The objective of Topographic Science within the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center Science and Applications Branch is to establish partnerships and conduct research and applications that facilitate the development and use of integrated national and global topographic datasets. Topographic Science includes research and applications that result in improved seamless topographic datasets, advanced elevation technology research, terrain visualization research, raster and vector technique development research, and development of internet presence. Integrated-science applications for mapping, national natural resource initiatives, hazards, and global change science are conducted with partners.
National Elevation Dataset (NED)
The NED is the primary elevation data product of the USGS. The NED is a seamless dataset with the best available raster elevation data of the conterminous United States, Alaska, Hawaii, and territorial islands. The NED is updated on a nominal two month cycle to integrate newly available, improved elevation source data. All NED data are public domain. The NED is derived from diverse source data that are processed to a common coordinate system and unit of vertical measure. NED data are distributed in geographic coordinates in units of decimal degrees, and in conformance with the North American Datum of 1983. All elevation values are in meters and, over the conterminous United States, are referenced to the North American Vertical Datum of 1988. The vertical reference will vary in other areas. NED data are available nationally (except for Alaska) at resolutions of 1 arc-second (~ 30m) and 1/3 arc-second (~ 10m), and in limited areas at 1/9 arc-second (~ 3m). In most of Alaska, only lower resolution source data are available. As a result, most NED data for Alaska are at 2-arc-second (~ 6m) grid spacing. Part of Alaska is available at the 1- and 1/3-arc-second resolution, and plans are in development for a significant improvement in elevation data coverage of the state. The NED serves as the elevation layer of The National Map, and provides basic elevation information for earth science studies and mapping applications in the United States. Scientists and resource managers use NED data for global change research, hydrologic modeling, resource monitoring, mapping and visualization, and many other applications.
Elevation Derivatives for National Applications (EDNA)
EDNA is a multi-layered database derived from a version of the NED, which has been hydrologically conditioned for improved hydrologic flow representation. The seamless EDNA database provides 30-meter resolution raster and vector data layers. Hydrologically conditioned elevation data, systematically and consistently processed to create hydrologic derivatives, can be useful in many topologically based visualization and investigative applications. Drainage areas upstream or downstream from any location can be accurately traced facilitating flood analysis investigations, pollution studies, and hydroelectric power generation projects.
Center for LIDAR Information Coordination and Knowledge
There has been increasing demand for research utilizing all information generated from light detection and ranging (lidar) remote sensing data and not just bare earth DEMs. While this technology has been a proven mapping tool, effective for generating bare earth DEMs, research on using the entire point cloud of this remote sensing data for scientific applications have been slowed by the high cost of collecting lidar, a steep learning curve on research and understanding involving utilizing the entire point cloud. The goal of CLICK is to facilitate data access, user coordination and education of lidar remote sensing for scientific needs.
The USGS has developed a national inventory of significant topographic changes based on seamless multi-temporal elevation data and land cover data. The 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. 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. The primary types of topographic changes resulting from human geomorphic activity include surface mining, road construction, urban development, dam construction, and landfills.
Topo - Bathy
Topobathymetric data (a “topobathy”) are a merged rendering of both topography (land elevation) and bathymetry (water depth) to provide a single product useful for inundation mapping and a variety of other applications. These data were developed using one topographic and two bathymetric datasets collected at different dates. Topography was obtained from the USGS NED. Bathymetry was provided by NOAA's GEOphysical DAta System (GEODAS). Northern Gulf of Mexico topobathy database development is currently being developed in collaboration with the USGS Coastal and Marine Geology Program.
The USGS and the National Geospatial-Intelligence Agency (NGA) have collaborated on the development of a notably enhanced global elevation model called the Global Multi-resolution Terrain Elevation Data (GMTED2010), which has replaced GTOPO30 as the elevation dataset of choice for global and continental scale applications. The new model has been generated at three separate resolutions of 30 arc-seconds, 15 arc-seconds, and 7.5 arc-seconds. An additional advantage of this new multi-resolution global model is that seven new raster elevation products are available at each resolution. The new elevation products have been produced using the following aggregation methods: minimum elevation, maximum elevation, mean elevation, median elevation, standard deviation of elevation, systematic subsample, and breakline emphasis. The primary source dataset for the new global model is the 1 arc-second void-filled SRTM data.
GTOPO30 is a global DEM with a horizontal grid spacing of 30 arc seconds (approximately 1 kilometer). GTOPO30 was derived from several raster and vector sources of topographic information. For easier distribution, GTOPO30 has been divided into tiles. Detailed information on the characteristics of GTOPO30 including the data distribution format, the data sources, production methods, accuracy, and hints for users, is found in the GTOPO30 README file.