Intersect points used to calculate short-term (1980s-2010s) shoreline change rates for the Long Island Sound coastal region using the Digital Shoreline Analysis System version 5.1

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Frequently anticipated questions:

What does this data set describe?

Title:
Intersect points used to calculate short-term (1980s-2010s) shoreline change rates for the Long Island Sound coastal region using the Digital Shoreline Analysis System version 5.1
Abstract:
The U.S. Geological Survey (USGS) maintains shoreline positions for the United States coasts from various historical sources, such as aerial photographs or topographic surveys, and contemporary sources, such as lidar-point clouds and digital elevation models. Shorelines are compiled in a GIS and analyzed in the USGS Digital Shoreline Analysis System (DSAS) software to calculate rates of change. Keeping a record of historical shoreline positions is an effective method to monitor change over time, enabling scientists to identify areas most susceptible to erosion or accretion. These data can help coastal managers understand which areas of the coast are vulnerable to change. This data release, and other associated products, represents an expansion of the USGS national-scale shoreline database to include Long Island Sound (LIS) covering coastal areas in New York and Connecticut. The shoreline positions and shoreline change rates provide actionable information to homeowners, coastal communities, and managers of public and private properties to improve resiliency for coastal hazards in Long Island Sound.
  1. How might this data set be cited?
    Henderson, Rachel E., and Kratzmann, Meredith G., 20250922, Intersect points used to calculate short-term (1980s-2010s) shoreline change rates for the Long Island Sound coastal region using the Digital Shoreline Analysis System version 5.1: data release DOI:10.5066/P1TKEDFX, 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.

    Henderson, Rachel E., Kratzmann, Meredith G., Farris, Amy S., Lentz, Erika E., and Himmelstoss, Emily A., 2025, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2010s for the coast of Long Island Sound, New York and Connecticut: data release DOI:10.5066/P1TKEDFX, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    suggested citation: Henderson, R.E., Kratzmann, M.G., Farris, A.S., Lentz, E.E., and Himmelstoss, E.A., 2025, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2010s for the coast of Long Island Sound, New York and Connecticut: U.S. Geological Survey data release, https://doi.org/10.5066/P1TKEDFX
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -73.817326
    East_Bounding_Coordinate: -71.861418
    North_Bounding_Coordinate: 41.342283
    South_Bounding_Coordinate: 40.799049
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/67bfb14cd34e8876fcbfc9d7?name=LIS_intersects_ST.jpg&allowOpen=true (JPEG)
    Map view of data, purple markers indicate the linear extent of intersect data for short-term calculations of shoreline change.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2025
    Currentness_Reference:
    publication date
  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 (25075)
    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 0.0000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.
  7. How does the data set describe geographic features?
    LIS_intersects_ST.shp
    The intersection points are generated by DSAS where each DSAS generated transect crosses a shoreline. These intersection points represent the shorelines used to compute short-term (ST) rates in Long Island Sound (LIS). (Source: U.S. Geological Survey)
    FID
    Internal feature number used as a unique identifier of an object within a table primarily used in shapefiles. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Feature type.
    TransectID
    The TransectID relates directly to the original transect file Object Identifier, ObjectID or OID (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:6335
    TransOrder
    Assigned by DSAS based on ordering of transects along the baseline. Used to sort transect data along the baseline from baseline start to baseline end. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:6335
    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: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:64
    ShorelineI
    Date of shoreline position; date of survey as determined from shoreline layer. (Source: U.S. Geological Survey) 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. As the LIS baseline is offshore, all values will be negative. (Source: U.S. Geological Survey)
    Range of values
    Minimum:-338.384045
    Maximum:-17.070745
    Units:meters
    IntersectX
    The X-coordinate location in eastings of the intersect point in NAD83 UTM 18N. (Source: U.S. Geological Survey)
    Range of values
    Minimum:599688.617009
    Maximum:762677.666469
    Units:meters
    IntersectY
    The Y-coordinate location in northings of the intersect point in NAD83 UTM 18N. (Source: U.S. Geological Survey)
    Range of values
    Minimum:4517198.35671
    Maximum:4581343.55644
    Units:meters
    Uncertaint
    The uncertainty of the shoreline position represented by the intersect point, as defined by the positional uncertainty attribute value (Uncy) of the shoreline dataset. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.57
    Maximum:5.1
    Entity_and_Attribute_Overview:
    The entity and attribute information provided here describes the tabular data associated with the intersects needed to calculate short-term (ST) shoreline change rates for Long Island Sound (LIS). 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 NAD 83 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)
    • Rachel E. Henderson
    • Meredith G. Kratzmann
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Rachel E. Henderson
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    rehenderson@usgs.gov

Why was the data set created?

This dataset consists of point data which are created by the Digital Shoreline Analysis System (DSAS) version 5.1 at the intersection of shoreline and transect locations for the Long Island Sound coastal region. A reference baseline was used as the originating point for the orthogonal transects cast by the DSAS software. These point data contain identification information related to the DSAS transect (TransectID, TransOrder) as well as the shoreline (ShorelineID [date], Uncertainty). 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.

How was the data set created?

  1. From what previous works were the data drawn?
    LIS_baseline (source 1 of 2)
    Henderson, Rachel E., and Kratzmann, Meredith G., 2025, Baseline for the Long Island Sound coastal region generated to calculate shoreline change rates using the Digital Shoreline Analysis System version 5.1 in Henderson, R.E., Kratzmann, M.G., Farris, A.S., Lentz, E.E., and Himmelstoss, E.A., 2025, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2010s for the coast of Long Island Sound, New York and Connecticut: U.S. Geological Survey data release, https://doi.org/10.5066/P1TKEDFX: data release DOI:10.5066/P1TKEDFX, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details:
    The first link is to the larger work, the second is to the baseline dataset.
    Type_of_Source_Media: digital data
    Source_Contribution:
    Baseline segments (part of this same data release https://doi.org/10.5066/P1TKEDFX) are used by DSAS to cast transects from which shoreline changes can be measured.
    LIS_shorelines (source 2 of 2)
    Henderson, Rachel E., and Kratzmann, Meredith G., 2025, Shorelines for the Long Island Sound coastal region used in shoreline change analysis: Connecticut (1883-2016) and New York (1931-2014) in Henderson, R.E., Kratzmann, M.G., Farris, A.S., Lentz, E.E., and Himmelstoss, E.A., 2025, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2010s for the coast of Long Island Sound, New York and Connecticut: U.S. Geological Survey data release, https://doi.org/10.5066/P1TKEDFX: data release DOI:10.5066/P1TKEDFX, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details:
    The first link is to the larger work, the second is to the shorelines dataset.
    Type_of_Source_Media: digital data
    Source_Contribution:
    Shoreline data for Long Island Sound (part of this same data release https://doi.org/10.5066/P1TKEDFX). Note the range of shoreline dates will vary by location.
  2. How were the data generated, processed, and modified?
    Date: 2025 (process 1 of 6)
    Overview of the workflow used to calculate shoreline change rates and intersection points as part of the Long Island Sound (LIS) shoreline change analysis using DSAS v5.1: 1) Transects were created at 50 meter spacing along shore using a manually created baseline, and shorelines compiled for Long Island Sound (see source citations); 2) Transect features and shorelines were used to generate shoreline intersection points and calculate rates of change; 3) Manual edits performed; 4) Data exported to shapefiles and; 5) Data updated to geographic WGS. Unless otherwise noted, process steps were performed by Rachel E. Henderson. Person who carried out this activity:
    Rachel E. Henderson
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    rehenderson@usgs.gov
    Date: 2025 (process 2 of 6)
    1) DSAS v5.1 was used to create interim transect features (stored in a personal geodatabase) to calculate short-term (ST) shoreline change . DSAS input parameters used: shoreline layer = LIS_Shorelines, baseline layer= LIS_Baseline, baseline group field=DSAS_group, transect spacing=50 meters, search distance=300 meters, shoreline intersection=seaward. Files produced and saved to personal geodatabase = LIS_Trans_ST. Some transects were manually edited for length, moved, or deleted in an edit session using standard editing tools in ArcMap v10.8.2. For additional details on these parameters, please see the DSAS User Guide or visit the USGS website at: https://www.usgs.gov/centers/whcmsc/science/digital-shoreline-analysis-system-dsas. Data sources used in this process:
    • LIS_baseline
    • LIS_shorelines
    Data sources produced in this process:
    • LIS_Trans_ST
    Date: 2025 (process 3 of 6)
    2) Short-term (ST) shoreline change rate calculations performed for Long Island Sound (LIS): To calculate short-term shoreline change rates, shorelines from the years 1984 to 2016 (NY: 1984-2014, 30 years; CT: 1984-2016, 32 years) were utilized with the DSAS generated transects to create shoreline intersect points and shoreline change calculations stored as rate transects. Depending on the available data, the shoreline intersects used for analysis may include those referenced to the datum-based mean high water (MHW), or a proxy-based feature such as the high water line (HWL) or wet-dry line (WDL). Input parameters used: shoreline layer= LIS_Shorelines, shoreline date field=Date_, shoreline uncertainty field name=Uncy, the default accuracy=10 meters, shoreline intersection=seaward, transect layer= LIS_Trans_ST, stats calculations=all, shoreline threshold=0, confidence interval=90%. Files produced and saved to personal geodatabase = LIS_Trans_ST_rates, LIS_Trans_ST_intersects.
    NOTE: All shorelines have an uncertainty value listed in the attribute table that provides the horizontal uncertainty associated with the shoreline, regardless of the method used. The shoreline database contains both MHW and HWL shorelines.
    For additional information, please see the DSAS help file distributed with the DSAS software, or visit the USGS website at: https://www.usgs.gov/centers/whcmsc/science/digital-shoreline-analysis-system-dsas Data sources used in this process:
    • LIS_Trans_ST
    • LIS_shorelines
    Data sources produced in this process:
    • LIS_Trans_ST_rates
    • LIS_Trans_ST_intersects
    Date: 2025 (process 4 of 6)
    3) Manual editing with Google Earth and other orthophoto mosaics were used to identify areas of sandy shoreline and remove transects/intersects (using basic ArcMap editing tools) from analysis in areas of rocky or bedrock coastlines, and some areas with significant anthropogenic modification. Data sources used in this process:
    • LIS_Trans_ST_intersects
    Data sources produced in this process:
    • LIS_Trans_ST_intersects
    Date: 2025 (process 5 of 6)
    4) The intersect feature classes were exported to shapefiles in ArcMap v10.8 by right-clicking the transect layer > data > export data. File renamed LIS_intersects_ST. Data sources used in this process:
    • LIS_Trans_ST_intersects
    Data sources produced in this process:
    • LIS_intersects_ST
    Date: 2025 (process 6 of 6)
    5) The exported intersect shapefile was projected in ArcGIS Pro v3.5.57366 > Geoprocessing > Data Management Tools > Project. Parameters: input projection -NAD83 UTM zone 18N; output projection- geographic coordinates (WGS 84); transformation = WGS_1984_(ITRF00)_To_NAD_1983. Person who carried out this activity:
    Meredith G. Kratzmann
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    mkratzmann@contractor.usgs.gov
  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:

    Other_Citation_Details:
    Use the first link to access the version of the software used (v5.1). The second link is to the current version of DSAS (v6.0). The third link directs to the DSAS project page.
    Himmelstoss, Emily A., Henderson, Rachel E., Kratzmann, Meredith G., and Farris, Amy S., 2021, 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:
    Use the first link to access the user guide. The second link directs to the DSAS project page.

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 cross a historical shoreline position. 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.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This dataset contains all the shoreline/transect intersects used to compute rates in the DSAS v5.1 software application.
  5. How consistent are the relationships among the observations, including topology?
    These data were generated using DSAS, 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- or short-term) 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 No access constraints. Please see 'Distribution Information' for details.
Use_Constraints These data are marked with a Creative Commons 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.These data were automatically generated using the DSAS v5.1 software application. 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 - GS 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 intersections used for the analysis of shoreline data (SHP and other shapefile components), browse graphic, and the FGDC CSDGM metadata.
  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. 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.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data are available in a point shapefile format. The user must have software to read and process the data components of a shapefile.

Who wrote the metadata?

Dates:
Last modified: 22-Sep-2025
Metadata author:
Meredith G. Kratzmann
U.S. Geological Survey
384 Woods Hole Road
Woods Hole, MA
USA

508-548-8700 (voice)
508-457-2310 (FAX)
whsc_data_contact@usgs.gov
Contact_Instructions:
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)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P1TKEDFX/LIS_intersects_ST_metadata.faq.html>
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