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Verifying map features Verifying map featuresField personnel use aerial photographs to mark and verify map features. A field check is necessary because information on an aerial photograph can often be ambiguous. For example, a worker in the field can indicate the difference between a perennial stream and one that dries up at certain times of the year. This is necessary because a perennial stream would be marked with a solid line on a map while an intermittent stream is designated by either a dash-dot or lighter weight solid line on a map. People who know the local area well, such as fishermen or farmers, are excellent sources of such information.Another important job in the field is the verification of place names and political boundaries. This work often requires looking at courthouse records and talking to local residents. It can even include a visit to the local cemetery to check the spelling of a feature that has been named after a person buried there. Significant changes in map content on successive editions of a map of Key Largo, Florida, illustrate why maps need revision.

What's in a Name? What's in a Name?Almost 2 million natural and manmade features are identified in the USGS topographic map series. These geographic names form a primary reference system essential for the communication of cartographic information. Beyond map labeling, geographic names are part of the Nation's living heritage. The origins and meanings of geographic names, derived from many languages, show national, personal, and social ingredients of life, past and present.Some of the oldest geographic names found on U.S. maps are from Native American languages. Names like Adirondack, Chippewa, Chesapeake, Shenandoah, Choctaw, Yukon, and the names of 28 States are derived from various Native American languages. Other names reflect the European naming traditions of the early settlers. New London, Yorktown, Grover Hill, and Lancaster are derived from English; Fond du Lac, Baton Rouge, Marietta, La Salle, and St. Louis are French; El Mirage, Guadalupe, Rio Grande, San Francisco, and De Soto are Spanish names.U. S. Geographic names are often rich in description, local color, and national history. Names like Stone Mountain, Ragged Ridge, Big Muddy River, Carmel-by-the-Sea, Grandview, and Long Island paint descriptive pictures of the places, features, and areas they represent. Last Chance, Hells Canyon, Liberty, Thief Lake, Enterprise, Rattlesnake Creek, Dread and Terror Ridge, and Paradise Flats evoke the dreams, fears, and color of the frontier.The standardization of geographic names in the United States began late in the 19th century. The surge in mapping and scientific activities after the Civil War left the accuracy and spelling of a large number of names in doubt. This posed a serious problem to mapmakers and scientists who require nonconflicting nomenclature. The U.S. Board on Geographic Names was established in 1890 as the central authority to deal with naming conflicts. This interagency body, chaired by the U.S. Department of the Interior, helps standardize the spelling and application of geographic names on maps and documents published by the U.S. Government.|| Top ||

Survey measurements are taken carefully to establish the contr Survey measurements are taken carefully to establish the control points that become the framework on which map detail is compiled. Two types of control points are needed to position map features accurately. Horizontal control points identify the latitude and longitude of selected features within the area being mapped. They establish correct scale and map orientation and allow accurate positioning of the map's features. Vertical control points determine the elevation of selected points for the correct placement of a topographic map's contours.Rigorous standards ensure USGS map accuracyMarkers such asthis are placed in the field by USGS survey teams to establish control points for maps. Because engineers, highway officials, land use planners, and other professionals use USGS topographic maps as tools, map accuracy is vital. Dependable maps are also important to campers, hikers, and outdoorsmen.The National Map Accuracy Standards were developed to ensure that Federal Government maps meet the high expectations and requirements of such users. Originally issued in 1941, the National Map Accuracy Standards apply to all Federal agencies that produce maps. These standards require horizontal and vertical map precision. For example, at least 90 percent of horizontal points tested on a 7.5 minute, 1:24,000-scale map must be accurate to within one-fiftieth of an inch on the map (40 feet on the ground). Vertical testing requires that at least 90 percent of the elevations tested must be accurate to within one-half the map's contour interval. For example, on a map with a contour interval of 10 feet, tested points must be within 5 feet of the actual elevation. These and other standards of accuracy and content ensure consistency in both the detail and the appearance of maps. They also ensure compatibility among USGS maps made at different times.