Most USGS topographic maps use brown contours to show the shape and elevation of the terrain. Contour intervals vary, depending mainly on the type of terrain and the scale of the map. (Scale is the relationship between distance on the map and distance on the ground.)
The maps show and name prominent natural and cultural features. Those at scales of 1:24,000 (1 inch = 2,000 feet) show an area in detail. Such detail is useful for engineering, local area planning, and recreational purposes.
Less detail is shown at scales of 1:50,000 (1 centimeter = 0.5 kilometer) to 1:100,000 (1 centimeter = 1 kilometer). They cover larger areas and are used in land management and planning.
Maps at scales of 1:250,000 (1 inch = about 4 miles), 1:500,000 (1 inch = about 8 miles), and 1:1,000,000 (1 inch = about 16 miles) cover very large areas on each sheet and are used in regional and statewide planning.
Areas featured. Most USGS map series divide the United States into quadrangles bounded by two lines of latitude and two lines of longitude. For example, a 7.5-minute map shows an area that spans 7.5 minutes of latitude and 7.5 minutes of longitude, and it is usually named after the most prominent feature in the quadrangle. Others show a whole area—a county, State, national park, or place of special interest
The best known USGS maps are those of the 7.5-minute, 1:24,000-scale quadrangle series. A scale of 1:25,000 is used for maps based on metric units (1 centimeter = 0.25 kilometer). The area portrayed on each sheet ranges from 64 square miles at latitude 30 degrees north to 49 square miles at latitude 49 degrees north.
A scale of 1:24,000 allows considerable detail to be shown in the quadrangle areas. It takes about 57,000 maps to cover the conterminous 48 States, Hawaii, and territories. |
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