Shorelines Extracted from 1984-2015 Landsat Imagery: Cat Island, Mississippi (Polygon: Combined Dates)

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Frequently anticipated questions:


What does this data set describe?

Title:
Shorelines Extracted from 1984-2015 Landsat Imagery: Cat Island, Mississippi (Polygon: Combined Dates)
Abstract:
Shorelines Extracted from 1984-2015 Landsat Imagery: Cat Island, Mississippi (Polygon: Combined Dates) is a polygon shapefile representing shorelines generated from satellite imagery that was collected from 1984 to 2015. The sample frequency of satellite imagery is much higher, and the coverage much greater, than most routine high-resolution topographic surveys. Certain aspects of barrier island morphology, such as island size, shape and position, can be determined from these images and can indicate erosion, land loss, and island breakup. Studying how these characteristics evolve will help develop an understanding of how barrier islands will respond to climate change, sea level rise, and major storms in the future and that will serve to improve management of coastal resources.
  1. How might this data set be cited?
    U.S. Geological Survey, 2015, Shorelines Extracted from 1984-2015 Landsat Imagery: Cat Island, Mississippi (Polygon: Combined Dates): U.S. Geological Survey Data Release doi:10.5066/F7JQ0Z3R, U.S. Geological Survey, St. Petersburg, Florida..

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -89.161974
    East_Bounding_Coordinate: -89.059516
    North_Bounding_Coordinate: 30.255079
    South_Bounding_Coordinate: 30.200014
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 25-Mar-1984
    Ending_Date: 23-May-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):
      • G-polygon (19170)
    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 Geographic Coordinate System World Geodetic System WGS 1984.
      The ellipsoid used is World Geodetic System 1984.
      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?
    cat_po_19840325_20150523.shp
    Esri polygon features representing Cat Island, Mississippi shorelines from 1984-2015. The SPCMSC created 268 individual date shapefiles that were subsequently combined into one shapefile. (Source: USGS)
    FID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri)
    ValueDefinition
    PolygonShape of feature.
    Date_
    Date of satellite image source. (Source: USGS) Date that the source image was collected in month, day, and year format.
    Area_
    ???. (Source: USGS or Esri?)
    Range of values
    Minimum:2.90950381
    Maximum:14342896.8
    YYYYMMDD
    Date that the source image was collected formatted as an 8-digit number representing the year, month, and day. (Source: USGS) Date formatted as an 8-digit number representing year, month, and day.
    WXT32Dau
    The predicted tide level, in meters relative to MLLW, at the Dauphin Island tide station at the time of image collection. These data were obtained from WXTide32 (www.wxtide32.com), a tide and current prediction program. (Source: USGS)
    Range of values
    Minimum:-0.26
    Maximum:0.80
    Landsat
    The Landsat satellite number. (Source: USGS)
    ValueDefinition
    5Number of the Landsat satellite.
    7Number of the Landsat satellite.
    8Number of the Landsat satellite.

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?
    Acknowledgment of the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center Coastal and Marine Geology Program (SPCMSC), 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
    Attn: Kristy Guy
    600 4th St. S.
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    727-502-8181 (FAX)
    kguy@usgs.gov
    Hours_of_Service: Monday through Friday 9:00 AM to 5:00 PM (Eastern Time)

Why was the data set created?

To document the Cat Island, Miss. shorelines, from March 25, 1984 to May 23, 2015 as observed from Landsat 5 Thematic Mapper (TM), Landsat 7 Enhanced Thematic Mapper Plus (ETM+), and Landsat Operational Land Imager (OLI) satellite imagery. These data will aid in developing an understanding of the change in barrier island size, shape and position, which can indicate erosion, land loss and island breakup. This dataset, cat_polys_combined_dates.zip, and others are included in a USGS Data Release, which can be accessed online at http://dx.doi.org/10.5066/F7JQ0Z3R.

How was the data set created?

  1. From what previous works were the data drawn?
    Landsat 5 TM (source 1 of 3)
    USGS, 2011, USGS Landsat 5 TM Images: USGS Earth Resources Observation and Science (EROS) Center, Sioux Falls, SD.

    Type_of_Source_Media: online
    Source_Contribution:
    This data source was used to identify barrier island shorelines.
    Landsat 7 ETM+ (source 2 of 3)
    USGS, 2003, USGS Landsat 7 ETM+ Images: USGS Earth Resources Observation and Science (EROS) Center, Sioux Falls, SD.

    Type_of_Source_Media: online
    Source_Contribution:
    This data source was used to identify barrier island shorelines.
    Landsat 8 OLI (source 3 of 3)
    USGS, 2015, USGS Landsat 8 OLI Images: USGS Earth Resources Observation and Science (EROS) Center, Sioux Falls, SD.

    Type_of_Source_Media: online
    Source_Contribution:
    This data source was used to identify barrier island shorelines.
  2. How were the data generated, processed, and modified?
    Date: 2015 (process 1 of 2)
    Landsat 5 Thematic Mapper (TM), Landsat 7 Enhanced Thematic Mapper Plus (ETM+), and Landsat 8 Operational Land Imager (OLI) satellite imagery were acquired in digital format from the U.S. Geological Survey Global Visualization Viewer (http://glovis.usgs.gov/). Images were selected based on cloud-free areas of interest. Landsat 7 ETM+ images after May 2003 were not used due to striping caused by the failure of the instrument's scan-line corrector. The Landsat images were processed using ArcGIS. Images were subset (trimmed) to the area of interest and isolines were generated based on the numerical values of band 7. Band 7, an infrared band (2.08-2.35 µm for TM, 2.09-2.35 µm for ETM+, 2.11-2.29 µm for OLI), clearly distinguishes land from water due to the absorption of these wavelengths by water (Lillesand and Kiefer, 1987) resulting in a low reflectance in contrast to the higher reflectance of land areas, particularly sand. Each isoline was visually compared with its corresponding image and the isoline that best represented the land/water line was selected to represent the shoreline and saved to a shapefile. When necessary, small hand edits were made to the selected isolines. The line features were then converted to polygons. The individual date polygon shapefiles were combined into one combined date shapefile. Wet, marshy shorelines were less reliably delineated using this method and varied more with tide level than the sandy shorelines. Predicted tide levels relative to Mean Lower Low Water (MLLW) from the Dauphin Island, Ala. tide station were obtained from a tide and current prediction program, WXTide32, (www.wxtide32.com) and added as an attribute to cat_po_19840325_20150523.shp. No adjustments were made to the shorelines for varying tide levels. Person who carried out this activity:
    USGS
    600 4th St. S.
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    727-502-8181 (FAX)
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Contact_Instructions:
    If unable to reach the contact by telephone, please leave a voice message.
    Data sources used in this process:
    • Landsat 5 TM
    • Landsat 7 ETM+
    • Landsat 8 OLI
    Data sources produced in this process:
    • cat_po_19840325_20150523.shp; cat_po_*.shp
    Date: 14-Feb-2017 (process 2 of 2)
    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?

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

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
    The horizontal accuracy of the data is unknown.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This dataset is considered complete for the information presented, as described in the abstract section. Users are advised to read the rest of the metadata record carefully for additional details. Landsat 7 ETM+ images after May 2003 were not used due to striping caused by the failure of the instrument's scan-line corrector. No shorelines were created for 2012 due to poor Landsat 7 image quality.
  5. How consistent are the relationships among the observations, including topology?
    Variations in image quality and in atmospheric and surface conditions may have affected the quality of the shorelines. Tide levels vary from image to image which affects the apparent shoreline. No adjustments were made for varying tide levels.

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:
None. However, variability in image quality from one date to another, from one image to another on the same date, and from one part of a single image to another part of the same image, exists due to many factors including variation in sun angle, atmospheric conditions, season, reflectivity of the earth surface, camera angle, camera lens, camera settings, film sensitivity, water turbidity, water depth, tide level, waves, and error in image rectification. No adjustments were made to account for tide level.
  1. Who distributes the data set? (Distributor 1 of 1)
    Kristy Guy
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, Fla.
    GIS/RS Analyst
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    Hours_of_Service: Monday-Friday, 9:00-5:00 Eastern Time
  2. What's the catalog number I need to order this data set? Downloadable data - USGS Data Release
  3. What legal disclaimers am I supposed to read?
    Although these data were processed successfully on a computer system at the USGS, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The USGS shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, firm, or product 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?

Who wrote the metadata?

Dates:
Last modified: 03-Aug-2017
Metadata author:
USGS
Attn: Kristy Guy
600 4th Street South
St. Petersburg, FL
USA

727-502-8000 (voice)
727-502-8181 (FAX)
kguy@usgs.gov
Hours_of_Service: Monday through Friday 9:00 AM to 5:00 PM (Eastern Time)
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/metadata_cat_landsat_shoreline_polys_combined_dates_19840325_20150523.faq.html>
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