Quality checks were performed on the elevation raster and spatial metadata files, including review of minimum/maximum elevation values, shoreline positions, gridding artifacts, and descriptive attributes. Data values fall within expected ranges.
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.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
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.
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
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 Nome, Alaska. The MBE (TBDEM minus all check points) is 0.001 m and the RMSE is 0.055 m. For other measures of vertical accuracy, please refer directly to the metadata for each input data source cited below.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
Office of Coast Survey, National Ocean Service, NOAA, U.S. Department of Commerce
Publication_Date: 2024
Title: H13695: NOS Hydrographic Survey, Norton Sound, AK, Nome Harbor
Geospatial_Data_Presentation_Form: raster digital data
Publication_Information:
Publication_Place: online
Publisher: NOAA National Centers for Environmental Information
Online_Linkage: https://www.ngdc.noaa.gov/nos/H12001-H14000/H13695.html
Type_of_Source_Media: Digital and/or Hardcopy
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2023
Source_Currentness_Reference: ground condition at time data were collected
Source_Citation_Abbreviation: 2023 NOS harbor multibeam
Source_Contribution:
Elevations in this data source were used with the other source data to interpolate a seamless topobathymetric digital elevation model.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
U.S. Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of eXpertise (JALBTCX)
Publication_Date: 2024
Title: 2021 USACE NCMP Topobathy Lidar DEM: Alaska
Geospatial_Data_Presentation_Form: raster digital data
Publication_Information:
Publication_Place: online
Publisher: NOAA Office for Coastal Management
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/73829/
Type_of_Source_Media: Digital and/or Hardcopy
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2021
Source_Currentness_Reference: ground condition at time data were collected
Source_Citation_Abbreviation: 2021 NCMP tblidar
Source_Contribution:
Elevations in this data source were used with the other source data to interpolate a seamless topobathymetric digital elevation model.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
U.S. Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of eXpertise (JALBTCX)
Publication_Date: 2020
Title: 2019 USACE NCMP Topobathy Lidar DEM: Alaska
Geospatial_Data_Presentation_Form: raster digital data
Publication_Information:
Publication_Place: online
Publisher: NOAA Office for Coastal Management
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/59419
Type_of_Source_Media: Digital and/or Hardcopy
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2019
Source_Currentness_Reference: ground condition at time data were collected
Source_Citation_Abbreviation: 2019 NCMP tblidar
Source_Contribution:
Elevations in this data source were used with the other source data to interpolate a seamless topobathymetric digital elevation model.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
Office of Coast Survey, National Ocean Service, NOAA, U.S. Department of Commerce
Publication_Date: 2024
Title:
H13696: NOS Hydrographic Survey, Norton Sound, AK, Approaches to Nome Harbor
Geospatial_Data_Presentation_Form: raster digital data
Publication_Information:
Publication_Place: online
Publisher: NOAA National Centers for Environmental Information
Online_Linkage: https://www.ngdc.noaa.gov/nos/H12001-H14000/H13696.html
Type_of_Source_Media: Digital and/or Hardcopy
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2023
Source_Currentness_Reference: ground condition at time data were collected
Source_Citation_Abbreviation: 2023 NOS harbor approach multibeam
Source_Contribution:
Elevations in this data source were used with the other source data to interpolate a seamless topobathymetric digital elevation model.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
Alaska Department of Natural Resources, Division of Geological and Geophysical Surveys
Publication_Date: 2016
Title:
Photogrammetric digital surface models and orthoimagery for 26 coastal communities of western Alaska: Nome DSM
Geospatial_Data_Presentation_Form: raster digital data
Publication_Information:
Publication_Place: online
Publisher:
Alaska Department of Natural Resources, Division of Geological and Geophysical Surveys
Online_Linkage: https://dggs.alaska.gov/pubs/id/29548
Type_of_Source_Media: Digital and/or Hardcopy
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2015
Source_Currentness_Reference: ground condition at time data were collected
Source_Citation_Abbreviation: 2015 DGGS sfm
Source_Contribution:
Elevations in this data source were used with the other source data to interpolate a seamless topobathymetric digital elevation model.
Source_Information:
Source_Citation:
Citation_Information:
Originator: Claire Porter
Originator: Ian Howat
Originator: Myoung-Jon Noh
Originator: Erik Husby
Originator: Samuel Khuvis
Originator: Evan Danish
Originator: Karen Tomko
Originator: Judith Gardiner
Originator: Adelaide Negrete
Originator: Bidhyananda Yadav
Originator: James Klassen
Originator: Cole Kelleher
Originator: Michael Cloutier
Originator: Jesse Bakker
Originator: Jeremy Enos
Originator: Galen Arnold
Originator: Greg Bauer
Originator: Paul Morin
Publication_Date: 2023
Title: ArcticDEM, Version 4.1
Geospatial_Data_Presentation_Form: raster digital data
Publication_Information:
Publication_Place: online
Publisher: Polar Geospatial Center, University of Minnesota
Online_Linkage:
Online_Linkage: https://www.pgc.umn.edu/data/arcticdem/
Type_of_Source_Media: Digital and/or Hardcopy
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 2008
Ending_Date: 2021
Source_Currentness_Reference: ground condition at time data were collected
Source_Citation_Abbreviation: PGC ArcticDEM v 4.1
Source_Contribution:
Elevations in this data source were used with the other source data to interpolate a seamless topobathymetric digital elevation model.
Source_Information:
Source_Citation:
Citation_Information:
Originator: National Oceanic and Atmospheric Administration (NOAA)
Publication_Date: 2023
Title: NOAA Tides and Currents
Publication_Information:
Publication_Place: online
Publisher: National Oceanic and Atmospheric Administration (NOAA)
Online_Linkage: https://tidesandcurrents.noaa.gov/
Type_of_Source_Media: online database
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2023
Source_Currentness_Reference: date data were accessed
Source_Citation_Abbreviation: conversion constant
Source_Contribution: Local conversion constants
Source_Information:
Source_Citation:
Citation_Information:
Originator: Alaska Department of Natural Resources
Publication_Date: 2023
Title: Alaska Tidal Datum Portal
Publication_Information:
Publication_Place: online
Publisher: Alaska Department of Natural Resources
Online_Linkage:
Type_of_Source_Media: online database
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2023
Source_Currentness_Reference: date data were accessed
Source_Citation_Abbreviation: conversion constant
Source_Contribution: Local conversion constants
Source_Information:
Source_Citation:
Citation_Information:
Originator: National Oceanic and Atmospheric Administration (NOAA)
Publication_Date: 2023
Title: Alaska ShoreZone Mapping Website
Publication_Information:
Publication_Place: online
Publisher: National Oceanic and Atmospheric Administration (NOAA)
Online_Linkage: https://alaskafisheries.noaa.gov/mapping/sz/
Type_of_Source_Media: online database
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2023
Source_Currentness_Reference: date data were accessed
Source_Citation_Abbreviation: ShoreZone
Source_Contribution: oblique aerial imagery used to identify culverts
Process_Step:
Process_Description:
Define an area of interest (AOI) and gather published topographic and bathymetric elevation datasets with coverage in the AOI.
Process_Date: 20250902
Process_Step:
Process_Description:
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.
Source_Used_Citation_Abbreviation: 2023 NOS harbor multibeam
Source_Used_Citation_Abbreviation: 2021 NCMP tblidar
Source_Used_Citation_Abbreviation: 2019 NCMP tblidar
Source_Used_Citation_Abbreviation: 2023 NOS harbor approach multibeam
Source_Used_Citation_Abbreviation: 2015 DGGS sfm
Source_Used_Citation_Abbreviation: PGC ArcticDEM v 4.1
Process_Date: 20250902
Process_Step:
Process_Description:
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.
Process_Step:
Process_Description:
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.
Process_Date: 20250907
Process_Step:
Process_Description:
Interpolate a one-meter resolution seamless elevation surface from input source data and interpolation guides using the Create Elevation Grid tool (triangulation method).
Process_Date: 20250908
Process_Step:
Process_Description:
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.
Process_Date: 20250908
Process_Step:
Process_Description:
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.
Process_Date: 20250908
Process_Step:
Process_Description:
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.
Process_Date: 20250908
Process_Step:
Process_Description:
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.
Process_Date: 20250908
Process_Step:
Process_Description:
Special considerations: A) Vertical datum conversion constants: i) 0 m NAVD88 is -0.802 m above Mean Lower Low Water (at NOAA CO-OPS tide station: 9468756, Nome, Norton Sound AK, via Alaska Tidal Datum Portal). B) Additional vertical transformations: none. B) Interpolation guides: i) Culverts were identified using 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. ii) Inland waterbodies without elevation data were digitized into 3D polygons and assigned depths of one meter below the lowest shoreline elevation.
