Significant Topographic Changes in the United States
The detection of human geomorphic activity, as indicated by vertical changes to the land surface, is accomplished by comparing multitemporal elevation data. As such, multidate elevation data with matching characteristics over the large study area of the conterminous United States are required.
The National Elevation Dataset (NED) and the Shuttle Radar Topography Mission (SRTM) data form a unique pair of elevation datasets that can be used to detect, measure, and analyze 20th century topographic surface changes in the United States. Both the NED and the SRTM data have a nominal spatial resolution of 1 arc-second (about 30 meters), and each resource is managed as a seamless dataset for efficient access and manipulation.
Land Cover Data
The National Land Cover Dataset (NLCD) provided land cover information at a 30-meter resolution that matched the NED and SRTM data.