Information Access and Distribution Development

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		Elevation Derivatives for National Applications (EDNA) The recent completion of the National Elevation Dataset (NED) and the National Hydrography Dataset (NHD) has provided an avenue for nation-wide development of topographically derived hydrologic data layers at a scale of 1:24,000. Some of the benefits of a nation-wide development of hydrologic derivatives can be summarized as: Program Background Interactive Map