Observed Eelgrass Beds is a 1:24,000 scale, polygon feature-based layer that depicts the locations of observed 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 Eelgrass Sample Points layer. 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. Keeping in mind the temporal and spatial variability of eelgrass, beds may vary in size, shape, and density from year to year. 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 Observed Eelgrass Beds layer is not a complete dataset of all observed 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 101 polygon features representing observed eelgrass beds in this layer. Geographic locations are as follows: westernmost areas: Clinton Harbor; easternmost areas: Little Narragansett Bay, Rhode Island waters. Observed beds range in size from .003 acre (131 sq. ft.) to 49 acres (2,136,608 sq. ft.). The total area of observed beds is 632.6 acres.
For more information, refer to the Eelgrass Sample Points and Potential Eelgrass Beds layers.
ground condition
Observed Eelgrass Areas stored as digital vector data (Source: State of Connecticut, Department of Environmental Protection)
Internal feature number. (Source: ESRI)
Feature geometry. (Source: ESRI)
ArcView Legend field (decodes TYPE attribute). Density of the eelgrass bed. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Low | Low density of eelgrass bed. |
| Medium | Medium density of eelgrass bed. |
| High | High density of eelgrass bed |
| Absent | Eelgrass is absent in bed |
Area of feature in acres (SHAPE_AREA divided by 43560). (Source: State of Connecticut, Department of Environmental Protection)
Describes density of the eelgrass bed. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| L | Low density of eelgrass bed. |
| M | Medium density of eelgrass bed |
| H | High density of eelgrass bed |
| A | Absent. Eelgrass is absent. |
Feature geometry. (Source: ESRI)
Number of point locations (Eelgrass Sample Points) within the polygon. (Source: State of Connecticut, Department of Environmental Protection)
Includes Observed Eelgrass Bed polygon features such as eelgrass density (AV_LEGEND), code for eelgrass density (TYPE), point frequency within each polygon (FREQUENCY), size of the feature in acres (ACREAGE), size of the feature in square feet (SHAPE_AREA), and perimeter of feature area (SHAPE_LENGTH). Use the AV_LEGEND attribute to symbolize features by density on a map. The AV_LEGEND attribute decodes the TYPE attribute.
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Observed Eelgrass Beds is 1:24,000-scale data. The purpose of this datalayer is to depict the locations of observed eelgrass along Connecticut's coast. The polygons in this layer were created from the Eelgrass Sample Points layer. 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.)
This source served as the major source of base data for the creation of Observed 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.
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.
This source represents the final form of Observed Eelgrass Beds and was produced from the Observed Eelgrass Beds ArcInfo Coverage.
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.
Datum conversion - Using ESRI ArcInfo software, the Observed 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.
Using ArcView software, the Observed Eelgrass Beds Coverage was converted to Shapefile format.
Attribute accuracy is unknown.
The horizontal positional accuracy of this data is unknown.
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.
Logical consistency for this layer is not known.
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.
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| Data format: | in format Shapefile, Feature Class (version ArcGIS) |
|---|---|
| Network links: | http://www.ct.gov/deep |
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.
79 Elm Street