Land-Cover Data Derived from Landsat Satellite Imagery, Assateague Island to Metompkin Island, Maryland and Virginia, 1985 and 2015

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Frequently anticipated questions:


What does this data set describe?

Title:
Land-Cover Data Derived from Landsat Satellite Imagery, Assateague Island to Metompkin Island, Maryland and Virginia, 1985 and 2015
Abstract:
This U.S. Geological Survey (USGS) data release includes geospatial datasets that were created to analyze wetland changes along the Virginia and Maryland Atlantic coasts between 1984 and 2015. 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). USGS Data Series 968 (Bernier and others, 2015) presented data that were derived from Landsat 5 and Landsat 8 imagery from 1984 to 2014, including wetland and terrestrial habitat extents; open-ocean, back-barrier, and estuarine mainland shoreline positions; and sand-line positions along the estuarine mainland and barrier shorelines from Assateague Island, Maryland to Metompkin Island, Virginia. As part of the wetland-change analyses, two additional satellite images (17-April-1985 and 05-May-2015) were processed and classified using the methods described by Bernier and others (2015) to provide a more complete time series dataset. One additional image (26-April-1994) was reprocessed to correct a classification error that was identified when comparing wetland and total analysis extents among all images.
Supplemental_Information:
This data release includes three raster GeoTIFF files. The two newly classified images are T19850417_lt5_a2a_lc_final.tif and T20150522_lc8_a2a_lc_final.tif. The reprocessed, classified image is named T19940426_lt5_a2a_lc_final_rev12_2016.tif. The geographic information system data presented by Bernier and others (2015), along with accompanying formal Federal Geographic Data Committee (FGDC) metadata, can be downloaded from https://pubs.usgs.gov/ds/0968/ds968_data.html.
  1. How might this data set be cited?
    Bernier, Julie C., 20170828, Land-Cover Data Derived from Landsat Satellite Imagery, Assateague Island to Metompkin Island, Maryland and Virginia, 1985 and 2015: 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
    Currentness_Reference:
    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 2169 x 1739 x 1, type Grid Cell
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 18
      Transverse_Mercator:
      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?
    T19850417_lt5_a2a_final.tif, T19940426_lt5_a2a_lc_final_rev12_2016.tif, T20150522_lc8_a2a_lc_final.tif
    GeoTIFF files containing thematic raster datasets representing land-cover classes for each of two Landsat 5 and one Landsat 8 image aquired in 1985 and 2015. (Source: USGS)
    OBJECTID
    Internal feature number (Source: Esri) Sequential unique whole numbers that are automatically generated
    Value
    Land-cover class number (Source: USGS)
    ValueDefinition
    0OUT - pixels outside of analysis extent
    1WATER - pixels classified as water
    4WET MARSH - pixels classified as wet marsh land cover
    6MARSH - pixels classified as marsh land cover
    7FORESTED - pixels classified as forested land cover
    9MIXED VEGETATION - pixels classified as mixed vegetation land cover
    10VEGETATED BARE EARTH - pixels classified as vegetated bare earth land cover
    11BARE EARTH - pixels classified as bare earth
    Count
    The number of cells per value class. (Source: USGS)
    Range of values
    Minimum:3123
    Maximum:2615233
    Units:Dimensionless

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Julie C. Bernier
  2. Who also contributed to the data set?
    U.S. Geological Survey, Coastal and Marine Geology Program, St. Petersburg Coastal and Marine Science Center
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Julie Bernier
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    jbernier@usgs.gov

Why was the data set created?

This zip archive includes thematic raster data representing land-cover classes derived from two Landsat 5 Thematic Mapper (TM) and one Landsat 8 Operational Land Imager (OLI) image datasets from Assateague Island to Metompkin Island, Maryland and Virginia. For each image acquisition date, the Level 1 data products were stacked into composite 6-band (visible blue, green, and red; near infrared; and two short-wave infrared bands) image files and converted to at-sensor radiance and top-of-atmosphere reflectance. Adjacent scenes (Worldwide Reference System 2, path 14 row 33 and path 14 row 34) were mosaicked to a single image and then clipped to the study area extent. Seven land-cover classes (water, wet marsh, marsh, forested, mixed vegetation, vegetated bare earth, and bare earth) were derived for each image acquisition date using a hybrid classification approach to minimize misclassification of small interior water bodies and tidal channels with surrounding marsh environments.

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: 2016 (process 1 of 4)
    Each Landsat Level 1 data product was stacked into a composite multi-band image file using Intergraph Corporation ERDAS IMAGINE 2014 software. The six reflective bands (visible blue, green, and red; near infrared; and two short-wave infrared bands) for each sensor were stacked and used in subsequent processing and analyses. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Julie Bernier
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    jbernier@usgs.gov
    Date: 2016 (process 2 of 4)
    The composite multi-band image files were converted to at-sensor radiance and top-of-atmosphere (TOA) reflectance using Intergraph Corporation ERDAS IMAGINE 2014 software. Radiometric processing reduces scene-to-scene variability, due to gain changes between scenes or differences in solar zenith angles, exoatmospheric solar irradiance, and the earth-sun distance resulting from different acquisition dates and times. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Julie Bernier
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    jbernier@usgs.gov
    Date: 2016 (process 3 of 4)
    For each image acquisition date, adjacent scenes (Worldwide Reference System 2, path 14 row 33 and path 14 row 34) were mosaicked into a single image and clipped to the study area extent. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Julie Bernier
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    jbernier@usgs.gov
    Date: 2016 (process 4 of 4)
    Image classification was performed using Intergraph Corporation ERDAS IMAGINE 2014 software. A hybrid classification approach was used to minimize misclassification of small interior water bodies and tidal channels with surrounding marsh environments: (1) A 3×3 (pixel) edge enhancement convolution filter was applied to the radiometrically corrected, mosaicked images to enhance small water features; (2) Unsupervised classification was performed on the edge-enhanced image to identify and extract water areas; (3) Water areas from (2) were masked from the non edge-enhanced image and unsupervised classification of the remaining pixels was grouped into seven classes (water, wet marsh, marsh, forested, mixed vegetation, vegetated bare earth, and bare earth); and (4) Results of (2) and (3) were merged to generate a final thematically classified raster dataset. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Julie Bernier
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    jbernier@usgs.gov
  3. What similar or related data should the user be aware of?
    Bernier, J.C., Douglas, S.D., 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?
  2. How accurate are the geographic locations?
    Geodetic accuracy of the Standard Terrain Correction (Level 1T) data product 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?
  4. Where are the gaps in the data? What is missing?
    Two Landsat 5 Thematic Mapper (TM) and one Landsat 8 Operational Land Imager (OLI) image were analyzed.
  5. How consistent are the relationships among the observations, including topology?
    Landsat standard data products, processed using the Level 1 Product Generation System (LPGS), were downloaded from the USGS Earth Resources Observation and Science (EROS) Center data archives. Even after using a hybrid classification approach, some areas that were classified as wet marsh in the final thematic raster dataset appeared, upon visual inspection, to include submerged aquatic vegetation and submerged sand flats that would be more appropriately classified as open water. These ambiguities are not consistent through time but most commonly occur in Sinepuxent Bay south of Ocean City Inlet, north of Green Run Bay and Pirate Islands, in impoundments behind Chincoteague Island, and at Chincoteague Inlet. Similarly, in some instances, areas that were classified as water in the final thematic raster dataset were interpreted as wet sand on visual inspection. This most commonly occurs along the narrowest part of Assateague Island south of Ocean City Inlet, at the Tom’s Cove spit, and along Metompkin Island. Additionally, some near-shore estuarine areas exhibit “speckling” caused by misclassification of isolated higher reflectance pixels within the water body. No manual cleaning of open-water speckling or potentially misclassified pixels was performed.

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 that it be acknowledged as the originator of this dataset in any future products or research derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey
    Attn: Julie Bernier
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    jbernier@usgs.gov
  2. What's the catalog number I need to order this data set?
  3. What legal disclaimers am I supposed to read?
    This 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, or for general or scientific purposes, 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?
  5. What hardware or software do I need in order to use the data set?
    These raster datasets were created using Esri ArcGIS version 10.2.2 and can be opened using Esri ArcGIS version 10.0 or higher; these data may also be viewed using the free GIS viewer ArcGIS Explorer.

Who wrote the metadata?

Dates:
Last modified: 23-May-2018
Metadata author:
U.S. Geological Survey
Attn: Julie Bernier
Geologist
600 4th Street South
St. Petersburg, FL
USA

727-502-8000 (voice)
jbernier@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/landsat_a2a_lc_final_v2016-met.faq.html>
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