This digital terrain model represents historical elevations along the valley of the North Fork Toutle River upstream of its confluence with the Green River in Cowlitz and Skamania Counties, Washington. Most elevations were derived from U.S. Geological Survey 1:62,500 scale topographic quadrangle maps published from 1953 to 1958 that were derived from aerial photographs taken in 1951 and 1952. Elevations representing the bed of Spirit Lake, at the head of the valley, were derived from a bathymetric map based on survey data from 1974. Elevations are in units of meters and have been adjusted to the North American Vertical Datum of 1988.

The Digital Raster Graphic (DRG) is a raster image of a scanned USGS topographic map including the collar information, georeferenced to the UTM grid. This version of the Digital Raster Graphic (DRG) has been clipped to remove the collar (white border of the map) and has been reprojected to geographic coordinates.

The USGS Elevation Contours service from The National Map (TNM) consists of contours generated for the conterminous United States from 1- and 1/3 arc-second elevation data. Small scale contours derived from 1 arc-second data are displayed at scales ranging from 1:577K to 1:72K in The National Map viewer. Contour intervals are 100 foot between 1:577K and 1:144K, and 50 foot at 1:72K. Large scale contours derived from 1/3 arc-second data are displayed at 1:50K (and larger). Large scale contour intervals are variable across the United States depending on complexity of topography. The National Map viewer allows free downloads of public domain contour data in either Esri File Geodatabase or Shapefile formats. The 3D Elevation Program (3DEP) provides elevation data for The National Map and basic elevation information for earth science studies and mapping applications. Scientists and resource managers use elevation data for global change research, hydrologic modeling, resource monitoring, mapping and visualization, and many other applications. For additional information on 3DEP, go to http://nationalmap.gov/3DEP/.

The color shaded relief map of the conterminous U.S. was created from 15 arc-second digital elevation model (DEM) data. The data set traces its origins back to the early 1960's when .01 inch scans of 1:250,000 USGS topographic sheets were produced by the Defense Mapping Agency and converted to 3 second data by the USGS National Cartographic Information Center. The 15 second grid cell data (Michael Webring, written communication) used in this report dates from the mid-1980's with occasional local and regional updates. The 3 second grid nodes were averaged with a 6x6 operator and decimated to 15 second grid cells which is about the resolution of the original .01 inch data set. The 3 second data is available as 950 separate 1x1 degree quadrangles from the USGS EROS Data Center.

Additional information available at "http://pubs.usgs.gov/of/of99-011/1readme.html"

[Summary provided by the USGS.]

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The Vegetation/Ecosystem Modeling and Analysis Project (VEMAP) is an ongoing multiinstitutional, international effort addressing the response of biogeography and biogeochemistry to environmental variability in climate and other drivers in both space and time domains. The objectives of VEMAP are the intercomparison of biogeochemistry models and vegetationtype distribution models (biogeography models) and determination of their sensitivity to changing climate, elevated atmospheric carbon dioxide concentrations, and other sources of altered forcing. The VEMAP data set includes three georeferencing and three cell area variables. Data Citation: This data set should be cited as follows: Kittel, T. G. F., N. A. Rosenbloom, T. H. Painter, D. S. Schimel, H. H. Fisher, A. Grimsdell, VEMAP Participants, C. Daly, and E. R. Hunt, Jr. 2002. VEMAP Phase I Database, revised. Available on-line from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

Culminating more than four years of processing data, NASA and the National Geospatial-Intelligence Agency (NGA) have completed Earth's most extensive global topographic map. The mission is a collaboration among NASA, NGA, and the German and Italian space agencies. For 11 days in February 2000, the space shuttle Endeavour conducted the Shuttle Radar Topography Mission (SRTM) using C-Band and X-Band interferometric synthetic aperture radars to acquire topographic data over 80% of the Earth's land mass, creating the first-ever near-global data set of land elevations. This data was used to produce topographic maps (digital elevation maps) 30 times as precise as the best global maps used today. The SRTM system gathered data at the rate of 40,000 per minute over land. They reveal for the first time large, detailed swaths of Earth's topography previously obscured by persistent cloudiness. The data will benefit scientists, engineers, government agencies and the public with an ever-growing array of uses. The SRTM radar system mapped Earth from 56 degrees south to 60 degrees north of the equator. The resolution of the publicly available data is three arc-seconds (1/1,200th of a degree of latitude and longitude, about 295 feet, at Earth's equator). The final data release covers Australia and New Zealand in unprecedented uniform detail. It also covers more than 1,000 islands comprising much of Polynesia and Melanesia in the South Pacific, as well as islands in the South Indian and Atlantic oceans. SRTM data are being used for applications ranging from land use planning to "virtual" Earth exploration. Currently, the mission's homepage "http://www.jpl.nasa.gov/srtm" provides direct access to recently obtained earth images. The Shuttle Radar Topography Mission C-band data for North America and South America are available to the public. A list of complete public data set is available at "http://www2.jpl.nasa.gov/srtm/dataprod.htm" The data specifications are within the following parameters: 30-meter X 30-meter spatial sampling with 16 meter absolute vertical height accuracy, 10-meter relative vertical height accuracy, and 20-meter absolute horizontal circular accuracy. From the JPL Mission Products Summary, "http://www.jpl.nasa.gov/srtm/dataprelimdescriptions.html". The primary products of the SRTM mission are the digital elevation maps of most of the Earth's surface. Visualized images of these maps are available for viewing online. Below you will find descriptions of the types of images that are being generated: Radar Image Radar Image with Color as Height Radar Image with Color Wrapped Fringes -Shaded Relief Perspective View with B/W Radar Image Overlaid Perspective View with Radar Image Overlaid, Color as Height Perspective View of Shaded Relief Perspective View with Landsat or other Image Overlaid Contour Map - B/W with Contour Lines Stereo Pair Anaglypgh The SRTM radar contained two types of antenna panels, C-band and X-band. The near-global topographic maps of Earth called Digital Elevation Models (DEMs) are made from the C-band radar data. These data were processed at the Jet Propulsion Laboratory and are being distributed through the United States Geological Survey's EROS Data Center. Data from the X-band radar are used to create slightly higher resolution DEMs but without the global coverage of the C-band radar. The SRTM X-band radar data are being processed and distributed by the German Aerospace Center, DLR.

The dataset is a digital elevation model (DEM), in GeoTiff format, of the bathymetry of Gillham Lake, Sevier County, Arkansas. The extent of the DEM represents the area encompassing the extent of the aerial Light Detection And Ranging (LiDAR) data used in the project. Horizontal and vertical units are expressed in meters. The DEM was derived from an LAS dataset (an industry-standard binary format for storing aerial LiDAR data) created from point datasets stored in “Gillham2018_gdb”. The point datasets include aerial LiDAR data from a survey conducted in 2016 by the National Resources Conservation Service (U.S. Geological Survey, 2017), point data from digitized historical topographic maps, and bathymetric data from a survey conducted in June 2018 by the Lower Mississippi-Gulf Water Science Center of the U.S. Geological Survey (USGS) using methodologies for single and multi-beam sonar surveys similar to those described by Wilson and Richards (2006) and Richards and Huizinga (20 ...

This is a tiled collection of the 3D Elevation Program (3DEP) and is one meter resolution. The 3DEP data holdings serve as the elevation layer of The National Map, and provide foundational elevation information for earth science studies and mapping applications in the United States. Scientists and resource managers use 3DEP data for hydrologic modeling, resource monitoring, mapping and visualization, and many other applications. The elevations in this DEM represent the topographic bare-earth surface. USGS standard one-meter DEMs are produced exclusively from high resolution light detection and ranging (lidar) source data of one-meter or higher resolution. One-meter DEM surfaces are seamless within collection projects, but, not necessarily seamless across projects. The spatial reference used for tiles of the one-meter DEM within the conterminous United States (CONUS) is Universal Transverse Mercator (UTM) in units of meters, and in conformance with the North American Datum of 1983 (NAD83). All bare earth elevation values are in meters and are referenced to the North American Vertical Datum of 1988 (NAVD88). Each tile is distributed in the UTM Zone in which it lies. If a tile crosses two UTM zones, it is delivered in both zones. The one-meter DEM is the highest resolution standard DEM offered in the 3DEP product suite. Other 3DEP products are nationally seamless DEMs in resolutions of 1/3, 1, and 2 arc seconds. These seamless DEMs were referred to as the National Elevation Dataset (NED) from about 2000 through 2015 at which time they became the seamless DEM layers under the 3DEP program and the NED name and system were retired. Other 3DEP products include five-meter DEMs in Alaska as well as various source datasets including the lidar point cloud and interferometric synthetic aperture radar (Ifsar) digital surface models and intensity images. All 3DEP products are public domain.

A 10-meter resolution land surface digital elevation model (DEM) for the island of Oahu in Hawaii from U.S. Geological Survey (USGS) 1/3 arc-second DEM quadrangles. For a grayscale hillshade image layer of this dataset, see "hi_usgs_oahu_dem10m_hillshade" and "hi_usgs_all_dem10m_hillshade" in the distribution links listed in the metadata. acknowledgement=The Pacific Islands Ocean Observing System (PacIOOS) is funded through the National Oceanic and Atmospheric Administration (NOAA) as a Regional Association within the U.S. Integrated Ocean Observing System (IOOS). PacIOOS is coordinated by the University of Hawaii School of Ocean and Earth Science and Technology (SOEST). cdm_data_type=Grid comment=These data are provided by USGS and subsequently distributed via THREDDS Data Server (TDS) and ERDDAP by PacIOOS. Conventions=CF-1.6, ACDD-1.3 date_metadata_modified=2023-01-20 drawLandMask=off Easternmost_Easting=-157.6486640799658 geospatial_bounds=POLYGON ((21.254748 -158.280969, 21.712459 -158.280969, 21.712459 -157.648618, 21.254748 -157.648618, 21.254748 -158.280969)) geospatial_bounds_crs=EPSG:4326 geospatial_lat_max=21.712412752206696 geospatial_lat_min=21.254794138987258 geospatial_lat_resolution=9.259785779430149E-5 geospatial_lat_units=degrees_north geospatial_lon_max=-157.6486640799658 geospatial_lon_min=-158.28092225298528 geospatial_lon_resolution=9.259785779429784E-5 geospatial_lon_units=degrees_east history=2015-05-11T00:00:00Z PacIOOS obtained ArcInfo Binary Grids from The National Map Viewer of USGS then mosaicked and converted to NetCDF format and EPSG:4326 spatial reference system. id=usgs_dem_10m_oahu infoUrl=https://www.usgs.gov/core-science-systems/national-geospatial-program/national-map institution=U.S. Geological Survey (USGS) instrument=Not Applicable > Not Applicable instrument_vocabulary=GCMD Instrument Keywords ISO_Topic_Categories=elevation keywords_vocabulary=GCMD Science Keywords locations=Continent > North America > United States Of America > Hawaii, Ocean > Pacific Ocean > Central Pacific Ocean > Hawaiian Islands > Oahu locations_vocabulary=GCMD Location Keywords metadata_link=https://www.pacioos.hawaii.edu/metadata/usgs_dem_10m_oahu.html naming_authority=org.pacioos Northernmost_Northing=21.712412752206696 platform=Models/Analyses > > DEM > Digital Elevation Model platform_vocabulary=GCMD Platform Keywords program=Pacific Islands Ocean Observing System (PacIOOS) project=Pacific Islands Ocean Observing System (PacIOOS) references=https://www.pacioos.hawaii.edu/metadata/hi_usgs_oahu_dem10m_hillshade.html; https://www.pacioos.hawaii.edu/metadata/hi_usgs_all_dem10m_hillshade.html source=USGS 1/3 arc-second DEM quadrangles sourceUrl=https://pae-paha.pacioos.hawaii.edu/thredds/dodsC/usgs_dem_10m_oahu Southernmost_Northing=21.254794138987258 standard_name_vocabulary=CF Standard Name Table v39 time_coverage_duration=P0D time_coverage_resolution=P0D Westernmost_Easting=-158.28092225298528

Download In State Plane Projection Here The 2017 Digital Terrain Model (DTM) is a 2 foot pixel resolution raster in Erdas IMG format. This was created using the ground (class = 2) lidar points and incorporating the breaklines. The DTMs were developed using LiDAR data. LiDAR is an acronym for LIght Detection And Ranging. Light detection and ranging is the science of using a laser to measure distances to specific points. A specially equipped airplane with positioning tools and LiDAR technology was used to measure the distance to the surface of the earth to determine ground elevation. The classified points were developed using data collected in April to May 2017. The LiDAR points, specialized software, and technology provide the ability to create a high precision three-dimensional digital elevation and/or terrain models (DEM/DTM). The use of LiDAR significantly reduces the cost for developing this information. The DTMs are intended to correspond to the orthometric heights of the bare surface of the county (no buildings or vegetation cover). DTM data is used by county agencies to study drainage issues such as flooding and erosion; contour generation; slope and aspect; and hill shade images. This dataset was compiled to meet the American Society for Photogrammetry and Remote Sensing (ASPRS) Accuracy Standards for Large-Scale Maps, CLASS 1 map accuracy. The U.S. Army Corps of Engineers Engineering and Design Manual for Photogrammetric Production recommends that data intended for this usage scale be used for any of the following purposes: route location, preliminary alignment and design, preliminary project planning, hydraulic sections, rough earthwork estimates, or high-gradient terrain / low unit cost earthwork excavation estimates. The manual does not recommend that these data be used for final design, excavation and grading plans, earthwork computations for bid estimates or contract measurement and payment. This dataset does not take the place of an on-site survey for design, construction or regulatory purposes.

A Digital Raster Graphic (DRG) is a scanned image of a U.S. Geological Survey (USGS) topographic map. An unclipped scanned image includes all marginal information, while a clipped or seamless scanned image clips off the collar information. DRGs may be used as a source or background layer in a geographic information system, as a means to perform quality assurance on other digital products, and as a source for the collection and revision of digital line graph data. The DRGs also can be merged with other digital data (e.g., digital elevation model or digital orthophotoquad data), to produce a hybrid digital file. The output resolution of a DRG varies from 250 to 500 dots per inch. The horizontal positional accuracy of the DRG matches the accuracy of the published source map. To be consistent with other USGS digital data, the image is cast on the UTM projection, and therefore, will not always be consistent with the credit note on the image collar. Only the area inside the map neatline is georeferenced, so minor distortion of the text may occur in the map collar. Refer to the scanned map collar or online Map List for the currentness of the DRG.

A 10-meter resolution land surface digital elevation model (DEM) for the islands of Palau from U.S. Geological Survey (USGS) 1/3 arc-second DEM quadrangles. For a grayscale hillshade image layer of this dataset, see "pw_usgs_all_dem10m_hillshade" in the distribution links listed in the metadata. acknowledgement=The Pacific Islands Ocean Observing System (PacIOOS) is funded through the National Oceanic and Atmospheric Administration (NOAA) as a Regional Association within the U.S. Integrated Ocean Observing System (IOOS). PacIOOS is coordinated by the University of Hawaii School of Ocean and Earth Science and Technology (SOEST). cdm_data_type=Grid comment=These data are provided by USGS and subsequently distributed via THREDDS Data Server (TDS) and ERDDAP by PacIOOS. Conventions=CF-1.6, ACDD-1.3 date_metadata_modified=2023-01-20 drawLandMask=off Easternmost_Easting=134.64967501368815 geospatial_bounds=POLYGON ((6.874626 134.096848, 7.754260 134.096848, 7.754260 134.693147, 6.874626 134.693147, 6.874626 134.096848)) geospatial_bounds_crs=EPSG:4326 geospatial_lat_max=7.754213715821437 geospatial_lat_min=6.874765028140425 geospatial_lat_resolution=9.25930393431261E-5 geospatial_lat_units=degrees_north geospatial_lon_max=134.64967501368815 geospatial_lon_min=134.09689456880972 geospatial_lon_resolution=9.259303934312171E-5 geospatial_lon_units=degrees_east history=2015-05-11T00:00:00Z PacIOOS obtained ArcInfo Binary Grids from The National Map Viewer of USGS then mosaicked and converted to NetCDF format and EPSG:4326 spatial reference system. id=usgs_dem_10m_palau infoUrl=https://www.usgs.gov/core-science-systems/national-geospatial-program/national-map institution=U.S. Geological Survey (USGS) instrument=Not Applicable > Not Applicable instrument_vocabulary=GCMD Instrument Keywords ISO_Topic_Categories=elevation keywords_vocabulary=GCMD Science Keywords locations=Ocean > Pacific Ocean > Western Pacific Ocean > Micronesia > Palau locations_vocabulary=GCMD Location Keywords metadata_link=https://www.pacioos.hawaii.edu/metadata/usgs_dem_10m_palau.html naming_authority=org.pacioos Northernmost_Northing=7.754213715821437 platform=Models/Analyses > > DEM > Digital Elevation Model platform_vocabulary=GCMD Platform Keywords program=Pacific Islands Ocean Observing System (PacIOOS) project=Pacific Islands Ocean Observing System (PacIOOS) references=https://www.pacioos.hawaii.edu/metadata/pw_usgs_all_dem10m_hillshade.html source=USGS 1/3 arc-second DEM quadrangles sourceUrl=https://pae-paha.pacioos.hawaii.edu/thredds/dodsC/usgs_dem_10m_palau Southernmost_Northing=6.874765028140425 standard_name_vocabulary=CF Standard Name Table v39 time_coverage_duration=P0D time_coverage_resolution=P0D Westernmost_Easting=134.09689456880972

This data set contains up to nine types of digital elevation data: 1-1 degree blocks, 2-1 degree x 3 degree mosaic of elevation (latitude/longitude coordinate system), 3-1 degree x 3 degree mosaic of slope, 4-1 degree x 3 degree mosaic of aspect (latitude/longitude coordinate system), 5-1 degree x 3 degree mosaic of filtered elevation (5 x 5 filter), 6-1 degree x 3 degree mosaic of elevation (UTM registered), 7-1 degree x 3 degree mosaic of slope (UTM registered), 8-1 degree x 3 degree mosaic of aspect (UTM registered), 9-1 degree x 3 degree mosaic of shaded relief (latitude/longitude coordinate system). Data coverage is from 1982 to present with work ongoing. Data source is 1:250,000 scale Defense Mapping Agency Digital Terrain Series. The data set currently contains 966 records with estimated growth of 5-15 records per year. Storage required varies by selection on area size. Data are available on: 9-track, 800 bpi, 1600 bpi, 6250 bpi, unlabeled, unblocked, or BCD tape. Subsets on the main file and custom formats as well as limited documentation is available.

    Data is organized by 7 1/2 ' or 15 ' quads. This data is intended to be used
    for land cover analysis, wildlife refuge studies, drainage analysis, and land
    use planning.

This is the seamless 3DEP DEM dataset for the U.S. with full coverage of the 48 conterminous states, Hawaii, and U.S. territories. Alaska coverage is partially available now and is being expanded to statewide coverage as part of the Alaska Mapping Initiative. Ground spacing is approximately 10 meters north/south, but variable east/west due to convergence of meridians with latitude. Spatial metadata dataset is ingested as a separate asset USGS_3DEP_10m_metadata. The 1m dataset is ingested as USGS_3DEP_1m. Dataset uploaded by Farmers Business Network.

Landslide susceptibility maps are essential tools in infrastructure planning, hazard mitigation, and risk reduction. Susceptibility maps trained in one area have been found to be unreliable when applied to different areas (Woodard et al., 2023). This limitation leads to the need for a national map that is higher resolution and rigorous, but simple enough to be applied to diverse terrains and landslide types. The susceptibility maps presented here cover the conterminous United States (CONUS), Alaska (AK), Hawaii (HI), and Puerto Rico (PR) with a resolution of 90-m. Other United States (U.S.) territories were not considered due to insufficient landslide and digital elevation data. We also provide information on the proportion of susceptible terrain as well as the density (landslides per square kilometer) of documented landslides within susceptible terrain for each U.S. county. To generate the susceptibility maps we used 1/3 arc-second digital elevation models (DEMs) (U.S. Geological Survey, 2019) to calculate slope and 100-m relief, 613,724 unique landslides from our national landslide inventory compilation (Belair et al., 2022) to train the models and compute U.S. county aggregated susceptibility information, and high-performance computing resources to train the models (Falgout and Gordon, 2023). We present two slope-relief threshold models: (1) a linear regression model weighted by landslide density of each ecoregion (Wiken et al., 2011), and (2) a quantile nonlinear regression model fitted to the 10th quantile of the data. We (1) removed extraneous landslide data, (2) averaged 50 model runs, and then (3) down-sampled the maps from 10-m to 90-m resolution to account for uncertainty in the DEM and landslide position. The nonlinear model (n10) performs better under most topographic conditions and optimally balances our priorities of capturing observed landslides (98.9%) while minimizing area covered by susceptible terrain (44.6%). The weighted linear model (lw) captures slightly fewer landslides (98.8%) and has slightly less susceptible terrain (43.1%). The values of both maps represent the number of susceptible 10-m cells within each 90-m cell after down-sampling and can range from 0 to 81. While landslides are possible within any cells containing susceptible terrain, those with the highest concentration (or cell value) capture the majority of landslides, thus representing higher susceptibility areas. The susceptibility maps were then used to determine the total area of landslide susceptible terrain (square kilometers) for each U.S. county. The national landslide inventory compilation was used to determine the number of documented landslides within susceptible terrain for each county. This information was then used to calculate the proportion of susceptible terrain and the density of documented landslides within susceptible terrain for each county in the United States. This information is provided in tabular format, with columns corresponding to the information discussed above, and each row corresponding to a U.S. county. Further information about this analysis can be found in an interpretive publication (Mirus et al., 2024). This data release includes: (1) weighted linear susceptibility maps (lw_susc.zip), (2) quantile nonlinear susceptibility maps (n10_susc.zip), (3) landslide data used to develop the models (landslides.csv), (4) county aggregated susceptibility information (county_analysis.csv), (5) readme and analysis files, and (6) metadata. References Cited Belair, G. M., Jones, E. S., Slaughter, S. L., and Mirus, B. B., 2022, Landslide Inventories across the United States version 2: U.S. Geological Survey data release, https://doi.org/10.5066/P9FZUX6N Falgout, J. T., and Gordon, J., 2023, USGS Advanced Research Computing, USGS Yeti Supercomputer: U.S. Geological Survey, https://doi.org/10.5066/F7D798MJ Mirus, B. B., Belair, G. M., Wood, N. J., Jones, J. M., and Martinez, S. M., 2024, Parsimonious high-resolution landslide susceptibility modeling at continental scales, AGU Advances, https://doi.org/10.1029/2024AV001214 U.S. Geological Survey, 2019, 3D Elevation Program (3DEP) USGS 1/3 arc-second DEM [Data set], Retrieved from https://www.usgs.gov/3d-elevation-program/about-3dep-products-services Wiken, E., Nava, F. J., and Griffith, G., 2011, North American Terrestrial Ecoregions - Level III [Data set], Montreal, Canada: Commission for Environmental Cooperation, Retrieved from https://www.epa.gov/eco-research/level-iii-and-iv-ecoregions-continental-united-states Woodard, J. B., Mirus, B. B., Crawford, M. M., Or, D., Leshchinsky, B. A., Allstadt, K. E., and Wood, N. J., 2023, Mapping Landslide Susceptibility Over Large Regions With Limited Data, Journal of Geophysical Research: Earth Surface, 128(5), e2022JF006810, https://doi.org/10.1029/2022JF006810

The dataset is a digital elevation model (DEM) of the bathymetry of Norfork Lake, Arkansas-Missouri, below a pool elevation of 580 ft above the North American Vertical Datum of 1988 (NAVD88). The DEM was derived from a terrain (digital terrain model, or DTM) created from a feature dataset of point (XYZ) data collected during an aerial LiDAR survey conducted in March, 2008, and a bathymetric survey conducted in September-October, 2015. References: Lee, 2013, Estimation of reservoir storage capacity using multibeam sonar and terrestrial LiDAR, Randy Poynter Lake, Rockdale County, Georgia, 2012: U.S. Geological Survey Scientific Investigations Map 3265, 1 sheet, https://pubs.usgs.gov/sim/3265/; Huizinga, 2016, Bathymetric and velocimetric surveys at highway bridges crossing the Missouri River near Kansas City, Missouri, June 2–4, 2015: U.S. Geological Survey Scientific Investigations Report 2016–5061, 93 p., http://dx.doi.org/10.3133/sir20165061.

December 1995, June 2001

GTOPO30 is a global digital elevation model (DEM) with a horizontal grid spacing of 30-arc seconds (0.008333333333333 degrees or approximately 1 kilometer), resulting in a DEM having dimensions of 21,600 rows and 43,200 columns. The horizontal coordinate system is decimal degrees of latitude and longitude referenced to World Geodetic System 84 (WGS84). The vertical units represent elevation in meters above mean sea level. The elevation values range from -407 to 8,752 meters. In the DEM, ocean areas have been masked as no data and have been assigned a value of -9999. Lowland coastal areas have an elevation of at least 1 meter (so in the event that a user reassigns the ocean value from -9999 to 0 the land boundary portrayal will be maintained). Small islands in the ocean less than approximately 1 square kilometer are not represented.

GTOPO30 was derived from several raster and vector sources of topographic information. These sources include: Digital Terrain Elevation Data, Digital Chart of the World, USGS 1-degree Digital Elevation Models, Army Map Service 1:1,000,000-scale Maps, International 1:1,000,000-scale Map of the World, Peru 1:1,000,000-scale Map, New Zealand DEM, and Antarctic digital Database.

GTOPO30 was developed to meet the needs of the geospatial data user community for regional and continental scale topographic data. The data are suitable for many regional and continental applications, such as climate modeling, continental-scale land cover mapping, extraction ofdrainage features for hydrologic modeling and geometric and atmospheric correction of medium and coarse resolution satellite image data.

An example of a recent application derived from GTOPO30 is HYDRO1k, a geographic database (at a resolution of 1 km) developed to provide comprehensive and consistent global coverage of topographically derived data sets, including streams, drainage basins, and ancillary layers . HYDRO1k provides a suite of geo-referenced data sets, both raster and vector, which will be of value for all users who need to organize, evaluate, or process hydrologic information on a continental scale. The raster data sets are the hydrologically correct DEM, derived flow directions, flow accumulations, slope, aspect, and a compound topographic (wetness) index. The derived streamlines and basins are distributed as vector data sets.

GTOPO30 was developed through a collaborative effort led by staff at the U.S. Geological Survey's EROS EDC. The following organizations participated by contributing funding or source data: the National Aeronautics and Space Administration (NASA), the United Nations Environment Programme/Global Resource Information Database (UNEP/GRID), the U.S. Agency for International Development (USAID), the Instituto Nacional de Estadistica Geografica e Informatica (INEGI) of Mexico, the Geographical Survey Institute (GSI) of Japan, Manaaki Whenua Landcare Research of New Zealand, and the Scientific Committee on Antarctic Research (SCAR).

The U.S. Geological Survey (USGS) Aerial Photography data set includes over 2.5 million film transparencies. Beginning in 1937, photographs were acquired for mapping purposes at different altitudes using various focal lengths and film types. The resultant black-and-white photographs contain less than 5 percent cloud cover and were acquired under rigid quality control and project specifications (e.g., stereo coverage, continuous area coverage of map or administrative units). Prior to the initiation of the National High Altitude Photography (NHAP) program in 1980, the USGS photography collection was one of the major sources of aerial photographs used for mapping the United States. Since 1980, the USGS has acquired photographs over project areas that require photographs at a larger scale than the photographs in the NHAP and National Aerial Photography Program collections.

One mosaic of 273 map sheets and one additional map sheet: 1. Index to maps of India and Pakistan. Scale of 1:250 000. Date of publication: 1966. 2. India and Pakistan: Series U502 : NC-43-03 : Calicut. Scale of 1:250 000. Date of publication: 1959. 3. India and Pakistan: Series U502 : NC-43-04 : Erode. Scale of 1:250 000. Date of publication: 1959. 4. India and Pakistan: Series U502 : NC-43-07 : Coimbatore. Scale of 1:250 000. Date of publication: 1959. 5. India and Pakistan: Series U502 : NC-43-08 : Dindigul. Scale of 1:250 000. Date of publication: 1959. 6. India and Pakistan: Series U502 : NC-43-11 : Alleppey. Scale of 1:250 000. Date of publication: 1955. 7. India and Pakistan: Series U502 : NC-43-12 : Rajapalaiyam. Scale of 1:250 000. Date of publication: 1955. 8. India and Pakistan: Series U502 : NC-43-16 : Trivandrum. Scale of 1:250 000. Date of publication: 1959. 9. India and Pakistan: Series U502 : NC-44-01 : Salem. Scale of 1:250 000. Date of publication: 1959. 10. India and Pakistan: Series U502 : NC-44-05 : Tiruchirappalli. Scale of 1:250 000. Date of publication: 1955. 11. India and Pakistan: Series U502 : NC-44-09 : Madura. Scale of 1:250 000. Date of publication: 1955. 12. India and Pakistan: Series U502 : NC-44-13 : Cuddalore. Scale of 1:250 000. Date of publication: 1959. 13. India and Pakistan: Series U502 : NC-44-13 : Tuticorin. Scale of 1:250 000. Date of publication: 1959. 14. India and Pakistan: Series U502 : ND-43-02 : Belgaum. Scale of 1:250 000. Date of publication: 1960. 15. India and Pakistan: Series U502 : ND-43-03 : Hubli. Scale of 1:250 000. Date of publication: 1960. 16. India and Pakistan: Series U502 : ND-43-04 : Bellary. Scale of 1:250 000. Date of publication: 1961. 17. India and Pakistan: Series U502 : ND-43-06 : Karwar. Scale of 1:250 000. Date of publication: 1960. 18. India and Pakistan: Series U502 : ND-43-07 : Davangere. Scale of 1:250 000. Date of publication: 1958. 19. India and Pakistan: Series U502 : ND-43-08 : Anantapur. Scale of 1:250 000. Date of publication: 1961. 20. India and Pakistan: Series U502 : ND-43-11 : Shimoga. Scale of 1:250 000. Date of publication: 1959. 21. India and Pakistan: Series U502 : ND-43-12 : Tumkur. Scale of 1:250 000. Date of publication: 1961. 22. India and Pakistan: Series U502 : ND-43-15 : Mangalore. Scale of 1:250 000. Date of publication: 1962. 23. India and Pakistan: Series U502 : ND-43-16 : Mysore. Scale of 1:250 000. Date of publication: 1959. 24. India and Pakistan: Series U502 : ND-44-01 : Kurnool. Scale of 1:250 000. Date of publication: 1956. 25. India and Pakistan: Series U502 : ND-44-02 : Chirala. Scale of 1:250 000. Date of publication: 1959. 26. India and Pakistan: Series U502 : ND-44-03 : Divi Point. Scale of 1:250 000. Date of publication: 1956. 27. India and Pakistan: Series U502 : ND-44-05 : Cuddapah. Scale of 1:250 000. Date of publication: 1956. 28. India and Pakistan: Series U502 : ND-44-06 : Nellore. Scale of 1:250 000. Date of publication: 1959. 29. India and Pakistan: Series U502 : ND-44-09 : Kolar. Scale of 1:250 000. Date of publication: 1960. 30. India and Pakistan: Series U502 : ND-44-10 : Madras. Scale of 1:250 000. Date of publication: 1957. 31. India and Pakistan: Series U502 : ND-44-13 : Bangalore. Scale of 1:250 000. Date of publication: 1959. 32. India and Pakistan: Series U502 : ND-44-14 : Conjeeveram. Scale of 1:250 000. Date of publication: 1956. 33. India and Pakistan: Series U502 : NE-43-01 : Kalyan. Scale of 1:250 000. Date of publication: 1963. 34. India and Pakistan: Series U502 : NE-43-02 : Ahmadnagar. Scale of 1:250 000. Date of publication: 1962. 35. India and Pakistan: Series U502 : NE-43-03 : Aurangabad. Scale of 1:250 000. Date of publication: 1960. 36. India and Pakistan: Series U502 : NE-43-04 : Nander. Scale of 1:250 000. Date of publication: 1960. 37. India and Pakistan: Series U502 : NE-43-05 : Bombay. Scale of 1:250 000. Date of publication: 1943. 38. India and Pakistan: Series U502 : NE-43-06 : Poona. Scale of 1:250 000. Date of publication: 1960. 39. India and Pakistan: Series U502 : NE-43-07 : Barsi. Scale of 1:250 000. Date of publication: 1960. 40. India and Pakistan: Series U502 : NE-43-08 : Latur. Scale of 1:250 000. Date of publication: 1961. 41. India and Pakistan: Series U502 : NE-43-09 : Khed. Scale of 1:250 000. Date of publication: 1960. 42. India and Pakistan: Series U502 : NE-43-10 : Satara. Scale of 1:250 000. Date of publication: 1960. 43. India and Pakistan: Series U502 : NE-43-11 : Sholapur. Scale of 1:250 000. Date of publication: 1963. 44. India and Pakistan: Series U502 : NE-43-12 : Gulbarga. Scale of 1:250 000. Date of publication: 1960. 45. India and Pakistan: Series U502 : NE-43-13 : Ratnagiri. Scale of 1:250 000. Date of publication: 1962. 46. India and Pakistan: Series U502 : NE-43-14 : Kolhapur. Scale of 1:250 000. Date of publication: 1962. 47. India and Pakistan: Series U502 : NE-43-15 : Bijap