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

Metadata also available as - [Outline] - [Parseable text] - [XML]

Frequently anticipated questions:


What does this data set describe?

Title:
Continuous and optimized 3-arcsecond elevation model for the United States west 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 assimilation 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., 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 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 west 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., 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: -125.306216
    East_Bounding_Coordinate: -115.998716
    North_Bounding_Coordinate: 49.312078
    South_Bounding_Coordinate: 30.999578
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/57ebe8dbe4b09082500ef4ad?name=west_cDEM_overview.png (PNG)
    Color image of terrain model for contiguous U.S. west 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. west coast 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:-3790.8
    Maximum:4392.0
    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. 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 assimilation 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.

How was the data set created?

  1. From what previous works were the data drawn?
    southern_calif_crm_v2_netcdf.zip (source 1 of 5)
    NOAA National Centers for Environmental Information, unknown, US Coastal Relief Model - Southern California Version 2: 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 1-arcsecond. Note that the data files for this reference were a zipped directory containing .grd format rasters, but the linkage incorrectly indicated the data were in NetCDF format on the retrieval date. 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 .grd files in the .zip were merged into a topography and bathymetry product. Elevations less than or equal to 0 meters were used to create the final elevation model.
    central_pacific_crm_v1.flt (source 2 of 5)
    NOAA National Centers for Environmental Information, unknown, US Coastal Relief Model - Central Pacific: 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_pacific_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_pacific_crm_v1 data were not directly used for areas with merging or channel type artifacts nor where other elevation data were used to replace central_pacific_crm_v1 data, outlined in DEM_artifacts.shp.
    nw_pacific_crm_v1.flt (source 3 of 5)
    NOAA National Centers for Environmental Information, unknown, US Coastal Relief Model - Northwest Pacific: 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 nw_pacific_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. nw_pacific_crm_v1 data were not directly used for areas with merging or channel type artifacts nor where other elevation data were used to replace nw_pacific_crm_v1 data, outlined in DEM_artifacts.shp.
    individual NED tiles (source 4 of 5)
    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.
    092G.bag (source 5 of 5)
    Service, Canadian Hydrographic, 2014, 500m Bathymetry: Fisheries and Oceans Canada, Canadian Hydrographic Service.

    Online Links:

    Other_Citation_Details:
    The horizontal datum for the dataset is global Mercator (Mercator_1SP,EPSG 9804). The vertical datum is "Unknown". The cell size is 500 meters. Additional information can be found in the dataset metadata (http://geoportal.gc.ca/data/500m_Bathymetry/092G_Metadata.xml). DISCLAIMER: "This product has been produced by or for the U.S. Geological Survey and includes data provided by the Canadian Hydrographic Service of the Department of Fisheries and Oceans. The incorporation of data sourced from the Canadian Hydrographic Service of the Department of Fisheries and Oceans within this product does NOT constitute an endorsement by the Canadian Hydrographic Service or the Department of Fisheries and Oceans of this product."
    Type_of_Source_Media: Raster
    Source_Contribution:
    This dataset was used to supply values where the merged CRM and NED datasets were missing bathymetry values.
  2. How were the data generated, processed, and modified?
    Date: 2016 (process 1 of 14)
    Step 1. Download CRM regions: Coastal Relief Model (CRM) data were downloaded in binary float format except for southern California, which was downloaded as a zip folder of .grd files. The southern California individual .grd files were merged in alphabetical order 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" and all other options as defaults. 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.
    Data sources used in this process:
    • southern_calif_crm_v2_netcdf.zip
    Data sources produced in this process:
    • socal_pacific_crm_v2.tif
    Date: 2016 (process 2 of 14)
    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:
    • west_NED.tif
    Date: 2016 (process 3 of 14)
    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 14)
    Step 4. Supplementary data download: Additional 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 the Canadian Hydrographic Service. The source name of this step corresponds to the source identifier name and is the original downloaded dataset. Data sources used in this process:
    • 092G.bag
    Date: 2016 (process 5 of 14)
    Step 5. Central and Northwestern Pacific region corrections: In the central_pacific_crm_v1.flt and nw_pacific_crm_v1.flt, coastal inlets and low elevation river channels with elevation artifacts were filled. First, the artifacts were identified as type = "channel" artifacts in DEM_artifacts.shp, although these artifacts were primarily associated with merging CRM 1 degree cells, and given a flag attribute to "fill" (Action="fill"). Then, the original CRM .flt's were individually filled using the ArcGIS 10.3 Spatial Analyst\Hydrology\Fill tool with default settings, yielding temporary rasters "nwp_filled" and "cp_filled". The features with the channel artifacts were then used to extract the filled elevation data by mask and were merged with the original CRM DEMs using the Extract by mask and Raster calculator merging procedure in Step 5 with the output extents set to the CRM .flt files. Data sources used in this process:
    • central_pacific_crm_v1.flt
    • nw_pacific_crm_v1.flt
    Data sources produced in this process:
    • central_pacific_crm_vc.tif
    • nw_pacific_crm_vc.tif
    Date: 2016 (process 6 of 14)
    Step 6. Add Vancouver bathymetry: To extend the bathymetric data smoothly into Canada on the west coast, an additional bathymetric dataset was required. The Vancouver data, 092G.bag, was converted to GeoTiff using Hydroffice.bag 0.2.15 BAGFile command to load the data and elevation.Elevation2Gdal to export the GeoTiff file ("CHS_Vancouver_500m_proj.tif"). The cooridinate system for CHS_Vancouver_500m_proj.tif was assigned with the ArcGIS 10.3 Data Management\Projections and Transformations\Define Projection tool with the Coordinate System specified as World_Mercator. CHS_Vancouver_500m_proj.tif was projected to the WGS_1984 geographic coordinate system as a temporary raster ("CHS_Vancouver_500m.tif") using ArcGIS 10.3 Data Management\Projections and Transformations\Raster\Project Raster tool using an output cell size of 3-arcseconds, BILINEAR interpolation for the resampling technique, and otherwise default values. CHS_Vancouver_500m.tif was first set to null above 0 meters elevation and then merged with nw_pacific_crm_vc.tif. CHS_Vancouver_500m.tif values were used directly for cells where nw_pacific_crm_vc.tif was null. The merge used the ArcGIS 10.3 Raster Calculator command "nw_pacific_crm_vc2.tif = Con(IsNull(SetNull(CHS_Vancouver_500m.tif greater than 0,CHS_Vancouver_500m.tif)),Con(IsNull(nw_pacific_crm_vc.tif),CHS_Vancouver_500m.tif,nw_pacific_crm_vc.tif),CHS_Vancouver_500m.tif)" with the cell size set to 1-arcsecond, the output coordinate system to the same as nw_pacific_crm_vc.tif, and the output extent to the union of inputs in the environmental settings. Raster Calculator automatically resampled CHS_Vancouver_500m.tif to match the output cell size. Low data density at the southern end of Vancouver Island in the nw_pacific_crm_vc2.tif led to unavoidable artifacts that persist to the final raster product, west_cdem_v1.tif. Data sources used in this process:
    • 092G.bag
    • nw_pacific_crm_vc.tif
    Data sources produced in this process:
    • nw_pacific_crm_vc2.tif
    Date: 2016 (process 7 of 14)
    Step 7. 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:
    • central_pacific_crm_vc.tif
    • nw_pacific_crm_vc2.tif
    • socal_pacific_crm_v2.tif
    Data sources produced in this process:
    • west_CRM_NAD.tif
    Date: 2016 (process 8 of 14)
    Step 8. 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:
    • west_CRM_NAD.tif
    Data sources produced in this process:
    • west_CRM.tif
    Date: 2016 (process 9 of 14)
    Step 9. 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:
    • west_NED.tif
    • west_CRM.tif
    Data sources produced in this process:
    • west_cdem.tif
    Date: 2016 (process 10 of 14)
    Step 9a. 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 "west_NED_filled.tif = Con(IsNull(west_NED.tif),west_CRM.tif,west_NED.tif)" with the output extent set to the union of inputs in Environment Settings. Data sources used in this process:
    • west_NED.tif
    • west_CRM.tif
    Data sources produced in this process:
    • west_NED_filled.tif
    Date: 2016 (process 11 of 14)
    Step 9b. 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 "west_CRM_null.tif = SetNull(west_CRM.tif > 0 ,west_CRM.tif)" with default Environment Settings. Data sources used in this process:
    • west_CRM.tif
    Data sources produced in this process:
    • west_CRM_null.tif
    Date: 2016 (process 12 of 14)
    Step 9c. 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 "west_CRM_null_filled.tif = Con(IsNull(west_CRM_null.tif),west_NED_filled.tif,west_CRM_null.tif)" with the output extent set to the union of inputs in Environment Settings. Data sources used in this process:
    • west_NED_filled.tif
    • west_CRM_null.tif
    Data sources produced in this process:
    • west_CRM_null_filled.tif
    Date: 2016 (process 13 of 14)
    Step 9d. 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 "west_cdem.tif = Con(west_NED_filled.tif < 8,west_CRM_null_filled.tif,west_NED_filled.tif)" with default Environment Settings. Data sources used in this process:
    • west_NED_filled.tif
    • west_CRM_null_filled.tif
    Data sources produced in this process:
    • west_cdem.tif
    Date: 2016 (process 14 of 14)
    Step 10. 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:
    • west_cdem.tif
    Data sources produced in this process:
    • dem_mask.shp
    • west_cdem_v1.tif
  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? west_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: 30-Jan-2017
Metadata author:
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.
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/eastcoast/bathymetry/west_cdem_v1.tif.faq.html>
Generated by mp version 2.9.49 on Mon Sep 10 17:45:02 2018