North Carolina Synthetic Elevation Checkpoints, Complex Version

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Frequently anticipated questions:

What does this data set describe?

Title: North Carolina Synthetic Elevation Checkpoints, Complex Version
Abstract:
The geospatial datasets describe positions, elevations, and uncertainties for synthetic elevation checkpoints generated across the developed coastline of North Carolina. Two datasets are provided as point shapefiles and American Standard Code for Information Interchange (ASCII) tables, and each contains synthetic checkpoints generated using a time series (1996-2018) of digital elevation models (DEMs), a road vector network, and a classified landcover dataset. The first 'simple' dataset contains ~10,000 checkpoints and the second 'complex' dataset contains ~7,000 checkpoints. The latter dataset was derived using more demanding processing settings and as a result, checkpoints are more accurate, but fewer in number. These datasets can be used to validate remotely sensed topographic surveys such as lidar and photogrammetry-derived DEMs and digital surface models (DSMs). The methods used to generate these data followed the process outlined in "Automated Generation of a Synthetic Elevation Checkpoint Network across the North Carolina Coastline, USA" by Seymour and others (2025).
  1. How might this data set be cited?
    Seymour, Alexander C., and Doran, Kara S., 20250509, North Carolina Synthetic Elevation Checkpoints, Complex Version:.

    This is part of the following larger work.

    Seymour, Alexander C., and Doran, Kara S., 20250509, Synthetic Elevation Checkpoints, North Carolina: U.S. Geological Survey data release doi:10.5066/P1HZA84J, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -78.516538
    East_Bounding_Coordinate: -75.462562
    North_Bounding_Coordinate: 36.540132
    South_Bounding_Coordinate: 33.847425
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 09-Oct-1996
    Ending_Date: 02-Oct-2018
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector and tabular digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (6,853)
    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 0.000000001. Longitudes are given to the nearest 0.000000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is NAD 1983 (2011).
      The ellipsoid used is D NAD 1983 2011.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum 1988
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    NC_Synthetic_Checkpoints_GDB.gdb, Synthetic_Complex_NC, Synthetic_Complex_NC_ASCII_Geographic.csv
    File geodatabase feature class (.gdb) and comma-separated values file (.csv) of the synthetic elevation checkpoints for North Carolina. (Source: USGS)
    OBJECTID
    Internal feature number. This attribute is only present in the feature class dataset. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. This attribute is only present in the feature class dataset. (Source: Esri) Point
    CheckpointID
    An ID for each synthetic elevation checkpoint. The CheckpointID attribute/field is not consecutive because the initial series of checkpoints were winnowed during confidence filtering processes (see Seymour and others, 2025 for details). Some 'simple' and 'complex' checkpoints occur at the same location and thus have the same CheckpointID. (Source: USGS)
    Range of values
    Minimum:67
    Maximum:39,888
    CheckpointElevation
    The elevation of the synthetic checkpoint, in meters (NAVD 88). 'Simple' and 'complex' checkpoints with the same CheckpointID may have different elevations because they underwent different confidence and outlier filtering thresholds (see Seymour and others, 2025 for details). (Source: USGS)
    Range of values
    Minimum:0.466
    Maximum:14.709
    CheckpointElevationCI95
    The 95% confidence interval representing the vertical uncertainty of the synthetic checkpoint elevation, in meters. 'Simple' and 'complex' checkpoints with the same CheckpointID may have different uncertainties because they underwent different confidence and outlier filtering thresholds (see Seymour and others, 2025 for details). (Source: USGS)
    Range of values
    Minimum:0.003
    Maximum:0.039
    ContributingSurveys
    The number of surveys from the time series (see Seymour and others, 2025) that are contributing to the synthetic checkpoint elevation. (Source: USGS)
    Range of values
    Minimum:5
    Maximum:8
    XCoord
    The x-coordinate of the point in meters NAD 1983 (2011). This attribute is only present in the ASCII dataset. (Source: USGS)
    Range of values
    Minimum:-78.5165382
    Maximum:-75.46256239
    YCoord
    The y-coordinate of the point in meters NAD 1983 (2011). This attribute is only present in the ASCII dataset. (Source: USGS)
    Range of values
    Minimum:33.84742532
    Maximum:36.54013189

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Alexander C. Seymour
    • Kara S. Doran
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Kara S. Doran
    600 4th Street South
    Saint Petersburg, FL
    United States

    727-502-8117 (voice)
    727-502-8001 (FAX)
    kdoran@usgs.gov

Why was the data set created?

To provide reference elevations to validate and characterize the accuracy of new and historical remotely-sensed topographic surveys.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 23-Aug-2022 (process 1 of 1)
    Synthetic elevation checkpoints were generated by processing a time series of DEMs, a road vector network, and a classified landcover raster in ArcGIS Pro. Synthetic checkpoints were filtered by a number of quality thresholds and metrics including confidence interval, the presence of elevation trends over time, and a minimum number of contributing surveys. The 'complex' checkpoint version used a more demanding set of quality thresholds and metrics that result in a fewer number of higher accuracy checkpoints than the 'simple' version. The specific details, methods, and parameters used to generate the synthetic elevation checkpoints in this data release can be found in Seymour and others (2025). The 'complex' synthetic checkpoint ASCII table was generated by inputting the point feature class into the 'Feature Class to ASCII' ArcGIS Pro geoprocessing tool. Synthetic checkpoints should not be used to assess the accuracy of elevation datasets that were used to generate the synthetic checkpoints because the independence assumption is violated. See Table 1 and section 2.3 in Seymour and others (2025) for the list of published elevation models that were used to generate the synthetic checkpoints. When validating a digital surface model such as those produced by structure from motion photogrammetry, review section 3.3 and 4.1 of Seymour and others (2025) for considerations on how to best apply synthetic checkpoints. Person who carried out this activity:
    Alexander C. Seymour
    U.S. Geological Survey
    Physical Scientist
    600 4th Street South
    Saint Petersburg, FL
    United States

    727-502-8122 (voice)
    727-502-8001 (FAX)
    aseymour@usgs.gov
    Data sources produced in this process:
    • NC_Synthetic_Checkpoints_GDB.gdb
    • Synthetic_Complex_NC
    • Synthetic_Complex_NC_ASCII_Geographic.csv
  3. What similar or related data should the user be aware of?
    Seymour, Alexander C., Kranenburg, Christine, and Doran, Kara S., 20250507, Automated Generation of a Synthetic Elevation Checkpoint Network across the North Carolina Coastline: SSRN preprint, Elsevier, Online.

    Online Links:

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

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
    Horizontal accuracies were not calculated and are not applicable for these data. Horizontal positions are referenced to the North American Datum of 1983 National Spatial Reference System (2011) (NAD 1983 [2011]) coordinate system.
  3. How accurate are the heights or depths?
    Uncertainties for checkpoint elevations are described by 95% confidence intervals. Confidence intervals are standard diagnostic metrics produced by generalized linear regressions. For more information on how these regressions were calculated, see Seymour and others (2025). Vertical positions are referenced to the North American Vertical Datum of 1988 (Geoid 12B).
  4. Where are the gaps in the data? What is missing?
    This dataset is considered complete for the information presented, as described in the abstract section. 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?
    Uncertainty estimates were produced for all checkpoint elevations. Complex and simple points may have the same CheckpointID, but the elevation and uncertainty estimates differ.

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. Please see 'Distribution Information' for details.
Use_Constraints These data are marked with a Creative Common CC0 1.0 Universal License. These data are in the public domain and do not have any use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
    Attn: USGS SPCMSC Data Management
    600 4th Street South
    Saint Petersburg, FL
    United States

    727-502-8000 (voice)
    gs-g-spcmsc_data_inquiries@usgs.gov
  2. What's the catalog number I need to order this data set? NC_Synthetic_Checkpoints_GDB.gdb, Synthetic_Complex_NC, Synthetic_Complex_NC_ASCII_Geographic.csv
  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. Any use of trade, firm, or product 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?
  5. What hardware or software do I need in order to use the data set?
    The geodatabase feature class and ArcGIS Map Package were created for the use within Esri ArcGIS Pro software (3.0.3 or newer). The ASCII table data were created for the use within Microsoft Excel, or similar text viewers, such as Notepad.

Who wrote the metadata?

Dates:
Last modified: 09-May-2025
Metadata author:
U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
Attn: USGS SPCMSC Data Management
600 4th Street South
Saint Petersburg, FL
United States

727-502-8000 (voice)
gs-g-spcmsc_data_inquiries@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/Synthetic_Complex_NC_Metadata.faq.html>
Generated by mp version 2.9.51 on Fri May 9 09:27:32 2025