USGS National Map
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资源简介：
The USGS Topo base map service from The National Map is a combination of contours, shaded relief, woodland and urban tint, along with vector layers, such as geographic names, governmental unit boundaries, hydrography, structures, and transportation, to provide a composite topographic base map. Data sources are the National Atlas for small scales, and The National Map for medium to large scales. Source: U.S. Geological Survey (USGS), National Geospatial Program – The National Map
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Esri创建时间：
2014-12-01
