Digital Shoreline Analysis System version 4.3 Transects with Short-Term Linear Regression Rate Calculations for central North Carolina (NCcentral)

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Frequently anticipated questions:


What does this data set describe?

Title:
Digital Shoreline Analysis System version 4.3 Transects with Short-Term Linear Regression Rate Calculations for central North Carolina (NCcentral)
Abstract:
Sandy ocean beaches are a popular recreational destination, often surrounded by communities containing valuable real estate. Development is on the rise despite the fact that coastal infrastructure is subjected to flooding and erosion. As a result, there is an increased demand for accurate information regarding past and present shoreline changes. To meet these national needs, the Coastal and Marine Geology Program of the U.S. Geological Survey (USGS) is compiling existing reliable historical shoreline data along open-ocean sandy shores of the conterminous United States and parts of Alaska and Hawaii under the National Assessment of Shoreline Change project. There is no widely accepted standard for analyzing shoreline change. Existing shoreline data measurements and rate calculation methods vary from study to study and prevent combining results into state-wide or regional assessments. The impetus behind the National Assessment project was to develop a standardized method of measuring changes in shoreline position that is consistent from coast to coast. The goal was to facilitate the process of periodically and systematically updating the results in an internally consistent manner.
  1. How might this data set be cited?
    U.S. Geological Survey, 2017, Digital Shoreline Analysis System version 4.3 Transects with Short-Term Linear Regression Rate Calculations for central North Carolina (NCcentral): data release DOI:10.5066/F74X55X7, 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.

    Kratzmann, M.G., Himmelstoss, E.A., and Thieler, E.R., 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 DOI:10.5066/F74X55X7, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -76.570731
    East_Bounding_Coordinate: -75.516217
    North_Bounding_Coordinate: 35.243152
    South_Bounding_Coordinate: 34.583786
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2017
    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 (2323)
    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 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is D_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?
    NCcentral_transects_rates_STlrr
    Transects were automatically generated by DSAS at a 90 degree angle to the user-specified baseline using a smoothing algorithm to maintain roughly parallel transects that are orthogonal with respect to the baseline. (Source: U.S. Geological Survey)
    FID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Coordinates defining the features.
    OBJECTID
    Internal feature number generated for each row of the transect attribute table when stored as a feature class in a geodatabase. This value is the common attribute field when joining to the TransectID value in short-term results output table calculated by DSAS. (Source: U.S. Geological Survey) Sequential unique whole numbers that are automatically generated.
    BaselineID
    Unique identification number of the baseline segment. If BaselineID=0 no transects will be generated. Used by DSAS to determine transect ordering alongshore if multiple baseline segments exist. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:unlimited
    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: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:unlimited
    ProcTime
    Assigned by DSAS automatically to record the date and time a transect was processed. (Source: U.S. Geological Survey)
    Range of values
    Minimum:no value or 0 (when transect was manually created by user)
    Maximum:unlimited (values based on time and date of automatic generation)
    Autogen
    Assigned by DSAS to indicate whether or not a transect was automatically created by DSAS (1= transect was auto generated by DSAS; blank or 0=transect was not auto-generated). (Source: U.S. Geological Survey)
    Range of values
    Minimum:blank or 0
    Maximum:1
    StartX
    Assigned by DSAS automatically to record the X coordinate of the beginning of the transect in meter units (UTM zone 18N, WGS 84). If a transect position has been adjusted during the editing process, the coordinate in the attribute table is not updated automatically. This field was manually updated using Data East XTools v10.2 to reflect the new position of any adjusted transects. (Source: U.S. Geological Survey) Values based on data set extent.
    StartY
    Assigned by DSAS automatically to record the Y coordinate of the beginning of the transect in meter units (UTM zone 18N, WGS 84). If a transect position has been adjusted during the editing process, the coordinate in the attribute table is not updated automatically. This field was manually updated using Data East XTools v10.2 to reflect the new position of any adjusted transects. (Source: U.S. Geological Survey) Values based on data set extent.
    EndX
    Assigned by DSAS automatically to record the X coordinate of the end of the transect in meter units (UTM zone 18N, WGS 84). If a transect position has been adjusted during the editing process, the coordinate in the attribute table is not updated automatically. This field was manually updated using Data East XTools v10.2 to reflect the new position of any adjusted transects. (Source: U.S. Geological Survey) Values based on data set extent.
    EndY
    Assigned by DSAS automatically to record the Y coordinate of the end of the transect in meter units (UTM zone 18N, WGS 84). If a transect position has been adjusted during the editing process, the coordinate in the attribute table is not updated automatically. This field was manually updated using Data East XTools v10.2 to reflect the new position of any adjusted transects. (Source: U.S. Geological Survey) Values based on data set extent.
    Azimuth
    Assigned by DSAS to record the azimuth of the transect measure in degrees clockwise from North. If a transect position has been adjusted during the editing process, the azimuth value in the attribute table is not updated automatically. This field was manually updated using a python script to reflect the new azimuth of any adjusted transects. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:360
    Units:degrees
    SHAPE_Leng
    Length of feature in meter units (UTM zone 18N, WGS 84). (Source: Esri)
    Range of values
    Minimum:883.36203
    Maximum:2346.04328
    Units:meters
    TransectId
    Same value as OBJECTID. Used as a permanent and unique identification number for each transect in the output rates table calculated by DSAS. This attribute was used as the common field when joining the rates table (.dbf) to the transect feature class in a geodatabase. (Source: U.S. Geological Survey) Positive real numbers that are automatically generated.
    LRR
    A linear regression rate-of-change statistic was calculated by fitting a least-squares regression line to all shoreline points for a particular transect. The best-fit regression line is placed so that the sum of the squared residuals (determined by squaring the offset distance of each data point from the regression line and adding the squared residuals together) is minimized. The linear regression rate is the slope of the line. The rate is reported in meters per year with positive values indicating accretion and negative values indicating erosion. (Source: U.S. Geological Survey)
    Range of values
    Minimum:-16.26
    Maximum:15.11
    Units:meters per year
    LR2
    The R-squared statistic, or coefficient of determination, is the percentage of variance in the data that is explained by a regression. It is a dimensionless index that ranges from 1.0 to 0.0 and measures how successfully the best-fit line accounts for variation in the data. The smaller the variability of the residual values around the regression line relative to the overall variability, the better the prediction (and closer the R-squared value is to 1.0). (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:1
    LSE
    The predicted (or estimated) values of y (the distance from baseline in meters) are computed for each shoreline point by using the values of x (the shoreline date) and solving the equation for the best-fit regression line (y=mx+b). The standard error is also called the standard deviation. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:359.98
    Units:meters
    LCI90
    The standard error of the slope with confidence interval describes the uncertainty of the reported rate. The LRR rates are determined by a best-fit regression line for the shoreline data at each transect. The slope of this line is the reported rate of change (in meters/year). The confidence interval (LCI) is calculated by multiplying the standard error (also called the standard deviation) of the slope by the two-tailed test statistic at the user-specified 90 percent confidence. This value is often reported in conjunction with the slope to describe the confidence of the reported rate. For example: LRR = 1.2 LCI90 = 0.7 could be reported as a rate of 1.2 (+/-) 0.7 meters/year. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:126.809
    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. All calculations for length are in meter units and were based on the UTM zone 18N WGS84 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)
    • 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: E.A. Himmelstoss
    384 Woods Hole Road
    Woods Hole, MA
    USA

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

Why was the data set created?

This dataset consists of short-term (~30-year) shoreline change rates for the central North Carolina coastal region from Cape Hatteras to Cape Lookout. Rate calculations were computed within a GIS using the Digital Shoreline Analysis System (DSAS) version 4.3, an ArcGIS extension developed by the U.S. Geological Survey. Short-term rates of shoreline change were calculated using a linear regression rate method where three or more shorelines exist in the dataset for the short-term time period (1960 and later). A reference baseline was used as the originating point for the orthogonal transects cast by the DSAS software. The transects intersect each shoreline establishing measurement points, which are then used to calculate short-term rates.

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: 09-May-2016 (process 1 of 10)
    Transect features generated using DSAS v4.3 in ArcMap v10.2. Parameters Used: baseline layer=NCcentral_baseline, baseline group field=NULL, transect spacing=50 meters, transect length=1800 meters, cast direction=AUTO-DETECT, baseline location=offshore, cast method=smoothed, smoothing distance=2500 meters, flip baselines=not selected. For additional details on these parameters, please see the DSAS help file distributed with the DSAS software, or visit the website at: https://woodshole.er.usgs.gov/project-pages/DSAS/version4/ This process step and all subsequent process steps were performed by the same person: M.G. Kratzmann. Person who carried out this activity:
    M.G. Kratzmann
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    mkratzmann@usgs.gov
    Date: 09-May-2016 (process 2 of 10)
    Some transects were manually edited for length, moved, or deleted in an edit session using standard editing tools in ArcMap v10.2.
    Date: 12-May-2016 (process 3 of 10)
    Rate calculations performed in DSAS v4.3 using ArcMap v10.2 on selected shoreline features only (Select by Attributes, [Year]>=1960) with the following criteria: 1) they contained three or more shorelines required to compute short-term linear regression shoreline change analysis (a shoreline from the 1960s-70s, the modern (lidar-derived or 1990s) shoreline, and at least one other shoreline from the 1960s to present); 2) they contained the two minimum shorelines required to compute short-term end point shoreline change analysis (a shoreline from the 1960s-70s and the modern (lidar-derived or 1990s) shoreline). In NCcentral, the shoreline date range for short-term linear regression rates is 1962 to 2010. Shoreline uncertainty table added to ArcMap project (NCcentral_shorelines_uncertainty.dbf) and used by DSAS to apply bias-correction to distance measurements established by transects. Parameters Used: shoreline layer=NCcentral_shorelines (selected features), shoreline date field=Date_, shoreline uncertainty field name=Uncy, the default uncertainty=5.1 meters, shoreline intersection parameters=closest, stats calculations=[End Point Rate (EPR)], [Linear Regression Rate (LRR)], shoreline threshold=2, confidence interval=90%. Due to shoreline configuration at Cape Lookout, NC, rates were calculated in two sections so that DSAS transects correctly intersected the shorelines. Output rate table names = NCcentral_transects_rates_20160512_110646 (transects 13-140, baseline ID 1) and NCcentral_transects_rates_20160512_122139 (transects 141-2560, baseline ID 2).
    Date: 12-May-2016 (process 4 of 10)
    Shoreline rates tables (NCcentral_transects_rates_20160512_110646.dbf and NCcentral_transects_rates_20160512_122139.dbf) were joined to the corresponding transect feature class in ArcMap v10.2 by right-clicking on the transect layer > joins and relates > join > join attributes from a table. Parameters: join field - OBJECTID; table to join - NCcentral_transects_rates_[TIMESTAMP]; field in table: TransectID; join options - keep only matching records. Process dates are 20160512 and 20160516.
    Date: 12-May-2016 (process 5 of 10)
    Transects containing linear regression rates in each joined feature class were selected and exported to a shapefile, adding A and B to the filenames for each of the two calculations (NCcentral_transects_rates_STlrr_[A or B].shp) in ArcMap v10.2 by right-clicking the transect layer > data > export data, permanently linking the joined rate fields to the transects. Superfluous fields in the linear regression rate shapefiles pertaining to the end point rate method were deleted. Linear regression rates are reported with preference when both rate types exist for a given transect. Process dates are 20160512 and 20160516.
    Date: 16-May-2016 (process 6 of 10)
    Once exported, the files for each section of NCcentral were merged into one shapefile for the linear regression rate method in ArcToolbox (v10.2) > Data Management Tools > General > Merge. Since rates were calculated in two sections, numbering of the OBJECTID and TransectID output fields were not continuous. Values for transects with baseline ID=2 were renumbered in the merged transect shapefile to be continuous.
    Date: 16-May-2016 (process 7 of 10)
    The short-term linear regression rate transects were visually compared with the short-term end point rate transects in an ArcMap session. Each set of transects was assigned a different color and the short-term linear regression rate transects were manually deleted for any stretch of alongshore coast that had fewer than 90% coverage for a 1 kilometer stretch (18 or more transects out of 20 for 50-meter spacing).
    Date: 16-May-2016 (process 8 of 10)
    Any transects that did not cross a lidar shoreline were deleted using standard editing tools in ArcMap v10.2.
    Date: 16-May-2016 (process 9 of 10)
    The edited short-term linear regression rate transect shapefile was projected in Esri's ArcToolbox (v10.2) > Data Management Tools > Projections and Transformations > Project. Parameters: input projection - UTM zone 18N (WGS 84); output projection - geographic coordinates (WGS 84); transformation = none.
    Date: 25-Aug-2017 (process 10 of 10)
    Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Alan O. Allwardt
    Contractor -- Information Specialist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7551 (voice)
    831-427-4748 (FAX)
    aallwardt@usgs.gov
  3. What similar or related data should the user be aware of?
    Morton, Robert A., and Miller, Tara L., 2005, National Assessment of Shoreline Change: Part 2 Historical Shoreline Changes and Associated Coastal Land Loss along the U.S. Southeast Atlantic Coast: Open-File Report 2005-1401, U.S. Geological Survey, Reston, VA.

    Online Links:

    Thieler, E.R., Himmelstoss, E.A., Zichichi, J.L., and Ergul, A., 2009, Digital Shoreline Analysis System (DSAS) version 4.0 - An ArcGIS extension for calculating shoreline change: Open-File Report 2008-1278, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details: Current version of software at time of use was 4.3
    Himmelstoss, E.A., Kratzmann, M.G., and Thieler, E.R., 2017, 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:


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 transect layer or during the calculation of shoreline change rates performed by the software.
  2. How accurate are the geographic locations?
  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 linear regression short-term (~30-year) shoreline change rates for the region. Additional transects may have been generated but did not intersect the shoreline dates specified within the 1 kilometer alongshore length threshold to calculate linear regression short-term rates.
  5. How consistent are the relationships among the observations, including topology?
    These data were generated using DSAS v4.3, an automated software program which does not perform checks for fidelity of the input features. The transects were visually inspected and sometimes manually adjusted within a standard ArcMap edit session to adjust the position at which an individual transect intersected the shorelines.

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
    Denver Federal Center
    Denver, CO
    USA

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set?
  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 a polyline shapefile format. The user must have software to read and process the data components of a shapefile.

Who wrote the metadata?

Dates:
Last modified: 25-Aug-2017
Metadata author:
U.S. Geological Survey
Attn: M.G. Kratzmann
384 Woods Hole Road
Woods Hole, MA
USA

508-548-8700 (voice)
mkratzmann@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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