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Potential Eelgrass Beds

Frequently-asked questions:


What does this data set describe?

Title:
Potential Eelgrass Beds

Abstract:
Potential Eelgrass Beds is a 1:24,000 scale, polygon feature-based layer that depicts the locations of potential eelgrass beds in Long Island Sound, in major rivers, and within bays, harbors and other waterbodies along Connecticut's coast.  The layer is based on information from the Observed Eelgrass Beds and Eelgrass Sample Points layers.  It represents conditions at a particular point in time (1993 to 1995).  During the 1993-95 field seasons a team of researchers from the University of Connecticut Dept. of Ecology and Evolutionary Biology led by Charles Yarish, equipped with a Global Positioning System (GPS), SCUBA, and a 20' boat surveyed over 800 potential eelgrass locations.  Their GPS coordinates and field notes were used to create a point coverage entitled Eelgrass Sample Points, which was plotted and checked on a 1:24000 scale base map of the Connecticut shore.  These point locations, observations, and the nearshore bathymetry were then used to delineate areas representing both observed and potential eelgrass beds.  Eelgrass beds were initially digitized at 1:24,000 scale, but have been edited and revised on screen at higher resolution.  Potential beds, where not individually delineated, were created by buffering observed beds a distance of 33 feet (10 meters).  These buffered polygons were intersected with buffered (distance of 5 ft.) shoreline arcs to keep potential polygons a minimum distance off the shoreline.  These potential beds are considered to be areas where eelgrass is likely to spread to under ideal conditions, where eelgrass may exist in small isolated patches, where eelgrass may exhibit high temporal variability, or perhaps where restoration projects could be undertaken.  

Feature locations may not always be exact due to equipment failure or lack of satellite reception.  In those cases, points were estimated from field notes.  It should be noted that the Potential Eelgrass Beds layer is not a complete dataset of all potential eelgrass sites in Connecticut and/or Long Island Sound.  This layer was published in 1997 and is not updated.  It does not represent current conditions.  

There are 67 polygon features representing potential eelgrass beds in this layer.  Geographic locations are as follows:  westernmost areas:  Clinton Harbor;  easternmost areas:  Little Narragansett Bay, Rhode Island waters.  Potential beds range in size from .179 acre (318 sq. ft.) to 471 acres (20,551,582 sq. ft.).  Potential beds contain 0 to 9 observed beds, and from 0 to 88.1% area covered by observed beds.  The total area of potential beds is 2,196 acres.

Supplemental information:
For more information, refer to the Eelgrass Sample Points and Observed Eelgrass Beds layers.

  1. How should this data set be cited?

    Dr. Charles Yarish, University of Connecticut Dept. of Ecology and Evolutionary Biology (compiler), Mary DiGiacomo-Cohen, Long Island Sound Resource Center (editor), State of Connecticut, Department of Environmental Protection (publisher), 1997, Potential Eelgrass Beds: State of Connecticut, Department of Environmental Protection, Hartford, Connecticut, USA.

    Online links:
    Other citation details:
    This layer is not updated and does not represent current conditions.

  2. What geographic area does the data set cover?

    Bounding coordinates:
    West: -72.546738
    East: -71.872643
    North: 41.368949
    South: 41.254288

  3. What does it look like?

    http://www.cteco.uconn.edu/metadata/dep/browsegraphic/eelgrassbedobpotfullview.gif (GIF)
    Full view of potential and observed eelgrass beds 1993-1995.

    http://www.cteco.uconn.edu/metadata/dep/browsegraphic/eelgrassbedobpotdetailview.gif (GIF)
    Detail view of potential and observed eelgrass beds 1993-1995.

  4. Does the data set describe conditions during a particular time period?

    Beginning date: 1993
    Ending date: 1995
    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?

      Indirect spatial reference:
      State of Connecticut, United States of America

      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • G-polygon (67)
      • Point (216)

    2. What coordinate system is used to represent geographic features?

      The map projection used is Lambert Conformal Conic.

      Projection parameters:
      Lambert Conformal Conic
      Standard parallel: 41.200000
      Standard parallel: 41.866667
      Longitude of central meridian: -72.750000
      Latitude of projection origin: 40.833333
      False easting: 999999.999996
      False northing: 499999.999998

      Planar coordinates are encoded using coordinate pair.
      Abscissae (x-coordinates) are specified to the nearest 0.000250.
      Ordinates (y-coordinates) are specified to the nearest 0.000250.
      Planar coordinates are specified in survey feet.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

      Vertical coordinate system definition:
      Altitude system definition:
      Altitude resolution: 1.000000
      Altitude encoding method: Explicit elevation coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    Potential Eelgrass Beds
    Potential Eelgrass Areas stored as digital vector data (Source: State of Connecticut, Department of Environmental Protection)

    OBJECTID
    Internal feature number. (Source: ESRI)
                      

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)
                      

    Coordinates defining the features.

    P_OBSERV
    Percent of area covered by observed eelgrass beds.   (Source: State of Connecticut, Department of Environmental Protection)
                      

    Percentages generated by mathematical calculation.

    FREQUENCY
    Number of point locations (Eelgrass Sample Points) within the polygon. (Source: State of Connecticut, Department of Environmental Protection)
                      

    Whole numbers.

    ACREAGE
    Area of feature in acres (SHAPE_AREA divided by 43560). (Source: State of Connecticut, Department of Environmental Protection)
                      

    Number generated by dividing Shape_Area by 43,560.

    SHAPE
    Feature geometry. (Source: ESRI)
                      

    Coordinates defining the features.

    POTENTIAL
    Existence of potential eelgrass areas. (Source: State of Connecticut, Department of Environmental Protection)
                      

    ValueDefinition
    Y
    Yes - potential eelgrass area exists.
    N
    No - Potential eelgrass area does not exist.

    SHAPE.area
    SHAPE.len
    Entity and attribute overview:
    Includes Potential Eelgrass Bed polygon features such as percent of area covered by observed eelgrass (P_OBSERV), existence of potential eelgrass areas (POTENTIAL), number of eelgrass sample point locations within the polygon (FREQUENCY), size of the feature in acres (ACREAGE), size of the feature in square feet (SHAPE_AREA), and perimiter of feature area (SHAPE_LENGTH).  
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Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)


  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    Kevin O'Brien
    State of Connecticut, Department of Environmental Protection
    79 Elm Street
    Hartford, Connecticut 06106-5127
    USA

    860-424-3034 (voice)
    860-424-4054 (FAX)
    dep.gisdata@ct.gov
    Hours of Service: Monday to Friday, 08:30 to 16:30 Eastern Standard Time
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Why was the data set created?

Potential Eelgrass Beds is 1:24,000-scale data.  The purpose of this datalayer is to depict the locations of potential eelgrass growth along Connecticut's coast.  The polygons in this layer were created from two source layers:  Eelgrass Sample Points and Observed Eelgrass Beds.  This layer is not intended for maps printed at map scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet.)

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How was the data set created?

  1. Where did the data come from?

    Source 1 - Eelgrass Sample Points Coverage (source 1 of 4)

    State of Connecticut, Department of Environmental Protection, University of Connecticut, Long Island Sound Resource Center, 1997, Eelgrass Sample Points .

    Online links:
    Type of source media: disc
    Source scale denominator: 24000
    Source contribution:
    This source served as the first of two major sources of base data for the creation of Potential Eelgrass Beds.  GPS coordinates and field notes were used to create the Eelgrass Sample Points coverage, which was plotted and checked on a 1:24000 scale base map of the Connecticut shore.  These point locations, observations, and the nearshore bathymetry were then used to delineate areas representing both observed and potential eelgrass beds.

    Source 2 - Observed Eelgrass Beds Coverage (source 2 of 4)

    State of Connecticut, Department of Environmental Protection, University of Connecticut, Long Island Sound Resource Center, 1997, Observed Eelgrass Beds.

    Online links:
    Type of source media: disc
    Source scale denominator: 24000
    Source contribution:
    This source served as the second of two major sources of base data for the creation of Potential Eelgrass Beds.  The Observed Eelgrass Beds layer was used to create potential eelgrass beds by buffering observed beds a distance of 33 feet (10 meters).  These buffered polygons were intersected with buffered (distance of 5 ft.) shoreline arcs to keep potential polygons a minimum distance off the shoreline.  

    Source 3 - Potential Eelgrass Beds Coverage (source 3 of 4)

    State of Connecticut, Department of Environmental Protection, University of Connecticut, Long Island Sound Resource Center, 1997, Potential Eelgrass Beds Coverage.

    Online links:
    Type of source media: disc
    Source scale denominator: 24000
    Source contribution:
    This data source refers to all features combined in one statewide layer. Since initial publication in 1997, subsequent publication of the layer was generated by the State of Connecticut in order to convert from NAD 27 to NAD 83. Consequently, a different copy of this layer was produced, representing the change in the state plane coordinate system.  Changes made to the entire layer are reflected in metadata process steps where this particular data source is cited as both the Source Used and the Source Produced.

    Source 4 - Potential Eelgrass Beds Shapefile (source 4 of 4)

    State of Connecticut, Department of Environmental Protection, 1997, Potential Eelgrass Beds Shapefile.

    Online links:
    Type of source media: disc
    Source scale denominator: 24000
    Source contribution:
    This source represents the final form of Potential Eelgrass Beds and was produced from the Potential Eelgrass Beds ArcInfo Coverage.

  2. What changes have been made?

    Date: 1997 (change 1 of 3)
    Feature Creation and Attribution - During the 1993-95 field seasons a team of researchers led by Charles Yarish, equipped with a Global Positioning System (GPS), SCUBA, and a 20' boat surveyed over 800 potential eelgrass locations.  Their GPS coordinates and field notes were used to create a point coverage entitled Eelgrass Sample Points (Source 1), which was plotted and checked on a 1:24000 scale base map of the Connecticut shore.  These point locations, observations, and the nearshore bathymetry were then used to delineate areas representing both observed eelgrass beds (Source 2) and potential eelgrass beds.  Eelgrass beds were initially digitized at 1:24,000 scale, but have been edited and revised on screen at higher resolution.  Potential beds, where not individually delineated, were created by buffering observed beds (Source 2) a distance of 33 feet (10 meters).  These buffered polygons were intersected with buffered (distance of 5 ft.) shoreline arcs to keep potential polygons a minimum distance off the shoreline.  These potential beds are considered to be areas where eelgrass is likely to spread to under ideal conditions, where eelgrass may exist in small isolated patches, where eelgrass may exhibit high temporal variability, or perhaps where restoration projects could be undertaken.

    Person responsible for change:
    Mary DiGiacomo-Cohen
    University of Connecticut, Long Island Sound Resource Center
    860-405-9015 (voice)

    Data sources used in this process:
    • Source 1 - Eelgrass Sample Points Coverage
    • Source 2 - Observed Eelgrass Beds Coverage

    Data sources produced in this process:
    • Source 3 - Potential Eelgrass Beds Coverage

    Date: 1997 (change 2 of 3)
    Datum conversion - Using ESRI ArcInfo software, the Potential Eelgrass Beds layer was converted from the Connecticut State Plane Coordinate System of 1927 (NAD27) to the Connecticut State Plane Coordinate System of 1983 (NAD83). The NADCON (North American Datum CONversion) data transformation was used.
    

    Person responsible for change:
    State of Connecticut, Department of Environmental Protection

    Data sources used in this process:
    • Source 3 - Potential Eelgrass Beds Coverage

    Data sources produced in this process:
    • Source 3 - Potential Eelgrass Beds Coverage

    Date: 1997 (change 3 of 3)
    Using ArcView software, the Potential Eelgrass Beds Coverage was converted to Shapefile format.  

    Person responsible for change:
    State of Connecticut, Department of Environmental Protection

    Data sources used in this process:
    • Source 3 - Potential Eelgrass Beds Coverage

    Data sources produced in this process:
    • Source 4 - Potential Eelgrass Beds Shapefile

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

  1. How well have the observations been checked?

    Attribute accuracy is unknown.

  2. How accurate are the geographic locations?

    The horizontal positional accuracy of this data is unknown.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    The completeness of the data reflects the feature content of the data sources, which includes the GPS data files and field notes.  This layer is complete in the sense that it accurately reflects the contents of the above referenced source information available at the time the State of Connecticut, Department of Environmental Protection created the layer. However, compared to current conditions, this layer is incomplete and is not updated.

  5. How consistent are the relationships among the observations, including topology?

    Logical consistency for this layer is not known.

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How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access constraints: None. The data is in the public domain and may be redistributed.
Use constraints:
None. No restrictions or legal prerequisites for using the data.  Note, the data is not intended for maps printed at map scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet.)  Once acquired, any modification made to the data must be noted in the metadata. When printing this information on a map or using it in a software application, analysis, or report, please acknowledge the State of Connecticut, Department of Environmental Protection as the source for this information.

Distributor 1 of 1

  1. Who distributes the data set?

    State of Connecticut, Department of Enviromental Protection
    79 Elm Street
    Hartford, Connecticut 06106-5127
    USA

    860-424-3034 (voice)
    860-424-4054 (FAX)
    dep.gisdata@ct.gov
    Hours of Service: Monday to Friday, 08:30 to 16:30 Eastern Standard Time

  2. What's the catalog number I need to order this data set?

    Potential Eelgrass Beds

  3. What legal disclaimers am I supposed to read?

  4. How can I download or order the data?

    • Availability in digital form:


    • Data format:
      in format Shapefile, Feature Class (version ArcGIS)
      Network links:http://www.ct.gov/deep

    • Cost to order the data: An online copy of the data may be accessed without charge.


  5. Is there some other way to get the data?

    The data distributor does not provide custom GIS analysis or mapping services. Data is available in a standard format and may be converted to other formats, projections, coordinate systems, or selected for specific geographic regions by the party receiving the data.

  6. What hardware or software do I need in order to use the data set?

    Geographic information sytem (GIS), computer-aided drawing or other mapping software is necessary to display, view and access the information.

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Who wrote the metadata?

Dates:
Last modified: 20120119

Metadata author:
Jacqueline Mickiewicz, Mary DiGiacomo-Cohen
State of Connecticut, Department of Environmental Protection
79 Elm Street
Hartford, Connecticut 06106-5127
USA

860-424-3540 (voice)
860-424-4058 (FAX)
dep.gisdata@ct.gov
Hours of Service: Monday to Friday, 08:30 to 16:30 Eastern Standard Time

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata(FGDC-STD-001-1998)

Metadata extensions used:
  • http://www.esri.com/metadata/esriprof80.html

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