USGS National Map

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 to provide a composite topographic base map.

来自国家地图（The National Map）的美国地质调查局（USGS）地形底图服务，将等高线、地貌晕渲、林地与城市色调及各类矢量图层进行整合，以此提供复合式地形底图。