Uncertainty table for lidar-derived shorelines used when calculating rates in the Digital Shoreline Analysis System software for the north shore of Nantucket, MA

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Frequently anticipated questions:


What does this data set describe?

Title:
Uncertainty table for lidar-derived shorelines used when calculating rates in the Digital Shoreline Analysis System software for the north shore of Nantucket, MA
Abstract:
The Massachusetts Office of Coastal Zone Management launched the Shoreline Change Project in 1989 to identify erosion-prone areas of the coast. The shoreline position and change rate are used to inform management decisions regarding the erosion of coastal resources. In 2001, a 1994 shoreline was added to calculate both long- and short-term shoreline change rates at 40-meter intervals along ocean-facing sections of the Massachusetts coast. In 2013 two oceanfront shorelines for Massachusetts were added using 2008-2009 color aerial orthoimagery and 2007 topographic LIDAR lidar datasets obtained from NOAA's Ocean Service, Coastal Services Center.
This 2018 update includes two new mean high water (MHW) shorelines for the Massachusetts coast extracted from lidar data collected between 2010-2014. The first new shoreline for the state includes data from 2010 along the North Shore and South Coast from lidar data collected by the U.S. Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX). Shorelines along the South Shore and Outer Cape are from 2011 lidar data collected by the U.S. Geological Survey's (USGS) National Geospatial Program Office. Shorelines along Nantucket and Martha’s Vineyard are from a 2012 U.S. Army Corps of Engineers Post Sandy Topographic lidar survey. The second new shoreline for the North Shore, Boston, South Shore, Cape Cod Bay, Outer Cape, South Cape, Nantucket, Martha’s Vineyard, and South Coast west of Buzzards Bay is from 2013-2014 lidar data collected by the U.S. Geological Survey's (USGS) Coastal and Marine Geology Program. Shorelines were extracted from these lidar surveys using several different methods dependent on the location of the shoreline and whether or not wave data were available.
Supplemental_Information:
Cross-referenced citations are applicable to the dataset as a whole. Additional citations are located within individual process steps that pertain specifically to the method described in that step.
  1. How might this data set be cited?
    U.S. Geological Survey, 2018, Uncertainty table for lidar-derived shorelines used when calculating rates in the Digital Shoreline Analysis System software for the north shore of Nantucket, MA: data release DOI:10.5066/P9O7S72B, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Himmelstoss, Emily A., Farris, Amy S., and Weber, Kathryn M., 2018, Massachusetts Shoreline Change Project: A GIS Compilation of Vector Shorelines for the 2018 update: data release DOI:10.5066/P9O7S72B, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Himmelstoss, E.A., Farris, A.S., and Weber, K.M., 2018, Massachusetts shoreline change project—A GIS compilation of vector shorelines for the 2018 update: U.S. Geological Survey data release, https://doi.org/10.5066/P9O7S72B.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.232925
    East_Bounding_Coordinate: -70.023758
    North_Bounding_Coordinate: 41.39199674
    South_Bounding_Coordinate: 41.27563968
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 29-Nov-2013
    Ending_Date: 04-Dec-2013
    Currentness_Reference:
    ground condition of the shorelines on which these values are based
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: tabular digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference:
      This dataset contains 1193 records that are related to the associated shoreline datasets by M-values in each polyline-M shapefile that is represented by the ID attribute in this dataset.
    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 0.0197425918. Longitudes are given to the nearest 0.0261676653. Latitude and longitude values are specified in Decimal seconds. 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?
    Nantucket_pShorelineNB_2013_uncertainty
    uncertainty table (Source: U.S. Geological Survey)
    OID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    ID
    This field is case-sensitive and name specific. The field contains a cross-shore lidar profile ID stored as the M-value (measure value) at each vertex in the calibrated shoreline route. This serves as the link between the lidar shoreline and the uncertainty table and must be a unique number at each point. (Source: U.S. Geological Survey)
    Range of values
    Minimum:7
    Maximum:1510
    UNCY
    This field heading is case-sensitive and name specific. The field contains the plus/minus horizontal uncertainty (meters) in the lidar shoreline position at each cross-shore beach profile. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.67
    Maximum:17.94
    Units:meters
    BIAS
    This field is a place holder and is not used in the north shore of Nantucket analysis. It is a required field for the file when using the Digital Shoreline Analysis System software. This field heading is case-sensitive and name specific. The field contains a proxy-datum bias value describing the unidirectional horizontal offset (in meters) between the MHW elevation of the lidar data and proxy-based historic HWL shoreline positions. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:0
    Units:meters
    UNCYB
    This field is a place holder and is not used in the north shore of Nantucket analysis. It is a required field for the file when using the Digital Shoreline Analysis System software. This field heading is case-sensitive and name specific. The field contains the uncertainty in the calculated proxy-datum bias value (BIAS) in meters. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:0
    Units:meters
    Entity_and_Attribute_Overview:
    The entity and attribute information provided here describes the tabular data associated with the dataset. Please review the individual attribute descriptions for detailed information.
    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)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Emily A. Himmelstoss
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2262 (voice)
    508-547-2310 (FAX)
    ehimmelstoss@usgs.gov

Why was the data set created?

This table includes measurement and positional errors associated with the north shore of Nantucket, Massachusetts. This shoreline does not have buoy data from which to gather wave data, so the run-up equations the profile method implements to estimate a proxy-datum bias value cannot be used. While this table contains columns used to store a proxy-datum bias value (BIAS) and associated uncertainty (UNCYB) these fields do not contain any data and are simply place holders for use in the Digital Shoreline Analysis System software. The only field being used is the positional uncertainty field (UNCY). The dataset contains a common attribute with the M-values stored for the lidar data within the Nantucket_pShorelineNB_2013.shp. These data are used in conjunction with the shoreline file to calculate rates of shoreline change.

How was the data set created?

  1. From what previous works were the data drawn?
    2013-2014 lidar (source 1 of 1)
    Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Office for Coastal Management (OCM), and Woolpert, 20150615, 2013-2014 U.S. Geological Survey CMGP LiDAR: Post Sandy (MA, NH, RI): NOAA's Ocean Service, Office for Coastal Management (OCM), Charleston, SC.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    The bare earth point cloud data in LAS format were used to extract shorelines using methods described in the process steps.
  2. How were the data generated, processed, and modified?
    Date: 2016 (process 1 of 2)
    Whenever possible, a profile method was used to extract the operational Mean High Water (MHW) shoreline from the lidar point cloud data, using a Matlab-based approach (Matlab version 2015b) similar to the one developed by Stockdon and others (2002). Elevation values for the height of MHW were determined from vdatum (version 3.8) provided by NOAA (https://vdatum.noaa.gov/). We continued the practice set out by Weber and others, (2005) of using one MHW value for a continuous section of coast (as opposed to using a continuously varying value). We chose this value such that it is always within 15 cm of the value returned by vdatum at any point along the coast. For example, we used MHW = 0.6 m for all of Buzzards Bay even though vdatum shows it varying slightly over the basin. For the northest facing part of the coast we used an average MHW of 0.45 m. This profile method uses a coast-following reference line with 20 m spaced profiles. All lidar data points that are within 1 m of each profile are associated with that profile. All work is done on the 2 m wide profiles, working on a single profile at a time.
    For each profile, a linear regression was fit through data points on the foreshore and the regression was evaluated at the MHW elevation to yield the cross-shore position of the MHW shoreline. If there was a data gap at MHW or if the MHW elevation was obscured by water points, the linear regression was simply extrapolated to the MHW elevation. Foreshore beach slope is defined as the slope of the regression line.
    Each MHW shoreline point that was extracted using this profile method has an uncertainty associated with it. This uncertainty includes three components: 1) the 95% confidence interval on the linear regression estimate of the shoreline position; 2) the uncertainty associated with the elevation of the raw lidar data and; 3)the uncertainty due to extrapolation. These three components of uncertainty were added in quadrature to yield a total error for each shoreline point. For details on each component, see pp.12-13 under the section titled Lidar-Derived MHW Shoreline Position Uncertainty in Hapke and others (2011).
    There is a known horizontal offset between the datum-based lidar MHW shoreline and the proxy-based historical shorelines on open-ocean sandy beaches that nearly always acts in one direction (Ruggiero and List, 2009). In order to estimate the bias between these two types of shorelines, wave data from a nearby buoy is needed to calculate wave run-up. Many of the sheltered areas within the Massachusetts study area do not have nearby buoy data and a proxy-datum bias value cannot be calculated in these areas. Therefore when this new datum-based MHW shoreline is compared to historic proxy-based HWL shorelines in these sheltered areas, there may be some artificial landward offset of the historic data that has not been quantified and could potentially influence the rates. For example, the north facing shoreline of Martha's Vineyard tends to have lower wave energy, which would result in less run-up and yield a smaller offset between a proxy shoreline and a datum shoreline than would occur along open-ocean coasts. Hapke, C.J., Himmelstoss, E.A., Kratzmann, M.G., List, J.H., and Thieler, E.R., 2011, National assessment of shoreline change—Historical shoreline change along the New England and Mid-Atlantic coasts: U.S. Geological Survey Open-File Report 2010-1118, 57 p., https://pubs.usgs.gov/of/2010/1118/.
    Ruggiero, P., and List, J.H., 2009, Improving accuracy and statistical reliability of shoreline position and change rate estimates: Journal of Coastal Research, v. 25, no. 5, p. 1069-1081. [Also available at https://www.jstor.org/stable/27752753]
    Stockdon, H.F., Sallenger, A.H., List, J.H., and Holman, R.A., 2002, Estimation of shoreline position and change using airborne topographic lidar data: Journal of Coastal Research, v.18, no. 3, p. 502-513. [Also available at https://www.jstor.org/stable/4299097] Person who carried out this activity:
    Amy S. Farris
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2344 (voice)
    508-457-2310 (FAX)
    afarris@usgs.gov
    Date: 2016 (process 2 of 2)
    The series of operational MHW points extracted from the cross-shore lidar profiles were converted to a .dbf file storing the lidar positional uncertainty, for each point of the original lidar data. During the rate calculation process DSAS uses linear referencing to retrieve the uncertainty value stored in the associated table. Person who carried out this activity:
    Emily A. Himmelstoss
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2262 (voice)
    508-457-2310 (FAX)
    ehimmelstoss@usgs.gov
  3. What similar or related data should the user be aware of?
    Thieler, E.R., and Smith, T.L., 2013, Massachusetts Shoreline Change Mapping and Analysis Project, 2012 Update: Open-File Report 2012-1189, U.S. Geological Survey, Reston, VA.

    Online Links:

    Smith, Theresa L., Himmelstoss, Emily A., and Thieler, E. Robert, 2013, Massachusetts Shoreline Change Project: A GIS Compilation of Vector Shorelines and Associated Shoreline Change Data for the 2012 update: Open-File Report 2012-1183, U.S. Geological Survey, Reston, VA.

    Online Links:

    Thieler, E. Robert, O'Connell, James F., and Schupp, Courtney A., 2001, The Massachusetts Shoreline Change Project: 1800s to 1994 Technical Report: U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Himmelstoss, Emily A., Kratzmann, Meredith G., Hapke, Cheryl J., Thieler, E. Robert, and List, Jeffrey, 20110119, The National Assessment of Shoreline Change: A GIS Compilation of Vector Shorelines and Associated Shoreline Change Data for the New England and Mid-Atlantic Coasts: Open-File Report 2010-1119, U.S. Geological Survey, Reston, VA.

    Online Links:

    Himmelstoss, Emily A., Farris, Amy S., Henderson, Rachel E., Kratzmann, Meredith G., Ergul, Ayhan, Zhang, Ouya, and Zichichi, Jessica L., 2018, Digital Shoreline Analysis System (version 5.0): U.S. Geological Survey software: software release version 5.0, 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 in this table record positional and measurement uncertainties and datum offsets calculated during the process of extracting an operational mean high water shoreline from the lidar data as described in the process steps. The field names are based on the requirements for use within the Digital Shoreline Analysis System (DSAS) software (USGS software release).
  2. How accurate are the geographic locations?
    Each MHW shoreline point extracted using the profile method has an uncertainty associated with it. This uncertainty includes three components:
    1) the 95% confidence interval on the linear regression estimate of the shoreline position;
    2) the uncertainty associated with the elevation of the raw lidar data which is stated as 0.1 m RMS in the lidar metadata;
    3) the uncertainty due to extrapolation if the shoreline point was determined by extrapolation.
    The lidar shoreline has an average positional uncertainty of plus or minus 1.76 meters.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    The table only contains data where a mean high water shoreline point could be extrapolated from the lidar.
  5. How consistent are the relationships among the observations, including topology?
    Each row contains data associated with an individual vertex point along the lidar shoreline in Nantucket_pShorelineNB_2013.shp.

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.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    MS 302
    Denver, CO
    USA

    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 uncertainty data in DBF format (Nantucket_pShorelineNB_2013_uncertainty.dbf) and the CSDGM metadata in XML and TEXT 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.
    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?
  5. What hardware or software do I need in order to use the data set?
    These data are available in dBase file format. The user must have software capable of reading or importing the dBase formatted data file.

Who wrote the metadata?

Dates:
Last modified: 30-Oct-2018
Metadata author:
Emily A. Himmelstoss
U.S. Geological Survey
384 Woods Hole Road
Woods Hole, MA
USA

508-548-8700 x2262 (voice)
508-457-2310 (FAX)
ehimmelstoss@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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