Intersects for the coastal region of Virginia generated to calculate long-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?

Title:
Intersects for the coastal region of Virginia generated to calculate long-term shoreline change rates using the Digital Shoreline Analysis System version 5.1
Abstract:
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 a compilation of previously published historical shoreline positions for Virginia spanning 148 years (1849-1997), and two new mean high water (MHW) shorelines extracted from lidar data collected in 2010 and 2017. These data provide a standardized shoreline database for the state. This release includes both long-term (up to 168 years) and short term (~20 years) rates. 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., 20230526, Intersects for the coastal region of Virginia generated to calculate long-term shoreline change rates using the Digital Shoreline Analysis System version 5.1: data release doi:10.5066/P9DHOFXU, 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., Henderson, Rachel E., and Farris, Amy S., 2023, USGS National Shoreline Change — A GIS compilation of vector shorelines and associated shoreline change data for coastal Virginia from the 1840s to 2010s: data release doi:10.5066/P9DHOFXU, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Bartlett, M.K., Henderson R.E., and Farris, A.S., 2023, USGS National Shoreline Change — A GIS compilation of vector shorelines and associated shoreline change data for coastal Virginia from the 1840s to 2010s: U.S. Geological Survey data release, https://doi.org/10.5066/P9DHOFXU.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -76.0664
    East_Bounding_Coordinate: -75.2373
    North_Bounding_Coordinate: 38.0273
    South_Bounding_Coordinate: 36.5490
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/641c6d69d34e807d39b643db?name=VA_intersects_LT_browse.JPG (JPEG)
    Map view of dataset
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date:
    Ending_Date: 2017
    Currentness_Reference:
    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 (23552)
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 18
      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 0.6096
      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?
    VA_intersects_LT.shp Attribute Table
    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 long-term rates, with and without the proxy-datum bias. (Source: U.S. Geological Survey (USGS))
    FID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Feature geometry. Intersects are point shapefiles.
    TransOrder
    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
    Minimum:1
    Maximum:3672
    BaselineID
    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
    Minimum:1
    Maximum:14
    ShorelineI
    Date of shoreline position; date of survey as determined from shoreline layer. (Source: USGS) Date of the shoreline in mm/dd/yyyy
    Distance
    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) direction from baseline origin. (Source: USGS)
    Range of values
    Minimum:-996.629
    Maximum:2178.12
    Units:meters
    IntersectX
    The easting or X-coordinate location of the intersect point in WGS84 UTM18N. (Source: USGS)
    Range of values
    Minimum:406400.008
    Maximum:478764.615
    IntersectY
    The northing or Y-coordinate location of the intersect point in WGS84 UTM18N. (Source: USGS)
    Range of values
    Minimum:4045351.867
    Maximum:4208872.394
    Uncertaint
    The uncertainty of the shoreline intersect point as defined by the positional-uncertainty value (Uncy_) of the shoreline (ShorelineID). (Source: USGS)
    Range of values
    Minimum:1.301
    Maximum:16.327
    Bias_Dista
    The distance in meters between the DSAS reference baseline and the shoreline intersection point along a DSAS transect with the proxy-datum bias applied. May be positive or negative depending on the orientation of the baseline. (Source: USGS)
    Range of values
    Minimum:-996.629
    Maximum:2193.578
    BIAS
    The estimated unidirectional horizontal offset between the MHW elevation of the lidar data and the HWL shoreline position. (Source: USGS)
    Range of values
    Minimum:0.001
    Maximum:21.737822
    BIAS_X
    The X-coordinate location of the intersect point with the bias applied. (Source: USGS)
    Range of values
    Minimum:406400.008
    Maximum:478772.051
    BIAS_Y
    The Y-coordinate location of the intersect point with the bias applied. (Source: USGS)
    Range of values
    Minimum:4045353.489
    Maximum:4208869.688
    Bias_Uncer
    This is an estimate of the uncertainty of the bias corrected shoreline. It is the shoreline uncertainty and the bias uncertainty added in quadrature. (Source: USGS)
    Range of values
    Minimum:1.301
    Maximum:16.327
    Entity_and_Attribute_Overview:
    The entity and attribute information provided here describes the tabular data associated with the intersects needed to calculate long-term (greater than 50 years, and typically closer to 100 years). Please review the individual attribute descriptions for detailed information. All calculations for length are in meter units and were based on the UTM zone 18N WGS 84 projection. This region has two shapefiles describing intersects, long-term and short-term (see the larger work citation).
    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
    Geologist
    384 Woods Hole Rd
    Woods Hole, MA

    508-457-8700 x2306 (voice)
    mbartlett@usgs.gov

Why was the data set created?

This dataset consists of point data created by the Digital Shoreline Analysis System (DSAS) 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 and 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 4)
    A polyline, midshore baseline was constructed using standard feature creation tools in Esri's ArcMap v10.7.1. The baseline was positioned to follow the overall orientation of the shorelines alongshore (see larger work citation, VA_baseline.shp, VA_shorelines.shp). This was done so that the transects, which are generated by the DSAS software and extend from the baseline, would intersect roughly perpendicular to the general trend of the shorelines. The baseline was constructed in UTM Zone 18N (WGS 84) coordinate system. This process step and all subsequent process steps were performed by the same person - Marie K. Bartlett Person who carried out this activity:
    Marie K. Bartlett
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x 2306 (voice)
    mbartlett@usgs.gov
    Date: 2022 (process 2 of 4)
    Transect features were generated in a personal geodatabase using DSAS v5.1.2020.0720.0030. Parameters Used: baseline layer = VA_baseline, baseline group field = NULL, shoreline layer = VA_shorelines, transect spacing = 50 meters, search distance = 1000 meters, land direction = right, shoreline intersection=seaward, File produced = VA_trans_LT. Some transects were manually edited for length, moved, or deleted in an edit session using standard editing tools 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: https://woodshole.er.usgs.gov/project-pages/DSAS/.
    Date: 2023 (process 3 of 4)
    Shoreline intersects and rate calculations were performed for long-term (LT) rates with and without bias. Parameters Used: shoreline layer = VA_shorelines, shoreline date field = Date_, shoreline uncertainty field name = Uncy_, the default accuracy = 5.1 meters, shoreline intersection=seaward, stats calculations = [LRR], shoreline threshold = 3, confidence interval = 90%. Files produced = VA_trans_LT_rates_20230321_135326, VA_trans_LT_intersect_20230321_135326. The shoreline database contains both MHW and HWL shorelines thus a proxy-datum bias (PDB), stored as a line feature class appended to the reference baseline, is applied during rate calculation. For more information about the origin of the PDB see Ruggiero and List (2009). Rate statistics are presented with and without the PDB applied, denoted in the attribute field with “NB_” or “No bias”. The bias uncertainty values and location data are stored within the bias feature attribute table and the intersects attribute table.
    Date: 2023 (process 4 of 4)
    The intersect feature classes were exported to shapefiles in ArcMap v10.7.1 by right-clicking the transect layer > data > export data. Coordinate System: UTM Zone 18N (WGS84)
  3. What similar or related data should the user be aware of?
    Hapke, Cheryl J., Himmelstoss, Emily A., Kraztmann, Meredith G., List, Jeffrey H., and Thieler, E. Robert, 20120423, National Assessment of Shoreline Change: Historical Shoreline Change along the New England and Mid-Atlantic Coasts: Open-File Report 2010-1118, U.S. Geological Survey, Reston, VA.

    Online Links:

    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:

    Other_Citation_Details:
    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:

    Other_Citation_Details:
    Refer to the DSAS user guide for more information about attribute requirements, accuracy reports, and feature creation.
    Ruggiero, Peter, and List, Jeffrey H., 200909, Improving Accuracy and Statistical Reliability of Shoreline Position and Change Rate Estimates: Journal of Coastal Research vol. 255, Coastal Education and Research Foundation, n/a.

    Online Links:

    Other_Citation_Details: ppg. 1069-1081

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.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This dataset contains the transects automatically generated by the DSAS software application that were used to calculate shoreline change rates for the region. Additional transects may have been generated but did not intersect the minimum requirement of three shorelines. Shoreline change rates data are provided where there are available shorelines to compute change metrics. Though the full database of shorelines was utilized (1849-2017), gaps in shorelines or lack of lidar data in certain areas may mean that not all transects will incorporate every shoreline date in the rate calculations.
  5. How consistent are the relationships among the observations, including topology?
    These 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 were included in the desired long-term (LT) or short-term (ST) shoreline change analysis.

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)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? The dataset contains the point data representing the intersection of Virginia shorelines and transect data (VA_intersects_LT.shp and other shapefile components), browse graphic (VA_intersects_LT_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?
    • Availability in digital form:
      Data format: These files (.cpg, .dbf, .prj, .sbn, .sbx, .shp, and .shx) are a collection of files with a common filename prefix and must be downloaded and stored in the same directory. Together they are the components of the shapefile. Additional files of the same name included are FGDC CSDGM-compliant metadata in XML format. in format Shapefile (version ArcGIS 10.7.1) Esri Point Shapefile Size: 1.4
      Network links: https://www.sciencebase.gov/catalog/item/641c6d69d34e807d39b643db
    • Cost to order the data: None.

Who wrote the metadata?

Dates:
Last modified: 26-May-2023
Metadata author:
Marie K. Bartlett
U.S. Geological Survey
384 Woods Hole Rd
Woods Hole, MA
USA

508-548-8700 x2306 (voice)
whsc_data_contact@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P9DHOFXU/VA_intersects_LT.faq.html>
Generated by mp version 2.9.51 on Sun May 28 18:02:41 2023