Intersects for coastal region of South Carolina generated to calculate short-term shoreline change rates using the Digital Shoreline Analysis System version 5.1

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Frequently anticipated questions:

What does this data set describe?

Intersects for coastal region of South Carolina generated to calculate short-term shoreline change rates using the Digital Shoreline Analysis System version 5.1
The U.S. Geological Survey (USGS) has compiled national shoreline data for more than 20 years to document coastal change and serve the needs of research, management, and the public. Maintaining a record of historical shoreline positions is an effective method to monitor national shoreline evolution over time, enabling scientists to identify areas most susceptible to erosion or accretion. These data can help coastal managers and planners understand which areas of the coast are vulnerable to change.
This data release includes two new mean high water (MHW) shorelines extracted from lidar data collected in 2010 and 2017-2018. Previously published historical shorelines for South Carolina (Kratzmann and others, 2017) were combined with the new lidar shorelines to calculate long-term (up to 166 years) and short-term (up to 18 years) rates of change. Files associated with the long-term and short-term rates are appended with "LT" and "ST", respectively. A proxy-datum bias reference line that accounts for the positional difference in a proxy shoreline (e.g. High Water Line (HWL) shoreline) and a datum shoreline (e.g. MHW shoreline) is also included in this release.
  1. How might this data set be cited?
    Bartlett, Marie K., 20230815, Intersects for coastal region of South Carolina generated to calculate short-term shoreline change rates using the Digital Shoreline Analysis System version 5.1: data release doi:10.5066/P9LLAZYE, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Bartlett, Marie K., Farris, Amy S., and Weber, Kathryn M., 2023, USGS National Shoreline Change — A GIS compilation of new lidar-derived shorelines (2010, 2017, and 2018) and associated shoreline change data for coastal South Carolina: data release doi:10.5066/P9LLAZYE, U.S. Geological Survey, Reston, VA.

    Online Links:

    Bartlett, M.K., Farris, A.S., and Weber, K.M., 2023, USGS National Shoreline Change — A GIS compilation of new lidar-derived shorelines (2010, 2017, and 2018) and associated shoreline change data for coastal South Carolina: U.S. Geological Survey data release,
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -80.876393
    East_Bounding_Coordinate: -78.554070
    North_Bounding_Coordinate: 32.081482
    South_Bounding_Coordinate: 33.848903
  3. What does it look like? (JPEG)
    Map view of dataset
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2000
    Ending_Date: 2018
    ground condition at the time of shoreline source data
  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):
      • Entity point (15170)
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 17
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -81.0
      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 0.6096
      Ordinates (y-coordinates) are specified to the nearest 0.6096
      Planar coordinates are specified in meters
      The horizontal datum used is WGS_1984.
      The ellipsoid used is WGS_84.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
  7. How does the data set describe geographic features?
    The intersection points are generated by DSAS where each DSAS generated transect crosses a shoreline. These intersections represent the shoreline position and contain the data necessary for DSAS to compute short-term rates. Because only modern, MHW lidar shorelines were used to calculate short-term rates, the proxy-datum bias calculation does not apply. (Source: U.S. Geological Survey (USGS))
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Feature geometry. (Source: Esri) Feature geometry. Intersects are point shapefiles.
    Assigned by DSAS based on ordering of transects along the baseline. Used to allow user to sort transect data along the baseline from baseline start to baseline end. (Source: USGS)
    Range of values
    Values in this field correlate to the baseline attribute field ID and are assigned by DSAS to identify the baseline segment used to generate the measurement transect. Baseline segments assigned an ID = 0 are ignored by DSAS and no transects will be cast along those line segments. (Source: USGS)
    Range of values
    Date of shoreline position; date of survey as determined from shoreline layer. (Source: USGS) Date of the shoreline in mm/dd/yyyy
    The distance in meters between the DSAS reference baseline and the shoreline intersection point along a DSAS transect. Decimal values may be positive or negative, which is used to indicate landward (negative) or seaward (positive) shoreline movement. (Source: USGS)
    Range of values
    The easting or X-coordinate location of the intersect point in WGS84 UTM17N. (Source: USGS)
    Range of values
    The northing or Y-coordinate location of the intersect point in WGS84 UTM17N. (Source: USGS)
    Range of values
    The uncertainty of the shoreline intersect point as defined by the positional uncertainty value of the shoreline. (Source: USGS)
    Range of values
    The entity and attribute information provided here describes the tabular data associated with the intersects needed to calculate short-term (approximately 18 years) shoreline change rates. Please review the individual attribute descriptions for detailed information. All calculations for length are in meter units and were based on the UTM zone 17N WGS 84 projection.
    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)
    • Marie K. Bartlett
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Marie K. Bartlett
    U.S. Geological Survey
    384 Woods Hole Rd
    Woods Hole, MA

    508-457-8700 x2306 (voice)

Why was the data set created?

This dataset consists of point data which are created by the Digital Shoreline Analysis System (DSAS) version v5.1 at the intersection of shoreline and transect locations. Measurement transects are cast by DSAS from the baseline to intersect shoreline vectors, and the intersect data provide location and time information used to calculate rates of change. These point data contain identification information related to the DSAS transect (TransOrder) as well as the shoreline (ShorelineID, Uncertainty) and proxy-datum bias data (if applicable). They can be used to visually display which shorelines were used in the rate calculations and capture details on the shoreline represented by the intersection. The distances between the reference baseline and each shoreline intersection along a transect are used by the DSAS software to compute the shoreline change metrics.

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: 2022 (process 1 of 3)
    MHW shorelines (2000-2018), the short-term subset of shorelines used for ST rate calculations, were exported from SC_shorelines and renamed SC_shorelines_ST. Short-term transect features were generated in a personal geodatabase using DSAS v5.1.2020.0720.0030. Parameters Used: baseline layer = SC_baseline, baseline group field = NULL, shoreline layer = SC_shorelines_ST, transect spacing = 50 meters, search distance = 200 meters, land direction = right, shoreline intersection = seaward, File produced = SC_transects_ST. Some transects were manually edited for length, moved, or deleted in an edit session using standard editing tools in the editor toolbar, in ArcMap v10.7.1 For additional details on these parameters, please see the DSAS help file distributed with the DSAS software, or visit the USGS website at:
    Date: 08-Dec-2022 (process 2 of 3)
    Short-term rate calculations were performed without a proxy-datum bias correction which was unnecessary, since only datum-based MHW shorelines (2000-2018) were used. Parameters Used: shoreline layer= SC_shorelines_ST, shoreline date field = Date_, shoreline uncertainty field name = Uncy, the default accuracy = 5.1 meters, shoreline intersection = seaward, stats calculations = [LRR], [EPR], shoreline threshold = 2, confidence interval = 90%. Files produced = SC_trans_ST_rates_20230802_102308, SC_trans_ST_intersect_20230802_102308.
    Date: 2023 (process 3 of 3)
    The intersect feature classes were exported to a shapefile in ArcMap v10.7.1 by right-clicking the transect layer > data > export data. Coordinate system: UTM Zone 17N (WGS84).
  3. What similar or related data should the user be aware of?
    Himmelstoss, Emily A., Farris, Amy S., Henderson, Rachel E., Kratzmann, Meredith G., Ergul, Ayhan, Zhang, Ouya, Zichichi, Jessica L., and Thieler, E. Robert, 2021, Digital Shoreline Analysis System (version 5.1): U.S. Geological Survey Software: software release version 5.1, U.S. Geological Survey, Reston, VA.

    Online Links:

    Use the first two links to access the software. The third link directs to the DSAS project page. Current version of software at time of use was 5.1.
    Himmelstoss, Emily A., Henderson, Rachel E., Kratzmann, Meredith G., and Farris, Amy S., 20211019, Digital Shoreline Analysis System (version 5.1) User Guide: Open-File Report 2021-1091, U.S. Geological Survey, Reston, VA.

    Online Links:

    Refer to the DSAS user guide for more information about attribute requirements, accuracy reports, and feature creation.
    Himmelstoss, Emily A., Kraztmann, Meredith G., and Thieler, E. Robert, 2012, National assessment of shoreline change—Summary statistics for updated vector shorelines and associated shoreline change data for the Gulf of Mexico and Southeast Atlantic coasts: Open-File Report 2017-1015, U.S. Geological Survey, Reston, VA.

    Online Links:

    Kratzmann, Meredith G., Himmelstoss, Emily A., and Thieler, E. Robert, 2017, National assessment of shoreline change – A GIS compilation of updated vector shorelines and associated shoreline change data for the Southeast Atlantic Coast: data release 2017, U.S. Geological Survey, Reston, VA.

    Online Links:

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

  1. How well have the observations been checked?
    The attributes of this dataset are based on the field requirements of the Digital Shoreline Analysis System and were automatically generated by the software during the generation of the intersects layer.
  2. How accurate are the geographic locations?
    The intersection points represent the location where transects cast by the Digital Shoreline Analysis System (DSAS) software crosses a historical shoreline position. The positional uncertainties associated with the shoreline and intersection points are captured in the shoreline attribute table (see larger work citation, SC_shoreline_2010 and SC_shoreline_2017_2018). See Kratzmann and others, 2017, cross-referenced in this metadata file, for uncertainties associated with the historical (2000) shoreline position.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This dataset contains the intersects automatically generated by the DSAS software application that were used to calculate shoreline change rates for the region.
  5. How consistent are the relationships among the observations, including topology?
    TThese data were generated using DSAS v5.1, an automated software program, which does not perform checks for fidelity of the input features. Following generation of the rates and intersects by the DSAS software, a visual inspection of the intersects was performed in map view to determine that no unwanted measurements, such as those crossing man-made coastal structures, were included in the desired long-term (LT) or short-term (ST) shoreline change analysis. It is possible that a small (centimeter-scale) offset may occur when projecting from outside of the spatial reference system used for analysis (UTM Zone 17N WGS84). This is an ArcGIS projection issue; rate data are unaffected.

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 to be used for navigation.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey
    Attn: USGS ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    United States

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? The dataset contains the point data representing the intersection of South Carolina shorelines and transect data (SC_intersects_ST.shp and other shapefile components), browse graphic (SC_intersects_ST_browse.JPG), and the FGDC CSDGM metadata in XML format.
  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?

Last modified: 15-Aug-2023
Metadata author:
Marie K. Bartlett
U.S. Geological Survey
384 Woods Hole Rd
Woods Hole, MA

508-548-8700 x2306 (voice)
The metadata contact email address is a generic address in the event the person is no longer with USGS.
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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