Continuous and optimized 3-arcsecond elevation model for the United States east coast (32-bit GeoTiff, geographic, NAD83)

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Frequently anticipated questions:

What does this data set describe?

Title:
Continuous and optimized 3-arcsecond elevation model for the United States east coast (32-bit GeoTiff, geographic, NAD83)
Abstract:
Investigations of coastal change and coastal resources often require continuous elevation profiles from the seafloor to coastal terrestrial landscapes. Differences in elevation data collection in the terrestrial and marine environments result in separate elevation products that may not share a vertical datum. This data release contains the compilation of multiple elevation products into a continuous digital elevation model at a resolution of 3-arcseconds (approximately 90 meters) from the terrestrial landscape to the seafloor for the contiguous U.S. and portions of Mexico and Canada, focused on the coastal interface. All datasets were converted to a consistent horizontal datum, the North American Datum of 1983, but the native vertical datum for each dataset was not adjusted. Artifacts in the source elevation products were identified visually and replaced with other available elevation products when possible, corrected using various spatial tools, or otherwise marked for future correction.
  1. How might this data set be cited?
    Befus, Kevin M., and Kroeger, Kevin D., 2017, Continuous and optimized 3-arcsecond elevation model for the United States east coast (32-bit GeoTiff, geographic, NAD83): data release DOI:10.5066/F7W37TGK, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details:
    The first link is to the publication landing page. The second link is to the page containing the data. And the final link is a direct link to download the data.
    This is part of the following larger work.

    Befus, Kevin M., and Kroeger, Kevin D., 2017, Continuous and optimized 3-arcsecond elevation model for United States east and west coasts: data release DOI:10.5066/F7W37TGK, U.S. Geological Survey, Reston, Virginia.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Befus, K.M., and Kroeger, K.D., 2017, Continuous and optimized 3-arcsecond elevation model for United States east and west coasts: U.S. Geological Survey data release, https://doi.org/10.5066/F7W37TGK.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -100.00167
    East_Bounding_Coordinate: -66.489167
    North_Bounding_Coordinate: 46.002255
    South_Bounding_Coordinate: 24.112255
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/57f2667ae4b0bc0bebfff906?name=east_cDEM_overview.png (PNG)
    Color image of terrain model for contiguous U.S. east coast marine coastlines and portions of Canada and Mexico. The source files are the 32-bit GeoTiff files associated with this data release.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2016
    Currentness_Reference:
    publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: raster digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference:
      Contiguous U.S. east coast areas and portions of Mexico and Canada.
      This is a Raster data set.
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 1.0. Longitudes are given to the nearest 1.0. Latitude and longitude values are specified in Decimal seconds. The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.2572221.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name:
      Variable. North American Vertical Datum of 1988 above an elevation of 0 m (source: NED). Bathymetric data sources had different vertical datums that were not adjusted prior to merging due to the relatively large grid cell size.
      Altitude_Resolution: 2
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    Elevation
    Elevation data (Source: Other)
    Value
    Elevation (Source: U.S. Geological Survey)
    Range of values
    Minimum:-3193.4
    Maximum:2155.4
    Units:Meters

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Kevin M. Befus
    • Kevin D. Kroeger
  2. Who also contributed to the data set?
    Please recognize the U.S. Geological Survey (USGS) as the source of this information.
  3. To whom should users address questions about the data?
    Kevin D. Kroeger
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2270 (voice)
    kkroeger@usgs.gov

Why was the data set created?

The purpose of this data release is to provide a new continuous elevation model of U.S. coastal environments from onshore to offshore for various coastal applications requiring a smooth coastal interface. This dataset was created to primarily supply a smooth coastal interface to inform groundwater models requiring continuous elevations from onshore to offshore. Alternative coastal elevation datasets either lack elevation data for both terrestrial topography and marine bathymetry, provide data for a specific region within the continental United States (i.e., not continuous for either the east or west coast), or contain sufficient artifacts from its creation to reduce the utility of the dataset for the purposes of providing constraints for coastal groundwater models. This data release contains the compilation of multiple elevation products into a continuous digital elevation model at a resolution of 3-arcseconds (approximately 90 meters) from the terrestrial landscape to the seafloor for the contiguous U.S. The terrestrial extent of the dataset was extended inland to roughly two eight digit hydrologic unit code (HUC8) watersheds beyond coastal waterbodies and estuaries. The seaward extent encompassed at least a 30 kilometers buffer of bathymetric data from the U.S. mainland.

How was the data set created?

  1. From what previous works were the data drawn?
    south_padre_tx_1-3_arc-second_navd88.asc (source 1 of 10)
    Grothe, P.G., Taylor, L.A., Eakins, B.W., Carignan, K.S., Friday, D.Z., and Love, M., 2012, South Padre Island, TX 1/3 arc-second NAVD 88 DEM: NOAA, NOAA National Geophysical Data Center Boulder, CO.

    Online Links:

    Other_Citation_Details:
    The vertical datum for the data is NAVD 88. The horizontal datum for the data is WGS 1984. The original cell-size is 1/3-arcsecond.
    Type_of_Source_Media: Raster
    Source_Contribution:
    Full dataset used to replace overlaping data in western_gom_crm_v1.
    cape_hatteras.asc (source 2 of 10)
    Taylor, L.A., Eakins, B.W., Carignan, K.S., Warnken, R.R., Schoolcraft, D.C., and Sharman, G.F., 2008, Cape Hatteras, NC 1/3 arc-second MHW DEM: NOAA, NOAA National Geophysical Data Center Boulder, CO.

    Online Links:

    Other_Citation_Details:
    The vertical datum for the data is the mean height of water (MHW). The horizontal datum for the data is WGS 1984. The original cell-size is 1/3-arcsecond. Original disclaimer: "THIS DATA IS NOT TO BE USED FOR NAVIGATION. Although these data are of high quality and useful for planning and modeling purposes, they do not necessarily reflect current conditions, nor do they depict data which is on a nautical chart. For navigation please refer to the NOS nautical chart series."
    Type_of_Source_Media: Raster
    Source_Contribution:
    The cape_hatteras data were used to replace se_atl_crm_v1 for an area outlined by a feature in DEM_artifacts.shp covering the upper Gulf of Maine in one feature south of Cape Hatteras, North Carolina.
    northern_gulf_coast_navd_88.grd (source 3 of 10)
    Love, M.R., Amante, C.J., Eakins, B.W., and Taylor, L.A., 2012, Northern Gulf Coast, LA/MS/FL/AL 1 arc-second NAVD 88 DEM: U.S. Dept. of Commerce, Boulder, CO.

    Online Links:

    Other_Citation_Details:
    The vertical datum for the data is NAVD 88. The horizontal datum for the data is WGS 1984. The original cell-size is 1-arcsecond. Original disclaimer: "THIS DATA IS NOT TO BE USED FOR NAVIGATION. Although these data are of high quality and useful for planning and modeling purposes, they do not necessarily reflect current conditions, nor do they depict data which is on a nautical chart. For navigation please refer to the NOS nautical chart series."
    Type_of_Source_Media: Raster
    Source_Contribution:
    Full dataset was used to replace overlapping data in central_gom_crm_v1 except for areas in Vdatum_NGulfCoast indicated with type=Replace in DEM_artifacts.shp.
    gom03_v1_0.tif (source 4 of 10)
    Twomey, E.R., and Signell, R.P., 2013, Construction of a 3-Arcsecond Digital Elevation Model for the Gulf of Maine: U.S. Geological Survey, Reston, Virginia.

    Online Links:

    Other_Citation_Details:
    The vertical datum for the data is NAVD 88. The horizontal datum for the data is NAD 1983. The original cell-size is 3-arcseconds. Original disclaimer: "THIS DATA IS NOT TO BE USED FOR NAVIGATION. Although these data are of high quality and useful for planning and modeling purposes, they do not necessarily reflect current conditions, nor do they depict data which is on a nautical chart. For navigation please refer to the NOS nautical chart series."
    Type_of_Source_Media: Raster
    Source_Contribution:
    The gom03_v1_0.tif data were used to replace ne_atl_crm_v1 for areas outlined by two features in DEM_artifacts.shp covering the upper Gulf of Maine in one feature and Martha's Vinyard and Nantucket Islands in the other.
    ne_atl_crm_v1.flt (source 5 of 10)
    NOAA National Centers for Environmental Information, unknown, US Coastal Relief Model - Northeast Atlantic: NOAA, National Oceanic and Atmospheric Administration National Centers for Environmental Information.

    Online Links:

    Other_Citation_Details:
    The vertical datum was not specified in the creation of the dataset from multiple bathymetric products with variable tidal datums. The large spatial resolution leads to cells that span elevations equivalient to the datum uncertainty introduced by the tidal range, making the specification of a vertical datum from a mean tidal position impossible. The horizontal datum is NAD 1983. The original cell size is 3-arcseconds. Original disclaimer: "THIS DATA IS NOT TO BE USED FOR NAVIGATION. Although these data are of high quality and useful for planning and modeling purposes, they do not necessarily reflect current conditions, nor do they depict data which is on a nautical chart. For navigation please refer to the NOS nautical chart series."
    Type_of_Source_Media: Raster
    Source_Contribution:
    All of the ne_atl_crm_v1 dataset was used for outlining artifacts in DEM_artfacts.shp. Only cells with an elevation equal to or less than 0 meters in the dataset datum were retained in the final topographic and bathymetry product. ne_atl_crm_v1 data were not directly used for areas with merging type artifacts or where other elevation data were used to replace ne_atl_crm_v1 data, outlined in DEM_artifacts.shp.
    se_atl_crm_v1.flt (source 6 of 10)
    NOAA National Centers for Environmental Information, unknown, US Coastal Relief Model - Southeast Atlantic: NOAA, National Oceanic and Atmospheric Administration National Centers for Environmental Information.

    Online Links:

    Other_Citation_Details:
    The vertical datum was not specified in the creation of the dataset from multiple bathymetric products with variable tidal datums. The large spatial resolution leads to cells that span elevations equivalient to the datum uncertainty introduced by the tidal range, making the specification of a vertical datum from a mean tidal position impossible. The horizontal datum is NAD 1983. The original cell size is 3-arcseconds. Original disclaimer: "THIS DATA IS NOT TO BE USED FOR NAVIGATION. Although these data are of high quality and useful for planning and modeling purposes, they do not necessarily reflect current conditions, nor do they depict data which is on a nautical chart. For navigation please refer to the NOS nautical chart series."
    Type_of_Source_Media: Raster
    Source_Contribution:
    All of the se_atl_crm_v1 dataset was used for outlining artifacts in DEM_artfacts.shp. Only cells with an elevation equal to or less than 0 meters in the dataset datum were retained in the final topographic and bathymetry product. se_atl_crm_v1 data were not directly used for areas with merging type artifacts or where other elevation data were used to replace se_atl_crm_v1 data, outlined in DEM_artifacts.shp.
    fl_east_gom_crm_v1.flt (source 7 of 10)
    NOAA National Centers for Environmental Information, unknown, US Coastal Relief Model - Florida and Eastern Gulf of Mexico: NOAA, National Oceanic and Atmospheric Administration National Centers for Environmental Information.

    Online Links:

    Other_Citation_Details:
    The vertical datum was not specified in the creation of the dataset from multiple bathymetric products with variable tidal datums. The large spatial resolution leads to cells that span elevations equivalient to the datum uncertainty introduced by the tidal range, making the specification of a vertical datum from a mean tidal position impossible. The horizontal datum is NAD 1983. The original cell size is 3-arcseconds. Original disclaimer: "THIS DATA IS NOT TO BE USED FOR NAVIGATION. Although these data are of high quality and useful for planning and modeling purposes, they do not necessarily reflect current conditions, nor do they depict data which is on a nautical chart. For navigation please refer to the NOS nautical chart series."
    Type_of_Source_Media: Raster
    Source_Contribution:
    No significant artifacts were found in fl_east_gom_crm_v1.flt. Only cells with an elevation equal to or less than 0 meters in the dataset datum were retained in the final topographic and bathymetry product.
    central_gom_crm_v1.flt (source 8 of 10)
    NOAA National Centers for Environmental Information, unknown, US Coastal Relief Model - Central Gulf of Mexico: NOAA, National Oceanic and Atmospheric Administration National Centers for Environmental Information.

    Online Links:

    Other_Citation_Details:
    The vertical datum was not specified in the creation of the dataset from multiple bathymetric products with variable tidal datums. The large spatial resolution leads to cells that span elevations equivalient to the datum uncertainty introduced by the tidal range, making the specification of a vertical datum from a mean tidal position impossible. The horizontal datum is NAD 1983. The original cell size is 3-arcseconds. Original disclaimer: "THIS DATA IS NOT TO BE USED FOR NAVIGATION. Although these data are of high quality and useful for planning and modeling purposes, they do not necessarily reflect current conditions, nor do they depict data which is on a nautical chart. For navigation please refer to the NOS nautical chart series."
    Type_of_Source_Media: Raster
    Source_Contribution:
    All of the central_gom_crm_v1 dataset was used for outlining artifacts in DEM_artfacts.shp. Only cells with an elevation equal to or less than 0 meters in the dataset datum were retained in the final topographic and bathymetry product. central_gom_crm_v1 data were not directly used for areas with merging type artifacts or where other elevation data were used to replace central_gom_crm_v1 data, outlined in DEM_artifacts.shp.
    western_gom_crm_v1.flt (source 9 of 10)
    NOAA National Centers for Environmental Information, unknown, US Coastal Relief Model - Western Gulf of Mexico: NOAA, National Oceanic and Atmospheric Administration National Centers for Environmental Information.

    Online Links:

    Other_Citation_Details:
    The vertical datum was not specified in the creation of the dataset from multiple bathymetric products with variable tidal datums. The large spatial resolution leads to cells that span elevations equivalient to the datum uncertainty introduced by the tidal range, making the specification of a vertical datum from a mean tidal position impossible. The horizontal datum is NAD 1983. The original cell size is 3-arcseconds. Original disclaimer: "THIS DATA IS NOT TO BE USED FOR NAVIGATION. Although these data are of high quality and useful for planning and modeling purposes, they do not necessarily reflect current conditions, nor do they depict data which is on a nautical chart. For navigation please refer to the NOS nautical chart series."
    Type_of_Source_Media: Raster
    Source_Contribution:
    All of the western_gom_crm_v1 dataset was used for outlining artifacts in DEM_artfacts.shp. Only cells with an elevation equal to or less than 0 meters in the dataset datum were retained in the final topographic and bathymetry product. western_gom_crm_v1 data were not directly used for areas with merging type artifacts or where other elevation data were used to replace western_gom_crm_v1 data, outlined in DEM_artifacts.shp.
    individual NED tiles (source 10 of 10)
    United States Geological Survey, 2013, U.S. Geological Survey national elevation dataset: U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: Raster
    Source_Contribution:
    1 by 1 degree seamless sections of the National Elevation Dataset (NED) were downloaded for U.S. coastal topography included within the potential area required for groundwater models of coastal areas. Elevations greater than 8 meters in the final product are all from NED data. Elevations between 8 and 0 meters may be NED values but the source depends on the availability of bathymetry for each grid cell.
  2. How were the data generated, processed, and modified?
    Date: 2016 (process 1 of 17)
    Step 1. Download CRM regions: Coastal Relief Model (CRM) data were downloaded in binary float format. This process step, and all subsequent process steps, were performed by the same person: Kevin M. Befus. Person who carried out this activity:
    Kevin M. Befus
    University of Wyoming
    University of Wyoming
    Laramie, WY
    USA

    307-766-2390 (voice)
    kbefus@uwyo.edu
    Contact_Instructions:
    Kevin is currently with the University of Wyoming as an Assistant Professor in the Civil and Architectural Engineering Department. His contact information has been updated to reflect this.
    Date: 2016 (process 2 of 17)
    Step 2. Download NED tiles: Individual 1-arcsecond National Elevation Dataset (NED) 1 degree by 1 degree tiles were downloaded within the extents of the CRM data. Each tile was downloaded and unzipped in Python 2.7.11 using the standard libraries zipfile and urllib2. For the U.S. east and west coast separately, the NED tiles were merged into a single NED DEM using the ArcGIS 10.3 Data Management\Raster\Raster Dataset\Mosaic to new raster tool to a 32-bit float GeoTiff using a mosaic method order of "LAST", an output cell size of 3-arcseconds, and all other options as defaults. No horizontal datum transformation was required for NED data. Data sources used in this process:
    • individual NED tiles
    Data sources produced in this process:
    • east_NED.tif
    Date: 2016 (process 3 of 17)
    Step 3. DEM inspection and artifact identification: Visual inspection of NED and CRM products revealed numerous artifacts associated with the creation of each dataset, primarily due to merging 1 degree x 1 degree subsets of the elevation data or due to interpolation in data-poor regions. Areas where grid merging created offsets in elevation were manually delineated with polygon features (DEM_artifacts.shp), indicating whether the merging problem was "terrestrial" (elevation greater than 0 meters), "offshore" (elevation of less than 0 meters), or "both". Other areas where data quality was questionable were also indicated with polygon features and assigned a type of "Merging", "Interp", or "Channel". Not all areas where artifacts were present were delineated. The primary focus of the artifact delineation was between -50 to 50 meters elevation. Only those interpolation artifacts that could be replaced by other data, were unavoidable/unfillable using other datasets, or were distinguishable from nearby bathymetry or topography were delineated and saved in DEM_artifacts.shp. Data sources produced in this process:
    • DEM_artifacts.shp
    Date: 2016 (process 4 of 17)
    Step 4. Supplementary data downloads: Additional elevation and bathymetry data were downloaded to replace the cells where the NED and CRM data contained artifacts or had no bathymetry data. These data were downloaded from online servers from the U.S. Geological Survey and the National Oceanic and Atmospheric Association (NOAA). The source names of this step correspond to the source identifier name and are the original downloaded datasets. Portions of these supplemental datasets that contained artifacts were also delineated in DEM_artifacts.shp. Data sources used in this process:
    • northern_gulf_coast_navd_88.grd
    • south_padre_tx_1-3_arc-second_navd88.asc
    • gom03_v1_0.tif
    Date: 2016 (process 5 of 17)
    Step 5. Northeast region correction: In ne_atl_crm_v1.flt, data-poor regions were replaced by a Gulf of Maine (GoME) topobathy product, gom03_v1_0.tif. The GoME data contained depression-type interpolation artifacts in nearshore areas that were first filled using the ArcGIS 10.3 Spatial Analyst\Hydrology\Fill tool with default settings to a temporary raster ("filled_GoME.tif"). Then, areas in northern GoME, Nantucket, and Martha's Vineyard (type='replace', DEM_artifacts.shp) were used as masks to extract the filled_GoME.tif values with ArcGIS 10.3 Spatial Analyst\Extraction\Extract by mask tool with default settings to a temporary raster ("GoME_extract.tif"). These extracted portions replaced the ne_atl_crm_v1.flt elevations using ArcGIS 10.3 Spatial Analyst\Map Algebra\Raster Calculator with the command "ne_atl_crm_vc.tif = Con(IsNull(GoME_extract.tif),ne_atl_crm_v1.flt,GoME_extract.tif)". The Raster Calculator command output extent was set to "Union of inputs" and the output coordinate system to WGS_1984 under Environmental Settings. GoME_extract.tif inherited the NAD_1983 coordinate system from gom03_v1_0.tif, but Raster Calculator applies a uniform coordinate system for raster operations that then returned the output to WGS_1984, not requiring a reprojection. Data sources used in this process:
    • ne_atl_crm_v1.flt
    • gom03_v1_0.tif
    Data sources produced in this process:
    • ne_atl_crm_vc.tif
    Date: 2016 (process 6 of 17)
    Step 6. Southeast region correction: A high-resolution topobathy product, cape_hatteras.asc, was available to replace an area offshore Cape Hatteras in se_atl_crm_v1.flt that contained a large (roughly 20 by 60 kilometers) interploation artifact. First, the dataset was converted from .asc to a temporary raster ("cape_hatteras.tif") using the ArcGIS 10.3 Conversion Tools\to Raster\ASCII to Raster tool with a FLOAT data type and the coordinate system (WGS 1984) selected as the Output Coordinates\Output coordinate system and cell size of 1-arcsecond under Environmental settings. Then, a feature outlining the artifact area (type='replace', DEM_artifacts.shp) was used as a mask to extract the cape_hatteras.tif values with ArcGIS 10.3 Spatial Analyst\Extraction\Extract by mask tool with default settings to a temporary raster ("cape_hatteras_extract.tif"). These extracted portions replaced the se_atl_crm_v1.flt elevations using ArcGIS 10.3 Spatial Analyst\Map Algebra\Raster Calculator with the command "se_atl_crm_vc.tif = Con(IsNull(cape_hatteras_extract.tif),se_atl_crm_v1.flt,cape_hatteras_extract.tif)". The Raster Calculator command output extent was set to "Union of inputs". Data sources used in this process:
    • se_atl_crm_v1.flt
    • cape_hatteras.asc
    Data sources produced in this process:
    • se_atl_crm_vc.tif
    Date: 2016 (process 7 of 17)
    Step 7. Central Gulf of Mexico region correction: A zone of significant artifacts in central_gom_crm_v1.flt was corrected by inserting northern_gulf_coast_navd_88.grd, a high resolution topobathy product using ArcGIS 10.3 Spatial Analyst\Map Algebra\Raster Calculator with the command "Vdatum_NGulfCoast.tif = Con(IsNull(northern_gulf_coast_navd_88.grd),central_gom_crm_v1.flt,northern_gulf_coast_navd_88.grd)". The Raster Calculator converts the output to the maximum cell size of the inputs by default, resulting in a downsampled elevation dataset to 3-arcseconds. The output extent of Raster Calculator was set to central_gom_crm_v1.flt under Environmental settings. However, northern_gulf_coast_navd_88.grd also contained internal artifacts both above and below 0 meters elevation. To ensure elevation artifacts from northern_gulf_coast_navd_88.grd did not affect the terrestrial topography in later steps, NED elevations were inserted into Vdatum_NGulfCoast.tif where artifacts were present. Following the same Extract by mask and Raster Calculator merging procedures in Step 5, cells in NED were extracted using features in DEM_artifacts.shp with type="replace" and inserted into Vdatum_NGulfCoast.tif with an output extent set to central_gom_crm_v1.flt. Data sources used in this process:
    • central_gom_crm_v1.flt
    • northern_gulf_coast_navd_88.grd
    Data sources produced in this process:
    • central_gom_crm_vc.tif
    Date: 2016 (process 8 of 17)
    Step 8. Western Gulf of Mexico region correction: A high-resolution topobathy product, south_padre_tx_1-3_arc-second_navd88.asc, was available to replace an area near South Padre Island, Texas in western_gom_crm_v1.flt that contained numerous artifacts. First, the dataset was converted from .asc to a temporary raster ("Vdatum_SPadreIsland.tif") using the ArcGIS 10.3 Conversion Tools\to Raster\ASCII to Raster tool with a FLOAT data type and the coordinate system (WGS 1984) selected as the Output Coordinates\Output coordinate system under Environmental settings. Following the Raster Calculator merging procedure in Step 5, Vdatum_SPadreIsland.tif replaced all coincident cells in western_gom_crm_v1.flt, using an output extent set to western_gom_crm_v1.flt. Data sources used in this process:
    • western_gom_crm_v1.flt
    • south_padre_tx_1-3_arc-second_navd88.asc
    Data sources produced in this process:
    • western_gom_crm_vc.tif
    Date: 2016 (process 9 of 17)
    Step 9. Bathymetry merge: After these region-specific corrections, the CRM region-based rasters were merged into two separate coastal datasets for the U.S. east and west coasts. The ArcGIS 10.3 Data Management\Raster\Raster Dataset\Mosaic to new raster tool was used to merge the CRM region-based rasters to temporary rasters ("east_CRM_WGS.tif","west_CRM_WGS.tif") with an output cell size of 3-arcseconds and a merge order of "FIRST". The order of the east coast regions was geographically in order along the coast from the northeast region to the western Gulf of Mexico. The order of the west coast regions was from south to north. The east_CRM_WGS.tif and west_CRM_WGS.tif rasters were transformed into the same horizontal datum as the NED data (NAD 1983 from WGS 1984) using the ArcGIS 10.3 Data Management\Projections and Transformations\Raster\Project Raster tool with a cell size of 1-arcsecond and otherwise default values. Data sources used in this process:
    • western_gom_crm_vc.tif
    • central_gom_crm_vc.tif
    • ne_atl_crm_vc.tif
    • se_atl_crm_vc.tif
    • fl_east_gom_crm_v1.flt
    Data sources produced in this process:
    • east_CRM_NAD.tif
    Date: 2016 (process 10 of 17)
    Step 10. Correct CRM merging: The final step for the CRM bathymetry data was to smooth any merging artifacts present in the merged CRM DEMs. For CRM grid cells within features from DEM_artifacts.shp that indicated a merging error in an offshore area where the dataset had an elevation of less than or equal to 0 meters (type = "Merging", Loc="offshore" or "both"), the SciPy 0.17.0 function griddata was used in Python 2.7.11 to bilinearly interpolate over the erroneous values (method="linear"). Grid cells with centers inside a stitching error feature had their values set to NaN (not a number), and the grid cell locations were then used as "unknown" value locations to receive the interpolated values. PyShp 1.2.1, Shapely 1.5.12, GDAL 1.11.1 were used in Python 2.7.11 to select the grid cells corresponding to the stitching artifacts. For the interpolation step, stitching errors above 0 meters elevation in the CRM data were not changed unless the stitching feature contained the additional flag of "higher" (DEM_artifacts.shp, Action="higher"), which set the maximum interpolation elevation to 5 meters instead of 0 meters. This "higher" option was only used for the seam between the northwest Pacific region and the Vancouver bathymetry data. Data sources used in this process:
    • east_CRM_NAD.tif
    Data sources produced in this process:
    • east_CRM.tif
    Date: 2016 (process 11 of 17)
    Step 11. Merge elevation products: Merging the CRM and NED data required multiple steps to extract the highest quality data from each source while ensuring a smooth boundary across the continuum between bathymetric and topographic elevations, chosen for visual purposes as -10 to 10 meters. The individual steps for the merge are expanded as substeps. Two differences between the CRM and NED datasets led to the development of this multiple step merging procedure. First, NED data are always based on a vertical datum of NAVD 88, but NED data are nominally assigned a value of 0.0 meters elevation for anywhere with an elevation less than or equal to 0 meters. However, many anomalous, non-zero values persist for marine or other coastal waters due to the source datasets as well as other processing used in NED creation. Thus, only using a cutoff of 0 meters elevation to snap CRM bathymetry data into NED will result in anomolous "islands". Additionally, in some coastal waterbodies, NED may have positive elevations, whereas CRM contains bathymetry with elevations below sea level. Secondly, CRM data above 0 meters elevation are only whole numbers with no non-zero decimals and also appear smoothed, potentially due to a processing step in CRM creation. This rounding in CRM smears the interface between bathymetric and topographic data (i.e., 0 to 1 meters) and creates the problem that coastal areas with elevations below 0.5 meters may have been assigned to 0 meters. Thus, no single value in neither NED nor CRM allowed the extraction and insertion of one dataset into the other. Instead, CRM values equal to and above 0 meters elevation were assigned values from NED. Then, NED elevations less than 8 meters above sea level (0 meters, NAVD88) were replaced with the edited CRM values. This assigned bathymetric data in coastal areas where it was available in CRM without relying on only one of the datasets to specify the coastal boundary (e.g., a coastal pond with a water elevation of 3 meters in NED can be supplied with CRM bathymetry data so long as CRM elevation is less than 0 meters). Data sources used in this process:
    • east_NED.tif
    • east_CRM.tif
    Data sources produced in this process:
    • east_cdem.tif
    Date: 2016 (process 12 of 17)
    Step 11a. Fill NED data with CRM: CRM values were assigned where the NED data were null (i.e., in areas far offshore) using ArcGIS 10.3 and the Raster Calculator command "east_NED_filled.tif = Con(IsNull(east_NED.tif),east_CRM.tif,east_NED.tif)" with the output extent set to the union of inputs in Environment Settings. Data sources used in this process:
    • east_NED.tif
    • east_CRM.tif
    Data sources produced in this process:
    • east_NED_filled.tif
    Date: 2016 (process 13 of 17)
    Step 11b. Set CRM topography to null: CRM values were set to null values if they equaled or were above 0 meters of elevation using ArcGIS 10.3 and the Raster Calculator command "east_CRM_null.tif = SetNull(east_CRM.tif greater than 0 ,east_CRM.tif)" with default Environment Settings. Data sources used in this process:
    • east_CRM.tif
    Data sources produced in this process:
    • east_CRM_null.tif
    Date: 2016 (process 14 of 17)
    Step 11c. Fill CRM_null data with NED_filled: The filled NED elevations were used to assign elevation values to the nulled CRM resulting in a temporary raster with original CRM bathymetry below 0 meters elevation and NED elevations otherwise. This step used ArcGIS 10.3 and the Raster Calculator command "east_CRM_null_filled.tif = Con(IsNull(east_CRM_null.tif),east_NED_filled.tif,east_CRM_null.tif)" with the output extent set to the union of inputs in Environment Settings. Data sources used in this process:
    • east_NED_filled.tif
    • east_CRM_null.tif
    Data sources produced in this process:
    • east_CRM_null_filled.tif
    Date: 2016 (process 15 of 17)
    Step 11d. Merge adjusted CRM and NED datasets: The adjusted CRM and NED datasets were merged by extracting low elevation areas from the NED-filled CRM raster and higher elevations from the CRM-filled NED raster using ArcGIS 10.3 and the Raster Calculator command "east_cdem.tif = Con(east_NED_filled.tif less than 8,east_CRM_null_filled.tif,east_NED_filled.tif)" with default Environment Settings. Data sources used in this process:
    • east_NED_filled.tif
    • east_CRM_null_filled.tif
    Data sources produced in this process:
    • east_cdem.tif
    Date: 2016 (process 16 of 17)
    Step 12. Extract coastal elevations: A polygonal mask was manually drawn around the extent of the planned coastal groundwater models ("dem_mask.shp"). The mask was extended offshore a considerable distance to allow the dataset to be used for other purposes. No consistent offshore extent was used (i.e., did not use a bathymetric contour or a buffer from shore). Instead, the mask was drawn a relatively consistent distance offshore that still contained bathymetric data. The terrestrial extent was chosen solely based on the potential groundwater model extents. The extraction was achieved by using ArcGIS 10.3 Spatial Analyst\Extraction\Extract by mask tool with default settings using dem_mask.shp as the mask. No data values in west_cdem_v1.tif and east_cdem_v1.tif represent both where the mask did not extract elevations and where the underlying datasets contained no data values or were not downloaded for a particular area. Both NED and CRM data outside of the mask can be joined to west_cdem_v1.tif and east_cdem_v1.tif using either the Raster Calculator conditional merging procedure in Step 5 or using the Mosaic tools in ArcGIS or software and environments capable of handling GeoTiff data. Data sources used in this process:
    • east_cdem.tif
    Data sources produced in this process:
    • dem_mask.shp
    • east_cdem_v1.tif
    Date: 07-Aug-2020 (process 17 of 17)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    Digital elevation data from multiple sources were compared and those of highest quality and consistency for a given region were used.
  2. How accurate are the geographic locations?
    The horizontal accuracy of the terrain model inherits the horizontal accuracy from the source datasets. The horizontal accuracy is superceded in the final terrain models by the aggregation procedure that reduces the resolution of the original datasets to the final resolution.
  3. How accurate are the heights or depths?
    The vertical accuracy of the terrain model inherits the vertical accuracy from the source datasets. The vertical accuracy is superceded in the final terrain models by the aggregation procedure that reduces the resolution of the original datasets to the final resolution. Where possible, datasets with a vertical datum of the North American Vertical Datum of 1988 (NAVD88) were used. However, many datasets contain either no datum information or do not consolidate to a single datum. This conflict in vertical datums is one reason why the data release contains a horizontal resolution of 1-arcsecond (or about 100 meters): the real variability and range of elevation across the area of one raster cell is often larger than the offset of a particular datum choice (roughly 0 to 2 meters). Thus, while the resolution of the data is high in the terrestrial setting (reported by U.S. Geological Survey National Elevation Dataset as 0.01 meters), the bathmetric vertical accuracy is spatially variable and relative to the tidal range in a particular area. Thus, the vertical accuraccy of the final product is ~0.01 to ~2 meters.
  4. Where are the gaps in the data? What is missing?
    Data set is considered complete for the information presented. The coastal margins of the contiguous United States are included in this data release as two separate 32-bit GeoTiff rasters. Elevation data inland of the current data release can be supplemented with the U.S. Geological Survey National Elevation Dataset or other terrestrial elevation products. Bathymetric beyond the extents of this data release can be supplemented with the NOAA Coastal Relief Model or other bathymetric products. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    The individual and merged datasets were checked for accuracy in the coastal area using coloring schemes that highlighted elevations near sea level (e.g., -10 meters to 10 meters). Beyond this elevation range, the accuracy of the merged product is inherited from the underlying datasets.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: none
Use_Constraints:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset. These data are not for navigational use.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    USA

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? east_cdem_v1.zip: ZIP file contains the 32-bit GeoTiff and associated world file (.tfw), a browse thumbnail, and the associated FGDC metadata.
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the U.S. Geological Survey, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 16-Nov-2021
Metadata author:
Kevin M. Befus
University of Wyoming
University of Wyoming
Laramie, WY
USA

307-766-2390 (voice)
whsc_data_contact@usgs.gov
Contact_Instructions:
Kevin is currently with the University of Wyoming as an Assistant Professor in the Civil and Architectural Engineering Department. His contact information has been updated to reflect this. The metadata contact email address is a generic address in the event the metadata contact is no longer with the USGS or the email is otherwise invalid.
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_F7W37TGK/east_cdem_v1.tif.faq.html>
Generated by mp version 2.9.50 on Tue Nov 16 10:06:28 2021