Topobathymetric digital elevation model of Elim, Alaska, 2019 to 2021

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Frequently anticipated questions:

What does this data set describe?

Title:
Topobathymetric digital elevation model of Elim, Alaska, 2019 to 2021
Abstract:
This dataset contains a 1-meter resolution, seamless topobathymetric digital elevation model (TBDEM) and associated spatial metadata for Elim, Alaska. The TBDEM contains best available multi-source topographic and bathymetric elevation data collected between the years 2019 and 2021. Processing was done by the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC) and results are provided as a Cloud Optimized GeoTIFF (COG).
Supplemental_Information:
Work was funded by Title VII of Division N in the Consolidated Appropriations Act, 2023 (Public Law 117–328) to support direct recovery and rebuilding decisions in the wake of declared disasters related to hurricanes and typhoons in 2022. For more information on these efforts, see https://www.usgs.gov/supplemental-appropriations-for-disaster-recovery-activities/typhoon-merbok-coastal-community. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the dataset in nonproprietary form, this metadata file may include some vendor-specific terminology.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document the dataset in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology.
  1. How might this data set be cited?
    Nereson, Alexander L., Gibbs, Ann E., and Erikson, Li H., 20250708, Topobathymetric digital elevation model of Elim, Alaska, 2019 to 2021: data release DOI: 10.5066/P13BXTXV, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Nereson, Alexander L., Gibbs, Ann E., and Erikson, Li H., 2025, Topobathymetric digital elevation models – coastal Alaska: U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    Other_Citation_Details:
    Suggestion citation: Nereson, A.L., Gibbs, A.E., and Erikson, L.H., 2025, Topobathymetric digital elevation models – coastal Alaska: U.S. Geological Survey data release, https://doi.org/10.5066/P13BXTXV.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -162.29760
    East_Bounding_Coordinate: -162.22087
    North_Bounding_Coordinate: 64.62899
    South_Bounding_Coordinate: 64.59660
  3. What does it look like?
    elim_2019_2021_browse.png (PNG)
    Quick view image of seamless topobathymetric digital elevation model for Elim, Alaska
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2019
    Ending_Date: 2021
    Currentness_Reference:
    ground condition at the time source data were collected
  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?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 3106 x 3138 x 1, type Grid Cell
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 3
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -165.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 1.0
      Ordinates (y-coordinates) are specified to the nearest 1.0
      Planar coordinates are specified in meters
      The horizontal datum used is NAD83_National_Spatial_Reference_System_2011.
      The ellipsoid used is GRS 1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101004.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    elim_tbdem_1m_2019_to_2021.tif
    Raster geospatial data file. (Source: Producer Defined)
    Elevation
    Orthometric height in meters NAVD88 (GEOID12B). Values of -9999 = no data. (Source: Producer Defined)
    ValueDefinition
    -9999No Data
    Range of values
    Minimum:-6.641
    Maximum:185.701
    Units:meters
    Resolution:0.001
    Entity_and_Attribute_Overview:
    These metadata describe a Cloud Optimized GeoTIFF (COG) raster file whose floating point grid cell values represent orthometric heights (elevations) in meters NAVD88 GEOID12B. The file name for the elevation raster follows the format: “location_tbdem_1m_YYYY_to_YYYY.tif”, where “location” is the geographic name of the place depicted in the data, “tbdem” indicates “topobathymetric digital elevation model”, “1m” indicates 1-meter grid resolution, and “YYYY_to_YYYY” indicates the date range (in years) of all the source data. The source data are further described in a supplementary "spatial" metadata file that contains polygonal boundaries and descriptive attributes for each source. Polygons and attributes are saved as a feature class in an Esri file geodatabase with a file name that follows the naming convention described above, along with the following suffix: "_spatial_metadata.gdb". The file geodatabase has been compressed into a ZIP file of the same name. The following attribute fields are included in the polygon feature class: Name of dataset (Title), the organization major project or activity (Source_Project), source dataset organization (Source_Organization), date(s) acquired (Date_Acquired), publication date (Publication Date), source elevation type (Data_Type), source projection (Source_Projection), source horizontal resolution (Source_Horizontal_Resolution), source horizontal datum (Source_Horizontal_Datum), source vertical units (Source_Vertical_Units), source vertical datum (Source_Vertical_Datum), source geoid (Geoid), spatial extent of source (Coverage_Area), source URL (Source_Publication), perimeter of polygon feature in meters (Shape_Length), and area of polygon feature in square meters (Shape_Area). Descriptive attributes for interpolation guides are set to Null. See Process Steps above for more information on how and where guides were created.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Alexander L. Nereson
    • Ann E. Gibbs
    • Li H. Erikson
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    PCMSC Science Data Coordinator
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

This product was created to help advance coastal storm response and recovery in Alaskan coastal communities in the wake of the September 2022 extratropical Typhoon Merbok disaster. It is being used by the USGS to support the development of dynamic flood models for more than 20 communities along the northwest coasts of Alaska. This product is intended for reuse by scientists, managers, and the general public. These data can be opened with most geographic information systems (GIS) software for data visualization and analysis purposes.

How was the data set created?

  1. From what previous works were the data drawn?
    2021 USACE tblidar (source 1 of 6)
    U.S. Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of eXpertise (JALBTCX), 2024, 2021 USACE NCMP Topobathy Lidar DEM: Alaska: NOAA Office for Coastal Management, online.

    Online Links:

    Type_of_Source_Media: Digital and/or Hardcopy
    Source_Contribution:
    Elevations in this data source were used with the other source data to interpolate a seamless topobathymetric digital elevation model.
    2019 USACE multibeam (source 2 of 6)
    District, USACE Alaska, 2020, Elim Bathymetry: USACE Alaska District, available on request.

    Online Links:

    Type_of_Source_Media: Digital and/or Hardcopy
    Source_Contribution:
    Elevations in this data source were used with the other source data to interpolate a seamless topobathymetric digital elevation model.
    conversion constant (source 3 of 6)
    National Oceanic and Atmospheric Administration (NOAA), 2025, NOAA Tides and Currents: National Oceanic and Atmospheric Administration (NOAA), online.

    Online Links:

    Type_of_Source_Media: online database
    Source_Contribution: Local conversion constants
    conversion constant (source 4 of 6)
    Alaska Department of Natural Resources, 2025, Alaska Tidal Datum Portal: Alaska Department of Natural Resources, online.

    Online Links:

    Type_of_Source_Media: online database
    Source_Contribution: Local conversion constants
    Community Profile CAD (source 5 of 6)
    Alaska Department of Commerce, Community, & Economic Development (AK DCRA), 2025, Community Profile CAD Planimetric Features: Alaska Department of Commerce, Community, & Economic Development, online.

    Online Links:

    Type_of_Source_Media: online database
    Source_Contribution: Community profile feature layer used to identify culverts
    ShoreZone (source 6 of 6)
    National Oceanic and Atmospheric Administration (NOAA), 2025, Alaska ShoreZone Mapping Website: National Oceanic and Atmospheric Administration (NOAA), online.

    Online Links:

    Type_of_Source_Media: online database
    Source_Contribution: oblique aerial imagery used to identify culverts
  2. How were the data generated, processed, and modified?
    Date: 30-Apr-2025 (process 1 of 10)
    Define an area of interest (AOI) and gather published topographic and bathymetric elevation datasets with coverage in the AOI.
    Date: 30-Apr-2025 (process 2 of 10)
    View and prioritize source elevation datasets based on date of acquisition, spatial distribution, accuracy, and point density. In general, more recent dates of acquisition, wider spatial distribution, higher accuracy, and higher point density result in a higher priority level. Source elevation datasets are listed in their order of priority in the Lineage section of this metadata file and in the associated spatial metadata, where the first source dataset is of the highest priority. Data sources used in this process:
    • 2021 USACE tblidar
    • 2019 USACE multibeam
    Date: 30-Apr-2025 (process 3 of 10)
    Prepare each source elevation dataset, as applicable. In Global Mapper software: A) transform the source dataset from its native horizontal and vertical spatial reference systems to the appropriate NAD83 (2011) Universal Transverse Mercator (UTM) zone projection and to NAVD88 GEOID12B, respectively. Convert source elevations to NAVD88 by adding a local conversion constant to the native tidal/ellipsoidal heights of the source dataset. Conversion constants used for this work come from NOAA Tides and Currents (https://tidesandcurrents.noaa.gov/) or the Alaska Tidal Datum Portal (https://dggs.alaska.gov/hazards/coastal/ak-tidal-datum-portal.html) for the most recent available tidal epoch for the tide station nearest to the AOI. The local constants used for this project are listed in the last process step of this metadata file, along with any additional transformations that may have been used bring source datasets into NAVD88 GEOID12B. B) Save the transformed dataset as a LAZ point file. C) Clip LAZ point file to AOI polygon. D) Classify and remove non-ground points from structure-from-motion (SfM)-derived digital surface models (DSMs) using lidar auto-classification. E) Spatially thin LAZ file to one-meter resolution, using the minimum value method. F) Clip the LAZ file to all higher-priority datasets using a buffer of 2x the average point density/resolution of the source dataset being prepared. G) Split the LAZ file into two subsets, one containing 95 percent of the points (active points) and the other containing the remaining 5 percent, or every 20th point (check points). The active points are later gridded in the elevation model along with associated interpolation guides to derive the final topographic surface, while the check points are used to compute the interpolation accuracy of the derived surface. Data sources used in this process:
    • conversion constant
    Date: 30-Apr-2025 (process 4 of 10)
    Create interpolation guides. Interpolation guides are author-defined 3D points, lines, or polygons used to help derive the final topographic surface. Interpolation guides are used to A) smooth or accentuate breaks in slope along shared boundaries of source datasets, B) prevent topographic creep/shoreline migration from onshore regions into offshore regions, C) fill data gaps in source datasets with plausible heights when local knowledge, qualitative field observations, remotely sensed optical imagery, or other information sources are available, or D) otherwise facilitate the seamless integration of all source datasets. Details of interpolation guides used to create the final elevation surface for this release are listed in the last process step of this metadata file.
    Date: 30-Apr-2025 (process 5 of 10)
    Interpolate a one-meter resolution seamless elevation surface from input source data and interpolation guides using the Create Elevation Grid tool (triangulation method).
    Date: 30-Apr-2025 (process 6 of 10)
    Export grid as a Cloud Optimized GeoTIFF (COG) using Global Mapper, clipping the grid bounds to the project AOI and snapping the output raster cells to the appropriate UTM zone projection, using a bilinear resampling method.
    Date: 30-Apr-2025 (process 7 of 10)
    Quantify interpolation error in MATLAB by calculating the mean bias error (MBE) and root mean square error (RMSE) of the final, seamless TBDEM relative to the check point subsets. MBE and RMSE are reported in the Vertical Positional Accuracy section of this metadata file.
    Date: 30-Apr-2025 (process 8 of 10)
    Create spatial metadata for each source dataset by converting LAZ points to simplified bounding polygons and save in an Esri file geodatabase feature class, along with descriptive attributes about the source dataset. Spatial metadata files are further described in the Entity and Attribute Overview section of this metadata file.
    Date: 30-Apr-2025 (process 9 of 10)
    Perform quality checks on the output elevation raster and spatial metadata files, including review of minimum/maximum elevation values, shoreline positions, gridding artifacts, and descriptive attributes.
    Date: 30-Apr-2025 (process 10 of 10)
    Special considerations: A) Vertical datum conversion constants: 0 m NAVD88 is -0.782 meters above Mean Lower Low Water (MLLW) (at NOAA CO-OPS tide station: 9468863 ELIM, NORTON BAY, AK, via Alaska Tidal Datum Portal). B) Additional vertical transformations: none. C) Culverts were identified using the AK DCRA Community Profile CAD Planimetric Features layer (https://dcra-cdo-dcced.opendata.arcgis.com/maps/7f5ca7eafcbb40dc88c06a8a5072b6e3/about) and NOAA ShoreZone oblique aerial imagery (https://alaskafisheries.noaa.gov/mapping/sz/). Each culvert was digitized into a 3D polygon and used in the interpolation step above. Bathymetric contour guides (author-defined points) were created to fill bathymetric data gaps and to prevent topographic creep in shallow areas. Data sources used in this process:
    • conversion constant
    • Community Profile CAD
    • ShoreZone
  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?
    No formal attribute accuracy tests were conducted.
  2. How accurate are the geographic locations?
    The horizontal accuracy of the final seamless TBDEM was not assessed quantitatively. Please refer directly to the elevation data sources for measures of accuracy and uncertainty, when available.
  3. How accurate are the heights or depths?
    The authors calculated the mean bias error (MBE) and root mean square error (RMSE) of the final, seamless TBDEM relative to the check point subsets for Elim, Alaska. The MBE (TBDEM minus all check points) is -0.031 m and the RMSE is 0.124 m. For other measures of vertical accuracy, please refer directly to the metadata for each input data source cited below.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. 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?
    No formal logical accuracy tests were conducted.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints
Use_Constraints USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data. This information is not intended for navigation purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - CMGDS
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov
  2. What's the catalog number I need to order this data set? These data are available in Cloud Optimized GeoTIFF (COG) raster file format accompanied by a spatial metadata geodatabase file and CSDGM FGDC-compliant metadata.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: Cloud Optimized GeoTIFF (COG) raster file whose floating point grid cell values represent orthometric heights (elevations). No data value is -9999. in format GeoTIFF (version Global Mapper v25.0 and ArcGIS Pro 3.4) Size: 21.2
      Network links: https://doi.org/10.5066/P13BXTXV
    • Cost to order the data: None

  5. What hardware or software do I need in order to use the data set?
    Most geospatial data software and their supporting operating systems (for example, QGIS, Global Mapper, Esri ArcGIS Pro, or similar).

Who wrote the metadata?

Dates:
Last modified: 08-Jul-2025
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/CMGDS_DR_tool/DR_P13BXTXV/elim_tbdem_1m_2019_to_2021_metadata.faq.html>
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