Significant Topographic Changes in the United States
The USGS has developed a national inventory of significant topographic changes based on seamless multitemporal elevation data and land cover data. 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.
Science
Ranking Features Based on Magnitude of Change
Each of the polygons in the topographic change inventory has numerous attributes associated with it. These attributes allow a ranking of features based on the magnitude of change, as measured by polygon descriptors (area and volume) and changes in terrain parameters (elevation, relief, slope, aspect). The ability to do such a ranking points out one of the advantages of producing spatially explicit...
Quadrangle Base Maps
Many resource managers and geospatial data users are familiar with the USGS 7.5-minute quadrangle map series. Also, much of the geospatial data managed by the USGS was originally produced in tiles corresponding to the 7.5-minute maps. The topographic map quadrangles are still commonly used as base maps for outlining data collection strategies and defining project boundaries. Thus, it is useful to...
1x1-Degree Tiles
Summary statistics were also accumulated on the basis of the 1x1-degree tiles used for data management and processing. A total of 500 tiles contain topographic change polygons (see figure below), which represents over 53 percent of the conterminous United States tiles.