What Are Contour Maps?
Contour maps are detailed maps that show both natural and man-made features. Originally developed in the 1600s for military purposes, they are still used today for military purposes and by backpackers and hikers.
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Definition
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A contour map is also called a topographic map. Contour maps are highly detailed maps that show natural and man-made features. The main feature that differentiates contour maps from other maps is the demarcation of elevation through the use of contour lines. Contour lines indicate the elevation of features such as mountains and and depths of items such as lakes.
Map History
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The first topographic map series to cover a single country was developed by cartographers in France in the late 1780s. While previous mapping techniques only showed governmental or private property lines, topographic maps showed both natural and man-made features.
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USGS Map History
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The United States Geological Survey was initially charged with making topographic and geologic maps in 1879. The early methods were crude by modern standards and involved using a method called "planetable surveying" that involved plotting features on a map using a slanted drawing board and sighting device. In the 1930s following the development of modern flight, the USGS incorporated aerial surveys into its mapping activities. Today, many maps are created or modified using aerial photographs and field surveys.
Characteristics
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The main feature on a contour map is the contour line. Closely-placed contour lines indicate a steep slope; widely-spaced contour lines indicate level terrain. On USGS maps, brown lines indicate contour lines. Small buildings are indicated as black boxes; larger buildings are typically mapped using the building's actual shape. Water features, such as lakes, streams or rivers are indicated in blue. Important roads are indicated in red. Trails, smaller roads, railroads and other man-made features are indicated in black.
Tips to Reading a Contour Map
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Become familiar with the scale of the map. USGS maps typically use a scale of 1:24,000, where one inch equals 2,000 feet (or 1 cm equals 240 meters) and each individual map covers about 9 miles north and south by 7 miles east and west. Next, become familiar with the map symbols, using the color system. Index lines indicate elevations. These lines are typically wider than other contour lines. You can determine the distance between contour lines (or contour interval) by checking the scale at the margin of the map.
Where to Get Contour Maps
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You can purchase many contour maps at outdoor stores. USGS topographic maps are available for purchase or download from the USGS website. You can find topographic maps at state or county natural resources departments or online retailers as well.
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