First Infrastructure Line Vector, North Carolina (2018-2021)

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Frequently anticipated questions:

What does this data set describe?

Title: First Infrastructure Line Vector, North Carolina (2018-2021)
Abstract:
The U.S. Geological Survey (USGS) supports multiple efforts to understand and predict storm impacts to our nation's coastlines. The first infrastructure line is defined as the seaward boundary of the first row of structures or roads in a coastal area and can be used to assess coastal vulnerability. The first infrastructure line as defined in this dataset represents a cross shore boundary where the most intense hold-the-line management actions are likely to be taken to prevent further landward transgression of the foredune. Certain built features, which often extend far seaward from primary residences and commercial buildings, including boardwalks, swimming pools, gazebos, and sheds, are not included in this first infrastructure line. This dataset is optimized for use in measuring the distance between the first infrastructure line and seaward protective features, particularly coastal dunes. The first infrastructure line in North Carolina (NC) was digitized along the developed ocean-fronting portion of the coastline using imagery/orthomosaics collected by the National Agriculture Imagery Program (NAIP), National Geodetic Survey (NGS), and the Environmental Systems Research Institute (Esri)between 8/26/2018 and 7/16/2021.
  1. How might this data set be cited?
    Seymour, Alexander C., Doran, Kara S., and Palmsten, Margaret L., 20260310, First Infrastructure Line Vector, North Carolina (2018-2021):.

    This is part of the following larger work.

    Seymour, Alexander C., Doran, Kara S., and Palmsten, Margaret L., 20260310, First Infrastructure Line Vector, North Carolina: U.S. Geological Survey data release doi:10.5066/P9GL68X8, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

    Other_Citation_Details: 2026a
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -78.516845
    East_Bounding_Coordinate: -75.461508
    North_Bounding_Coordinate: 36.5496588
    South_Bounding_Coordinate: 33.843362
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 26-Aug-2018
    Ending_Date: 13-Sep-2021
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • String (44)
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 18N
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -75.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.001
      Ordinates (y-coordinates) are specified to the nearest 0.001
      Planar coordinates are specified in meters
      The horizontal datum used is NAD 1983 (NSRS2007).
      The ellipsoid used is GRS 1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
  7. How does the data set describe geographic features?
    NC_First_Infrastructure_Line.shp
    Polyline shapefile of the first infrastructure line for North Carolina. (Source: USGS)
    FID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Coordinates defining the features.
    Shape_Leng
    Length of line segment, in meters. (Source: Esri)
    Range of values
    Minimum:155.610335
    Maximum:45904.093541
    Segment
    First infrastructure line segment identification number, ordered from north to south. (Source: USGS)
    Range of values
    Minimum:1
    Maximum:44
    Source_Img
    Character string representing the publisher of the imagery sources used to digitize the first infrastructure line on a given segment. If multiple sources were used, each were separated by a comma. (Source: USGS)
    ValueDefinition
    ESRIEsri basemap imagery was used to digitize the first infrastructure line segment.
    USDAUSDA NAIP imagery was used to digitize the first infrastructure line segment.
    NGSNOAA NGS imagery used to digitize the first infrastructure line segment.
    State
    Character string representing the state where the segment is found. (Source: USGS)
    ValueDefinition
    North CarolinaThe state where the segment is located.
    Uncy
    A string representing the cross-shore positional uncertainty of the first infrastructure line, in meters. An uncertainty is provided for each imagery source used on a given segment. (Source: USGS) The uncertainty for each source image used separated by a comma. The order of the provided uncertainties follows the order of the source images listed in the Source_Img attribute.

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
    • Margaret L. Palmsten
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center
    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 the seaward boundary of the first infrastructure line as a vector shapefile (.shp). The methods used to digitize these data are described in "Decadal-scale characteristics of natural and anthropogenic dune morphology along North Carolina barrier islands (SE Atlantic coast)" by Seymour and others (2026b) and are also described in the process steps of this metadata record.

How was the data set created?

  1. From what previous works were the data drawn?
    Esri basemap (source 1 of 3)
    North Carolina Center for Geographic Information and Analysis, 20151113, Imagery Hybrid: Esri, ArcGIS Online.

    Online Links:

    Type_of_Source_Media: raster digital data
    Source_Contribution:
    Orthomosaics were used to reference the seaward boundary of the first infrastructure line during manual digitization, and to identify qualifying and non-qualifying structures.
    USDA NAIP imagery (source 2 of 3)
    United States Department of Agriculture National Agriculture Imagery Program, 20191226, 2018 North Carolina NAIP Digital Ortho Photo Imagery: NOAA, Charleston, SC.

    Online Links:

    Type_of_Source_Media: raster digital data
    Source_Contribution:
    Orthomosaics were used to reference the seaward boundary of the first infrastructure line during manual digitization, and to identify qualifying and non-qualifying structures.
    NOAA NGS imagery (source 3 of 3)
    National Oceanic and Atmospheric Administration National Geodetic Survey, 202203, 2020 NOAA NGS Ortho-rectified Color Mosaic Hurricane Florence: NC, SC, and VA: NOAA Office for Coastal Management, National Geodetic Survey, Charleston, SC.

    Online Links:

    Type_of_Source_Media: raster digital data
    Source_Contribution:
    Orthomosaics were used to reference the seaward boundary of the first infrastructure line during manual digitization, and to identify qualifying and non-qualifying structures.
  2. How were the data generated, processed, and modified?
    Date: 01-Nov-2021 (process 1 of 3)
    Several sets of aerial and satellite imagery were used as a reference for this digitizing project, including imagery/orthomosaics from Esri, USDA NAIP, and NOAA NGS. Survey dates for the reference imagery range from 8/26/2018 to 9/13/2021. The imagery set used for a given reach of coast was determined by the available imageries’ perspective, published error, and pixel resolution. A purely nadir perspective (viewing angle directly perpendicular to the earth’s surface) of buildings, or an off-nadir viewing angle that allowed for the seaward facing side of a structure to be visible was required for an image to be used for digitization. Among images that satisfied this perspective requirement, imagery with more constrained horizontal errors and finer pixel resolutions were preferred. Person who carried out this activity:
    Alexander C. Seymour
    U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center
    Physical Scientist
    600 4th Street South
    Saint Petersburg, FL
    United States

    727-502-8122 (voice)
    727-502-8001 (FAX)
    aseymour@usgs.gov
    Data sources used in this process:
    • Esri basemap
    • USDA NAIP imagery
    • NOAA NGS imagery
    Date: 01-Nov-2021 (process 2 of 3)
    Digitization was conducted by a single researcher at 1:1,300 – 1:550 mapping scales in ArcGIS Pro version 2.7. The ArcGIS Pro editor toolbar was used to draw polylines alongshore. The first infrastructure line as defined in this dataset represents a cross-shore boundary where the most intense hold-the-line management actions are likely to be taken to prevent further landward transgression of the foredune. As such, digitization of this line required basic review of state statutes; in this case, the North Carolina Coastal Area Management Act of 1974 (North Carolina Department of Environmental Quality, 1974). According to North Carolina state statute, certain built structures can be classified as “threatened structures”, which can qualify them for elevated levels of protection including geotextile sandbag armoring. However, certain built features which often extend far seaward from primary residences and commercial buildings cannot be designated as “threatened structures”, including boardwalks, swimming pools, gazebos, and sheds. Thus, the aforementioned built features were ignored during digitization. This product was generated to facilitate calculation of coastal resilience metrics, specifically the distance between the dune crest and first infrastructure line. In some circumstances, limited, intermittent coastal retreat can occur among the line of first infrastructure, resulting in isolated clusters of buildings with more seaward positions than immediately adjacent dune crests. To ensure that dune crest/infrastructure distances derived from this data can be sensitive to this condition, we connected alongshore gaps in the first infrastructure line less than 200 m long. This produced negative infrastructure/dune crest distances, which may indicate areas where the primary foredune is infiltrating the first infrastructure line. For more information, please refer to Seymour and others (2026b). Person who carried out this activity:
    Alexander C. Seymour
    U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center
    Physical Scientist
    600 4th Street South
    Saint Petersburg, FL
    United States

    727-502-8122 (voice)
    727-502-8001 (FAX)
    aseymour@usgs.gov
    Date: 19-Dec-2022 (process 3 of 3)
    Uncertainty, source imagery, and state attributes were added to the attribute table of the digitized first infrastructure line segments using ArcGIS Pro's "Add Field" function and manual entry of values. ArcGIS Pro version 2.7 was used for these processes. Person who carried out this activity:
    Alexander C. Seymour
    U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center
    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_First_Infrastructure_Line.shp
  3. What similar or related data should the user be aware of?
    Seymour, Alexander C., Ciarletta, Daniel J., Doran, Kara S., and Palmsten, Margaret L., 20260305, Decadal-scale characteristics of natural and anthropogenic dune morphology along North Carolina barrier islands (SE Atlantic coast): Journal of Coastal Research Unknown.

    Online Links:

    Other_Citation_Details: 2026b
    Stalk, Chelsea A., Morgan, Karen L.M., Brown, Jenna A., and Sherwood, Christopher R., 20200408, Ground Control Point Locations, Elevations and Photographs From North Topsail Beach and Camp Lejeune, North Carolina, June 2019: U.S. Geological Survey data release doi:10.5066/P9R9DPFS, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

    Online Links:

    Brown, Jenna A., Sherwood, Christopher R., Martini, Marinna, Kranenburg, Christine J., and Over, Jin-Si R., 20210408, Ground Control Point Data from the Outer Banks, North Carolina, post-Hurricane Dorian, September 2019: U.S. Geological Survey data release doi:10.5066/P9DVZC23, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

    Online Links:

    North Carolina Department of Environmental Quality, 1974, North Carolina Coastal Area Management Act of 1974: North Carolina Department of Environmental Quality, Raleigh, NC.

    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?
    Cumulative cross shore positional uncertainties of the first infrastructure line are provided for each segment. In this study, cumulative uncertainty is the summation of the georeferencing error of the utilized source imagery, one half of the pixel resolution of the source imagery, and the digitizing error. The National Oceanic Atmospheric Administration (NOAA) NGS imagery georeferencing error is represented by the horizontal error published with the source imagery. The Esri basemap imagery (collected by the North Carolina CGIA) georeferencing error was derived from 11 checkpoints in Onslow Bay, NC and 16 checkpoints in the Northern Outer Banks, NC that were recorded in 2019 and published in two different surveys: Stalk and others (2020); Brown and others (2021). The United States Department of Agriculture (USDA) NAIP imagery georeferencing errors were derived by comparing the positional offset of recognizable and discrete marks (such as tennis court, parking space, and crosswalks) on the ground between the Esri basemap (treated as a control) and NAIP imagery. Twenty-seven marks in Onslow Bay and 15 in the Northern Outer Banks were used for this purpose. NAIP imagery georeferencing errors are the positional offsets from the marks on the control, plus the georeferencing error of the Esri basemap imagery from the respective Onslow Bay or Northern Outer Banks region. The control points recorded in 2019 could not be used to measure the error of the NAIP imagery because not enough control points from the survey were visible in the NAIP imagery. Digitizing errors were derived by re-digitizing an additional first infrastructure line across 20.4 kilometers (km) on Oak Island, NC. The cross-shore distance between the original infrastructure line and the second infrastructure line was recorded at 10 meters (m) alongshore intervals. The digitizing error is the mean of the cross-shore distances recorded on these transects (0.99 m). All editing and calculations were conducted in ArcGIS Pro version 2.7. The final dataset is projected to the North American Datum of 1983 (NAD 1983) National Spatial Reference System (NSRS2007) Universal Transverse Mercator Zone 18 North (UTM 18N) coordinate system.
  3. How accurate are the heights or depths?
  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. Alongshore gaps are present in the first infrastructure line vector where no infrastructure exits within 500 m of the shoreline. 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 None
Use_Constraints Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originators of the data in future products or derivative research.
  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_First_Infrastructure_Line.shp
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, 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 USGS in the use of these data or related materials. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), and have been processed successfully on a computer system at the 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. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein. 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: 10-Mar-2026
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/NC_First_Infrastructure_Line_metadata.faq.html>
Generated by mp version 2.9.51 on Wed Mar 11 16:15:42 2026