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Maps and Art: The Problem of Scale
Scale is an issue that must be dealt with in preparing any visual representation that bears some resemblance to reality. Scale is the relationship between the size of an object in reality and the size at which it is depicted in the visual representation.
In many art forms, scale can be distorted or exaggerated for effect. Think about political cartoons, for example. In cartoons, a physical feature is often exaggerated as a way to satirize the person depicted (think of Mikhail Gorbachev's birthmark, Jay Leno's jaw). In creating maps, architectural drawings, or engineering plans, however, precision in rendering the scale is important.
Selecting the scale to be used is an important step in beginning to draw a map. The scale on many maps is shown using an image that resembles a ruler. A certain measurement (often an inch) is shown, marked off to indicate the miles represented by each segment of an inch on the map. The scale can also be represented as a ratio, as in 1:50. The ratio means that 1 unit of measurement on the map (such as an inch) is equal to 50 of the same units in reality.
The way in which the scale of a map is referred to can be confusing. A small-scale map is one in which the scale ratio, if expressed as a fraction, is very small. Thus, the second number in a small-scale map's scale is large — and the area represented on the map is large. For example, a scale of 1:15,000,000 (or 1/15,000,000) would be a small-scale map. On a large-scale map, the scale expressed as a fraction is larger because each unit on the map represents less distance in reality. The second number in a large-scale map's scale is small — and the area represented in the map is small.
Looking at some actual maps from the collection may clear up the confusion.
- Examine the following maps, noting the scale of each as a fraction:
Bowles's new pocket map of North America
A map of the British and French dominions in North America
A chart of the harbour of Rhode Island and Narraganset Bay
A map of the Federal Territory from the western boundary of Pennsylvania to the Scioto River
Plan of the heights of Charles Town
- Use the fractions to arrange the maps in order from largest scale to smallest scale.
- Now look at the maps again and arrange the maps in order from the one showing the smallest area to the one showing the largest area. What do you notice about the two lists?
- Again, compare the maps. What are the advantages of large-scale maps? What are the advantages of small-scale maps?
- Write a paragraph describing when a mapmaker might choose to make a large-scale map and when he/she might choose to make a small-scale map. Give examples from The American Revolution and Its Era and from a contemporary map collection.