The primary types of topographic changes resulting from human geomorphic activity include surface mining, road construction, urban development, dam construction, and landfills. The National Land Cover Dataset (NLCD) provided land cover information at a 30-meter resolution that matched the NED and SRTM data. Historical NED data values were subtracted from the recently collected SRTM data to determine significant topographic changes. The need for more comprehensive information on the nature and extent of recent human geomorphic activity led to a spatial emphasis for the first ever accounting of topographic change across the United States. Whiteriver, AZ USGS 1:24K Topographic Map Preview: Click on map above to begin viewing in our Map Viewer. The National Elevation Dataset (NED) and the Shuttle Radar Topography Mission (SRTM) data form a unique pair of seamless elevation datasets that can be used to detect and analyze 20th century topographic surface changes in the United States. OK There was a problem loading one or more map services. The USGS has developed a national inventory of significant topographic changes based on seamless multitemporal elevation data and land cover data. Geocortex Viewer for HTML5 conforms to WCAG 2.0 level AA (international & United States), as part of Latitude Geographics' Geocortex Essentials technology for Esri's ArcGIS platform.
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