Aerial_Shorelines_1940_2015.shp - Dauphin Island, Alabama Shoreline Data Derived from Aerial Imagery from 1940 to 2015

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Frequently anticipated questions:


What does this data set describe?

Title:
Aerial_Shorelines_1940_2015.shp - Dauphin Island, Alabama Shoreline Data Derived from Aerial Imagery from 1940 to 2015
Abstract:
Aerial_WDL_Shorelines.zip features digitized historic shorelines for the Dauphin Island coastline from October 1940 to November 2015. This dataset contains 10 Wet Dry Line (WDL) shorelines separated into 58 shoreline segments alongshore Dauphin Island, AL. The individual sections are divided according to location along the island and shoreline type: open-ocean, back-barrier, marsh shoreline. Imagery of Dauphin Island, Alabama was acquired from several sources including the United States Geological Survey (USGS), the National Agriculture Imagery Program (NAIP), the United States Department of Agriculture's Farm Service Agency (USDA, FSA), and the University of Alabama. These images were downloaded directly from the source's website or received as a hard copy via mail. Using ArcMap 10.3.1, the imagery was used to delineate and digitize historical shorelines at the wet-dry line along sandy beaches and the mean high water line where vegetation indicated. These shorelines were digitized for use in long-term shoreline and wetland analyses and physical change assessments. Shorelines for all 10 dates were compiled into a database for use with the Digital Shoreline Analysis System (DSAS; Thieler and others, 2009) to quantify rates of shoreline change over the 1940-2015 time period. The migration of shorelines through time is presented as the linear regression rate (LRR) in the associated back-barrier and open ocean transect files, which are also included in the USGS data release (https://coastal.er.usgs.gov/data-release/provisional/ip086178/).
  1. How might this data set be cited?
    Nelson, Paul R., Henderson, Rachel E., Smith, Christopher G., and Long, Joseph W., 20170623, Aerial_Shorelines_1940_2015.shp - Dauphin Island, Alabama Shoreline Data Derived from Aerial Imagery from 1940 to 2015: U.S. Geological Survey Data Release doi:10.5066/F7T43RB5, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.344204
    East_Bounding_Coordinate: -88.052726
    North_Bounding_Coordinate: 30.287151
    South_Bounding_Coordinate: 30.192035
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 27-Oct-1940
    Ending_Date: 12-Nov-2015
    Currentness_Reference:
    ground condition
  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 (58)
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 16
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -87.0
      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 Meter
      The horizontal datum used is D_North_American_1983.
      The ellipsoid used is GRS_1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
  7. How does the data set describe geographic features?
    Aerial_Shorelines_1940_2015
    Table containing attribute information associated with the data-set. (Source: USGS)
    Shape
    Feature Geometry (Source: Esri) Coordinates defining the features.
    OBJECTID
    Internal feature number. (Source: Esri)
    Range of values
    Minimum:1
    Maximum:58
    DATE_
    Date imagery was collected for the Dauphin Island coast using the MM/DD/YYYY format. (Source: USGS)
    Range of values
    Minimum:10/27/1940
    Maximum:11/12/2015
    NOTES
    Notes about each shoreline segment, according to 1) location along the island (Dauphin Island, Little Dauphin Island, Pelican Island) and shoreline type (open-ocean, back-barrier, marsh shoreline). (Source: USGS) Additional shoreline information, specific to each line segment.
    UNCERT
    Estimate of shoreline position uncertainty. Actual shoreline position is within the range of this value (plus or minus, meters). (Source: USGS)
    Range of values
    Minimum:7.5
    Maximum:13
    Shape_Leng
    System-generated attribute field, which was automatically created by ArcGIS to indicate the feature length. (Source: Esri)
    Range of values
    Minimum:2622.893684
    Maximum:47110.490534
    Units:Meters
    Entity_and_Attribute_Overview:
    This datasest contains WDL shoreline data extracted from aerial imagery datasets from 1940 to 2015 with associated attributes for use with the Digital Shoreline Analysis System.
    Entity_and_Attribute_Detail_Citation:
    The attributes required for use with DSAS include auto-generated fields - OBJECTID, Shape, Shape_Leng, and user-created fields - DATE_ and UNCERT. The entity and attribute information was generated by the individual and/or agency identified as the originator of the data-set. Please review the rest of the metadata record for additional details and information.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Paul R. Nelson
    • Rachel E. Henderson
    • Christopher G. Smith
    • Joseph W. Long
  2. Who also contributed to the data set?
    Acknowledgment of the U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, as a data source would be appreciated in products developed from these data, and such acknowledgment as is standard for citation and legal practices. Sharing of new data layers developed directly from these data would also be appreciated by the U.S. Geological Survey staff. Users should be aware that comparisons with other datasets for the same area from other time periods may be inaccurate due to inconsistencies resulting from changes in photointerpretation, mapping conventions, and digital processes over time. These data are not legal documents and are not to be used as such.
  3. To whom should users address questions about the data?
    U.S. Geological Survey Coastal and Marine Science Center
    Attn: Paul R. Nelson
    600 4th Street South
    St. Petersburg, FL

    727-502-8127 (voice)
    727-502-8182 (FAX)
    prnelson@usgs.gov

Why was the data set created?

Shoreline data are considered a crucial element in performing change analysis for erosion and accretion studies for tracking shoreline movement over time. Aerial imagery was used to digitize the Dauphin Island coastline to document the short- and long-term changes of the selected study area. The digitized shorelines provide an accurate and measurable change in shape, area, and shoreline movement over a short and long period of time. Shorelines derived from these aerial images provide information about the position of the island through time and are used to quantify the rate of change during this time period. These data will aid in developing an understanding of the evolution of the barrier island position, size and shape as well as documenting spatially-variable patterns in erosion and accretion of different sections of the island.

How was the data set created?

  1. From what previous works were the data drawn?
    Dauphin_1940 (source 1 of 10)
    U.S. Geological Survey (USGS), 19740429, Aerial Single Frame Photos - Dauphin Island 1940: U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota.

    Online Links:

    Other_Citation_Details:
    The Aerial Photography Single Frame Records collection is a large and diverse group of imagery acquired by Federal organizations from 1937 to the present. Over 6.4 million frames of photographic images are available for download as medium and high resolution digital products. The high resolution data provide access to photogrammetric quality scans of aerial photographs with sufficient resolution to reveal landscape detail and to facilitate the interpretability of landscape features. Coverage is predominantly over the United States and includes portions of Central America and Puerto Rico. Individual photographs vary in scale, size, film type, quality, and coverage.
    Type_of_Source_Media: Digital and/or Hardcopy Resources.
    Source_Scale_Denominator: 48000
    Source_Contribution:
    Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
    Dauphin_1952 (source 2 of 10)
    U.S. Geological Survey (USGS), 19750707, Aerial Single Frame Photos - Dauphin Island 1952: U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota.

    Online Links:

    Other_Citation_Details:
    The Aerial Photography Single Frame Records collection is a large and diverse group of imagery acquired by Federal organizations from 1937 to the present. Over 6.4 million frames of photographic images are available for download as medium and high resolution digital products. The high resolution data provide access to photogrammetric quality scans of aerial photographs with sufficient resolution to reveal landscape detail and to facilitate the interpretability of landscape features. Coverage is predominantly over the United States and includes portions of Central America and Puerto Rico. Individual photographs vary in scale, size, film type, quality, and coverage.
    Type_of_Source_Media: Digital and/or Hardcopy Resources
    Source_Scale_Denominator: 69000
    Source_Contribution:
    Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
    Dauphin_1960 (source 3 of 10)
    United States Department of Agriculture - Farm Service Agency, Unknown, Aerial Imagery Mobile County, Alabama, 1960: United States Department of Agriculture - Farm Service Agency, Salt Lake City, Utah.

    Online Links:

    Other_Citation_Details:
    The Aerial Photography Field Office (APFO) has a vast amount of imagery of the United States and its territories from 1955 to the present.
    Type_of_Source_Media: Digital and/or Hardcopy Resources
    Source_Scale_Denominator: 20000
    Source_Contribution:
    Imagery provided by USDA-FSA as high-resolution scans(.tif) on hard disk via post. Imagery was georectified and then used to delineate and digitize shoreline positions.
    Dauphin_1974 (source 4 of 10)
    Geological Survey of Alabama - Acquired from University of Alabama's Cartographic Research Laboratory., Unknown, Aerial Photography Mobile County, Alabama, 1974: Cartographic Research Laboratory, Tuscaloosa, Alabama.

    Online Links:

    Other_Citation_Details:
    Alabama Maps is an ongoing project of the Cartographic Research Laboratory, which operates under the auspices of the College of Arts and Sciences at the University of Alabama. The Cartographic Research Laboratory , established in 1982, is a self-supporting, nonprofit facility, receiving funding through the sale of our publications and projects from clientele. The Aerial Photography Index contains a digitized selection of historic aerial photography found at the Geological Survey of Alabama and the University of Alabama Map Library. The photos found in this index are but a small part of the total collection of nearly 150,000 photographs housed in these facilities.
    Type_of_Source_Media: Digital and/or Hardcopy Resources
    Source_Scale_Denominator: 40000
    Source_Contribution:
    Imagery provided by the Cartographic Research Laboratory as high-resolution scans (.tif) via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
    Dauphin_1985 (source 5 of 10)
    U.S. Geological Survey (USGS), 19980804, National High Altitude Photography, Mobile County, Alabama, 1985: U.S. Geological Survey (USGS) ) Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota.

    Online Links:

    Other_Citation_Details:
    The National High Altitude Photography (NHAP) program, which was operated from 1980-1989, was coordinated by the U.S. Geological Survey as an interagency project to eliminate duplicate photography in various government programs. The aim of the program was to cover the 48 conterminous states over a 5-year span. In the NHAP program, black-and-white and color-infrared aerial photographs were obtained on 9-inch film from an altitude of 40,000 feet above mean terrain elevation and are centered over USGS 7.5-minute quadrangles. The color-infrared photographs are at a scale of 1:58,000 (1 inch equals about .9 miles), and the black-and-white photographs are at a scale of 1:80,000 (1 inch equals about 1.26 miles). All NHAP flights were flown in a North to South direction. These photographs are offered as digital images.
    Type_of_Source_Media: Digital and/or Hardcopy Resources
    Source_Scale_Denominator: 58000
    Source_Contribution:
    Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
    Dauphin_1989 (source 6 of 10)
    U.S. Geological Survey (USGS), 19900125, Aerial Single Frame Photos - Dauphin Island 1989: U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota.

    Online Links:

    Other_Citation_Details:
    The Aerial Photography Single Frame Records collection is a large and diverse group of imagery acquired by Federal organizations from 1937 to the present. Over 6.4 million frames of photographic images are available for download as medium and high resolution digital products. The high resolution data provide access to photogrammetric quality scans of aerial photographs with sufficient resolution to reveal landscape detail and to facilitate the interpretability of landscape features. Coverage is predominantly over the United States and includes portions of Central America and Puerto Rico. Individual photographs vary in scale, size, film type, quality, and coverage.
    Type_of_Source_Media: Digital and/or Hardcopy Resources.
    Source_Scale_Denominator: 65000
    Source_Contribution:
    Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
    Dauphin_1992 (source 7 of 10)
    U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center, 19970514, Digital Orthophoto Quadrangle, Dauphin Island, Alabama, 1992: U.S. Geological Survey, Menlo Park, CA USA.

    Online Links:

    Other_Citation_Details:
    Orthophotos combine the image characteristics of a photograph with the geometric qualities of a map. The primary digital orthophotoquadrangle (DOQ) is a 1-meter ground resolution, quarter-quadrangle (3.75 minutes of latitude by 3.75 minutes of longitude) image cast on the Universal Transverse Mercator projection (UTM) on the North American Datum of 1983 (NAD83). The geographic extent of the DOQ is equivalent to a quarter-quadrangle plus the overage ranges from a minimum of 50 meters to a maximum of 300 meters beyond the extremes of the primary and secondary corner points. The overage is included to facilitate tonal matching for mosaicking and for the placement of the NAD83 and secondary datum corner ticks. The normal orientation of data is by lines (rows) and samples (columns). Each line contains a series of pixels ordered from west to east with the order of the lines from north to south. The radiometric image brightness values are stored as 256 gray levels, ranging from 0 to 255. The standard, uncompressed gray scale DOQ format contains an ASCII header followed by a series of 8-bit image data lines. The keyword-based, ASCII header may vary in the number of data entries. The header is affixed to the beginning of the image and is composed of strings of 80 characters with an asterisk (*) as character 79 and an invisible newline character as character 80. Each keyword string contains information for either identification, display, or registration of the image. Additional strings of blanks are added to the header so that the length of a header line equals the number of bytes in a line of image data. The header line will be equal in length to the length of an image line. If the sum of the byte count of the header is less than the sample count of one DOQ image line, then the remainder of the header is padded with the requisite number of 80-character blank entries, each terminated with an asterisk and newline character.
    Type_of_Source_Media: Digital and/or Hardcopy Resources
    Source_Scale_Denominator: 40000
    Source_Contribution:
    Imagery provided by EROS via direct download. Imagery was used to delineate and digitize shoreline positions.
    Dauphin_1997 (source 8 of 10)
    U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center, 19970211, The National Aerial Photography Program Imagery, Mobile County, Alabama, 1997: U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota.

    Online Links:

    Other_Citation_Details:
    The National Aerial Photography Program (NAPP) was coordinated by the USGS as an interagency project to acquire cloud-free aerial photographs at an altitude of 20,000 feet above mean terrain elevation. The photographs were taken with a 6-inch focal length lens and are at a scale of 1:40,000. Coverage over the conterminous United States includes both black-and-white (BW) and color infrared (CIR) aerial photographs. Film type and extent of coverage were determined by available funds and operational requirements. The NAPP program, which was operational from 1987 to 2007, consists of more than 1.3 million images. Photographs were acquired on 9-inch film and were centered over quarters of USGS 7.5-minute quadrangles.Photographs are available as medium resolution digital images in Tagged Image File Format (TIFF). Medium resolution digital products were created with a digital single-lens reflex camera at a resolution of 63 microns, or 400 dots per inch (dpi).
    Type_of_Source_Media: Digital and/or Hardcopy Resources.
    Source_Scale_Denominator: 40000
    Source_Contribution:
    Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
    Dauphin_2006 (source 9 of 10)
    USDA-FSA-APFO, 20061206, USDA-FSA-APFO Digital Ortho Mosaic, Mobile County, Alabama, 2006: USDA_FSA_APFO Aerial Photography Field Office, Salt Lake City, Utah.

    Online Links:

    Other_Citation_Details:
    This data set contains imagery from the National Agriculture Imagery Program (NAIP). NAIP acquires digital ortho imagery during the agricultural growing seasons in the continental U.S.. A primary goal of the NAIP program is to enable availability of ortho imagery withone year of acquisition. NAIP provides four main products: 1-meter ground sample distance (GSD) ortho imagery rectified to a horizontal accuracy of within +/- 5meters of reference digital ortho quarter quads (DOQQ's) from the National Digital Ortho Program (NDOP); 2-meter GSD ortho imagery rectified to within +/- 10 meters of reference DOQQs; 1-meter GSD ortho imagery rectified to within +/- 6 meters to true ground; and, 2 meter GSD ortho imagery rectified to within +/- 10 meters to true ground. The tiling format of NAIP imagery is based on a 3.75' x 3.75' quarter quadrangle with a 300-meter buffer on all four sides. NAIP quarter quads are formatted to the UTM coordinate system using NAD83. NAIP imagery may contain as much as 10% cloud cover per tile. Dauphin_2006 was generated by compressing NAIP quarter quadrangle tiles that cover a county. MrSID compression, with mosaic option, was used. Target values for the compression ratio are (15:1) and maximum number of compression levels are used.
    Type_of_Source_Media: Digital and/or Hardcopy Resources.
    Source_Scale_Denominator: 40000
    Source_Contribution:
    Imagery provided by USDA Geospatial Data Gateway via direct download. Imagery was used to delineate and digitize shoreline positions.
    Dauphin_2015 (source 10 of 10)
    USDA-FSA-APFO, 20151112, USDA-FSA-APFO Digital Ortho Mosaic, Mobile County, Alabama, 2015: USDA_FSA_APFO Aerial Photography Field Office, Salt Lake City, Utah.

    Online Links:

    Type_of_Source_Media: Digital and/or Hardcopy Resources.
    Source_Scale_Denominator: 12000
    Source_Contribution:
    Imagery provided by USDA Geospatial Data Gateway via direct download. Imagery was used to delineate and digitize shoreline positions.
  2. How were the data generated, processed, and modified?
    Date: 16-May-2016 (process 1 of 2)
    Imagery was acquired from multiple agencies as direct download or as hard copy. The images are projected to Universal Transverse Mercator (UTM), Zone 16, North American Datum (NAD) 1983, meters (m) coordinates. If the imagery was not georeferenced when obtained, the corner coordinates and multiple control points were used to georeference the image using the ArcMap 10.3.1 "Georeference" toolbar. Using the ArcMap editor toolbar, shorelines were digitized based on aerial imagery.
    Shorelines were digitized based on a visual assessment of the WDL along sandy beaches and the approximation of mean high water where vegetation indicated. Shorelines were digitized at a scale of 1:1000. Once digitization was complete, shoreline segments were given attributes “DATE_” (text string 10 characters) and "UNCERT" (double), and "NOTES_". "DATE_" is determined from the aerial imagery collection date in MM/DD/YYYY format, "UNCERT" remains blank until completion of shoreline positional uncertainty (to follow). "NOTES_" contain information about each shoreline segment, according to 1) location along the island (for example, Dauphin Island, Little Dauphin Island, Pelican Island) and shoreline type (open-ocean, back-barrier, marsh shoreline).
    Once all data was populated with dates, the shoreline years were combined into one shapefile. Person who carried out this activity:
    Paul R Nelson
    U.S. Geological Survey
    600 4th Street South
    St. Petersburg, Florida
    US

    (727)-502-8127 (voice)
    prnelson@usgs.gov
    Data sources used in this process:
    • Dauphin_1940
    • Dauphin_1952
    • Dauphin_1960
    • Dauphin_1974
    • Dauphin_1985
    • Dauphin_1989
    • Dauphin_1992
    • Dauphin_1997
    • Dauphin_2006
    • Dauphin_2015
    Data sources produced in this process:
    • Aerial_WDL_Shorelines_1940_2015
    Date: 01-Mar-2017 (process 2 of 2)
    In order to determine the uncertainties associated with individual shorelines, a methodology following Morton and Miller (2005) and Hapke and others, (2006) was used to estimate a positional uncertainty value for each shoreline. Total shoreline positional uncertainty is a function of the errors inherent in the source data (georeferencing RMS) the interpretation of the shoreline feature (WDL positional variability) and those errors generated in the digitization of the vector shoreline (interpolation uncertainty/cell size).
    Three terms were identified to describe the shoreline positional uncertainty of the WDL shoreline. The first is the total image RSS of the georeferenced aerial imagery. This measure takes into account the accuracy of the georeferenced image, as well as the uncertainty of the base to which the imagery was georeferenced to. The second term is based on the natural variability of the shoreline proxy. The positional variability of an interpolated WDL shoreline is influenced primarily by tides, winds, waves and beach slope. Similarly, other water level based proxies (HWL - high water line, LHTS- last high tide swash) have positional variability which is weather and tide dependent. Drawing on methods presented in Pajak and Leathermann (2002), a conservative estimate of WDL variability (given tide range and average beach slope) of 4.5 m is calculated for Dauphin Island. The third and final term is based on the cell size of the georeferenced image, which relates to the scale of the image and accounts for limitations of shoreline interpretation from the raster data.
    These terms were summed in quadrature and the resulting shoreline positional uncertainty was applied to each shoreline date in the "UNCERT" field of the attribute table. This value is used to determine the uncertainty of shoreline change rates when used with the Digital Shoreline Analysis System (DSAS; Thieler and others, 2009). Person who carried out this activity:
    Rachel Henderson
    U.S. Geological Survey
    600 4th Street South
    St. Petersburg, Florida
    US

    (727)-502-8000 (voice)
    rehenderson@usgs.gov
    Data sources used in this process:
    • Aerial_WDL_Shorelines_1940_2015
    Data sources produced in this process:
    • Aerial_Shorelines_1940_2015.shp
  3. What similar or related data should the user be aware of?
    Pajak, M. J., and Leatherman, S., 2002, The High Water Line as Shoreline Indicator: Journal Vol. 18, No. 2, Journal of Coastal Research, Coastal Education & Research Foundation, Inc..

    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 - St. Petersburg Coastal and Marine Science Center, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Although the citation is for v. 4.0, the version of software at time of use was 4.3
    Hapke, C.J., Reid, D., Richmond, B.M., Ruggiero, P., and List, J., 2006, National Assessment of Shoreline Change: Part 3: Historical Shoreline Changes and Associated Coastal Land Loss along the Sandy Shorelines of the California Coast: Open-File Report 2006-1219, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal & Marine Science Center, Woods Hole, MA.

    Online Links:

    Hapke, Cheryl J., Himmelstoss, Emily A., Kratzmann, Meredith G., List, Jeffrey, and Thieler, E. Robert, 20110223, 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, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Morton, R. A., and Miller, T.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, Coastal and Marine Geology Program, Woods Hole Coastal & Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details: none

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

  1. How well have the observations been checked?
    The data provided here are a compilation of shorelines from aerial imagery from 1940 to 2015. The attributes are based on the requirements of the Digital Shoreline Analysis System (DSAS) software and have gone through a series of quality assurance procedures.
  2. How accurate are the geographic locations?
    In order to determine the uncertainties associated with individual shorelines, a methodology following Morton and Miller (2005) and Hapke and others, (2006) was used to estimate a positional uncertainty value for each shoreline. Total shoreline positional uncertainty is a function of the errors inherent in the source data (georeferencing Root Mean Square [RMS]) the interpretation of the shoreline feature (WDL positional variability) and those errors generated in the digitization of the vector shoreline (interpolation uncertainty/cell size).
    Three terms were identified to describe the shoreline positional uncertainty of the WDL shoreline. The first is the total image Root Sum Squared (RSS) of the georeferenced aerial imagery. This measure takes into account the accuracy of the georeferenced image, as well as the uncertainty of the base to wich the imagery was georeferenced to. The second term is based on the natural variability of the shoreline proxy. The positional variability of an interpolated WDL shoreline is influenced primarily by tides, winds, waves and beach slope. Similarly, other water level based proxies (HWL - high water line, LHTS- last high tide swash) have positional variability, which is weather and tide dependent. Drawing on methods presented in Pajak and Leathermann (2002), a conservative estimate of WDL variability (given tide range and average beach slope) of 4.5 m is calculated for Dauphin Island. The third and final term is based on the cell size of the georeferenced image, which relates to the scale of the image and accounts for limitations of shoreline interpretation from the raster data.
    These terms were summed in quadrature and the resulting shoreline positional uncertainty was applied to each shoreline date in the "UNCERT" field of the attribute table. This value is used to determine the uncertainty of shoreline change rates when used with the Digital Shoreline Analysis System (DSAS; Thieler and others, 2009).
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    Digitized shorelines were checked to ensure they were one continuous line and were checked for dangles (or extra line segments), which were removed, when necessary. Larger estuarine channels were digitized, as needed, to ensure a complete shoreline for later use within shoreline change programs.

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:
The U.S. Geological Survey requests to be acknowledged as originator of the data in future products or derivative research. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey Coastal and Marine Science Center
    Attn: Paul R. Nelson
    600 4th Street South
    St. Petersburg, FL

    727-502-8127 (voice)
    727-502-8182 (FAX)
    prnelson@usgs.gov
  2. What's the catalog number I need to order this data set? Aerial_Shorelines_1940_2015.
  3. What legal disclaimers am I supposed to read?
    This digital publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 23-Jun-2017
Metadata author:
U.S. Geological Survey Coastal and Marine Science Center
Attn: Paul R. Nelson
600 4th Street South
St. Petersburg, FL

727-502-8127 (voice)
727-502-8182 (FAX)
prnelson@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/Aerial_Shorelines_metadata.faq.html>
Generated by mp version 2.9.49 on Mon Sep 10 17:44:17 2018