Wetland-Change Data Derived from Landsat Imagery, Assateague Island to Metompkin Island, Maryland and Virginia, 1984 to 2015: Land-cover Change Analysis

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Frequently anticipated questions:

What does this data set describe?

Wetland-Change Data Derived from Landsat Imagery, Assateague Island to Metompkin Island, Maryland and Virginia, 1984 to 2015: Land-cover Change Analysis
This U.S. Geological Survey (USGS) data release includes geospatial datasets that were created for the analysis of Virginia and Maryland Atlantic coastal wetland changes over time. Wetland change was determined by assessing two metrics: wetland persistence and land-cover switching. Because seasonal water levels, beach width, and vegetation differences can affect change analyses, only images acquired during the spring (March, April, and May) were included in the wetland-change metrics (N=10). Land-cover switching was evaluated using Landsat images for successive spring image-acquisition dates: 1985–1989, 1989–1994, 1994–1999, 1999–2004, 2004-2009, 2009-2011, 2011-2013, 2013-2014, and 2014-2015. To evaluate land-cover switching, land-cover types defined by Bernier and others (2015) were reclassified as 1 (water), 3 (wetland), or 7 (non-wetland). These values were chosen so the results of subtracting two dates will create unique values for each scenario. For example, if a cell in 1994 is classified as land and in 1989 was wetland, the result (1994-1989 or 7-3) is 4. If the cell in 1994 is wetland and in 1989 was water (3-1) the result is 2. With this analysis, each two-date combination results in a raster that identifies wetland-land-water conversions, such that water-to-land is -6, wetland-to-land is -4, water-to-wetland is -2, wetland-to-water equals 2, land-to-wetland is 4, and land-to-water is 6.
The classification methodology and land-cover class definitions are described in Bernier and others (2015). Classified images for 1985-2014 are available in Bernier and other (2015) and classified images for 1984 and 2015 are available in this data release. Downloadable versions of the final data are provided in GeoTIFF file format with 30-meter (m) resolution.
  1. How might this data set be cited?
    Douglas, Steven H., Bernier, Julie C., and Smith, Kathryn E.L., 20170828, Wetland-Change Data Derived from Landsat Imagery, Assateague Island to Metompkin Island, Maryland and Virginia, 1984 to 2015: Land-cover Change Analysis: U.S. Geological Survey Data Release doi:10.5066/F76T0KHH, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -75.589992
    East_Bounding_Coordinate: -74.993823
    North_Bounding_Coordinate: 38.327077
    South_Bounding_Coordinate: 37.739698
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 17-Apr-1985
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: raster digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 2167 x 1737, type Grid Cell
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 18
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -75.0
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 30.0
      Ordinates (y-coordinates) are specified to the nearest 30.0
      Planar coordinates are specified in Meters
      The horizontal datum used is D WGS 1984.
      The ellipsoid used is WGS 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?
    04_09_wwl.tif, 09_11_wwl.tif, 11_13_wwl.tif, 13_14_wwl.tif, 14_15_wwl.tif, 85_89_wwl.tif, 89_94_wwl.tif, 94_99_wwl.tif, 99_04_wwl.tif
    GeoTIFF files containing the results of land-cover change analyses (also referred to as land-cover switching). Each table associated with the raster image includes attribute information for each dataset. (Source: USGS)
    Internal feature number. Sequential, unique whole numbers that are automatically generated. (Source: Esri)
    Range of values
    Land cover change type by time step. (Source: USGS)
    The number of cells per value class. (Source: USGS)
    Range of values

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Steven H. Douglas
    • Julie C. Bernier
    • Kathryn E.L. Smith
  2. Who also contributed to the data set?
    U.S. Geological Survey
  3. To whom should users address questions about the data?
    Cherokee Nation Technologies contracted to the U.S. Geological Survey
    Attn: Steven H. Douglas
    600 4th St S
    St. Petersburg, FL

    727-502-8000 (voice)

Why was the data set created?

The purpose of this analysis was to evaluate the effect of coastal hazards, such as Hurricane Sandy, on the extent of coastal marshes.

How was the data set created?

  1. From what previous works were the data drawn?
    NOAA MHW (source 1 of 1)
    National Oceanographic and Atmospheric Administration (NOAA), 2016, Observed Water Levels: NOAA, Silver Springs, MD.

    Online Links:

    Type_of_Source_Media: digital
    Source information used in analysis of water level contribution to land cover change.
  2. How were the data generated, processed, and modified?
    Date: 2016 (process 1 of 3)
    Land cover types were reclassified into three classes 1 (water), 3 (wetland), and 7 (non-wetland) using the reclassify tool in ArcGIS. The water classification from Bernier and others (2015) and this data release was left as water. Wet marsh, marsh, and mixed vegetation were reclassified as wetland. Forested, vegetated bare earth, and bare earth were reclassified as non-wetland land cover classes. Reclassified rasters were subtracted from one another using the raster calculator tool. Person who carried out this activity:
    Steven H. Douglas
    Cherokee Nation Technologies contracted to the U.S. Geological Survey
    600 4th St S
    St Petersburg, FL

    727-502-8000 (voice)
    Date: 2016 (process 2 of 3)
    Daily Mean High Water (MHW) data (in meters) were exported from the NOAA tides and currents website as .csv files.
    Date: 13-Oct-2020 (process 3 of 3)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
  3. What similar or related data should the user be aware of?
    Bernier, J.C., Douglas, S.H., Terrano, J.F., Barras, J.A., Plant, N.G., and Smith, C.G., 2015, Land-cover types, shoreline positions, and sand extents derived from Landsat satellite imagery, Assateague Island to Metompkin Island, Maryland and Virginia, 1984 to 2014: U.S. Geological Survey Data Series 968.

    Online Links:

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

  1. How well have the observations been checked?
    Accuracy assessments were performed on six of the land-cover datasets for which reference aerial photography datasets from the same year were available to determine how well the classification process represents the land cover at the time of image acquisition. Using high-resolution aerial photographs from 1989, 2005, 2009, 2011, 2013, and 2015 as ancillary data, the land-cover class at each point was visually compared to assess if the pixel was classified correctly. The overall accuracy ranged from 86.6% (April 1989) to 92% (April 2011). Most errors of commission occurred when small tidal creeks that cannot be resolved using 30-m resolution Landsat imagery were misclassified with the surrounding wetlands. Water-level differences between Landsat image acquisition and aerial photography acquisition may also contribute to some errors of commission. The National Agriculture Imagery Program (NAIP) aerial photographs used to ground truth the land-cover classification were generally acquired during the summer months, rather than spring or fall, over periods ranging from days to months.
  2. How accurate are the geographic locations?
    Geodetic accuracy of the Standard Terrain Correction (Level 1T) source data product used to define the land-cover classes depends on the accuracy of the ground control points and the resolution of the Digital Elevation Model (DEM) used.
  3. How accurate are the heights or depths?
    A formal accuracy assessment of the vertical positional information in the data set has either not been conducted, or is not applicable.
  4. Where are the gaps in the data? What is missing?
    Data set is considered complete for the information presented, as described in the abstract.
  5. How consistent are the relationships among the observations, including topology?
    Raster values were checked for consistency with expected values.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
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)
    Cherokee Nation Technologies contracted to the U.S. Geological Survey
    Attn: Steven Douglas
    600 4th St S
    St Petersburg, FL

    727-502-8134 (voice)
  2. What's the catalog number I need to order this data set?
  3. What legal disclaimers am I supposed to read?
    Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The data have been approved for release and publication by the U.S. Geological Survey (USGS). Although the data have been subjected to rigorous review and are substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, the data are released on the condition that neither the USGS nor the U.S. Government may be held liable for any damages resulting from authorized or unauthorized use. Although the data have been 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. Users of the data are advised to read all metadata and associated documentation thoroughly to understand appropriate use and data limitations.
  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 13-Oct-2020
Metadata author:
Cherokee Nation Technologies contracted to the U.S. Geological Survey
Attn: Steven H. Douglas
600 4th St S
St. Petersburg, FL

727-502-8000 (voice)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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