Each series of maps has its own set of symbols that are shown either in the margin, on a separate accompanying sheet, or on a page at the beginning of an atlas. Many symbols are international in use or vary only slightly from map to map.
Landform symbols, often shown in brown, take several forms. On older maps, short shading lines running up and down the slope (called “hachures”) show hills and mountains; the closer together the lines, the steeper the slope. Modern large-scale topographic maps use contour lines that run around a hill in such a way that the line is always at the same height above sea level. Where contour lines are close together, the slope is steep; along a cliff side they run together. The further apart they are, the more level the land. Usually every fifth line is marked somewhere along its length with a number, showing its height in feet or meters (the marginal information will tell which) above sea level.
Water features, often shown in blue, show everything from oceans, rivers, and canals to intermittent streams that run only after a rainstorm. Wells and springs may also be marked. The extent to which these features are shown depends on how important water is to life, economy, and/or transportation in the area.
Vegetation may be shown in green, but symbols vary considerably. Solid or shaded green often represents natural woodlands or grasslands, while small green circles in orderly rows generally represent orchards or tree farms.
On small-scale maps, only cities and towns may be named, while large-scale maps will identify prominent roads, public buildings, and other major structures.
Finally, on some maps, both large- and small-scale, red is often used to indicate principal roadways. On large-scale maps, the red will appear between the black edges of the roadway. On small-scale highway maps, red may be used to indicate classifications of roads, such as high-speed, high-capacity highways and rural byways.
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