Eelgrass Sample Points is a 1:24,000-scale, point feature-based layer that depicts the locations where eelgrass (Zostera marina) was either observed or where a location would be potentially favorable for future eelgrass growth. Sample points were taken along Connecticut's coast in Long Island Sound, and in major bays, harbors and rivers along the shoreline. The point features in this layer were compiled from field research using global positioning system (GPS) equipment. Feature locations were not always exact due to equipment failure or lack of satellite reception. In those cases, points were estimated from field notes. Some point locations were corrected based on field notes or hydrography and bathymetry conditions at the sample point location. The number of field points that were altered were as follows: In 1993, 32 of 290 points (11%); in 1994, 93 of 454 points (20%); in 1995, 37 of 105 points (35%). Data compilation occurred on 17 days between 7/21/1993 and 11/16/1995; exact dates of each source's data collection are noted in the attribute table. A total of 849 point locations were surveyed. The westernmost point is Frash Pond in Stratford, Connecticut and the easternmost point is the Pawcatuck River on the Connecticut/Rhode Island Border. Eelgrass was found at 484 locations and was described as either high, medium, or low density, or simply as present or absent. Eelgrass was absent at 365 locations. Publication of the datalayer was in 1997. This layer is not updated. This layer does not represent current conditions.
For more information on the eelgrass polygon layers created from this layer, refer to the metadata for Observed Eelgrass and Potential Eelgrass layers.
publication date
Eelgrass Sample Points stored as digital vector data (Source: State of Connecticut, Department of Environmental Protection)
Internal feature number. (Source: ESRI)
Feature geometry. (Source: ESRI)
Date that the data was collected. (Source: State of Connecticut, Department of Environmental Protection)
A general description of field location. (Source: State of Connecticut, Department of Environmental Protection)
Degrees latitude, as recorded from GPS. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 41 | Latitude degrees of all points |
Minutes latitude, as recorded from GPS. (Source: State of Connecticut, Department of Environmental Protection)
Degrees longitude, as recorded from GPS. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 72 | Longitude degrees of all points. |
Minutes longitude, as recorded from GPS. (Source: State of Connecticut, Department of Environmental Protection)
Describes density or presence of eelgrass bed. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| A | Absent |
| P | Present |
| H | High Density |
| M | Medium Density |
| L | Low Density |
Approximate depth in meters, as measured by divers, not corrected for tides. (Source: State of Connecticut, Department of Environmental Protection)
Approximate time as recorded in field based on a 12 hour clock. (Source: State of Connecticut, Department of Environmental Protection)
Field Comments. May describe condition of eelgrass, more detailed location, bottom type, salinity, associated flora and fauna, in particular, ruppia maritima. (Source: State of Connecticut, Department of Environmental Protection)
Seaweed noted as absent or present or contains up to 5 abbreviated names of seaweeds for each feature. (Source: State of Connecticut, Department of Environmental Protection)
Plotted location point type. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| O | Original point location. |
| A | Altered point location |
Two digit year (extracted from Date field). (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 93 | Year of data collection in YY format. |
| 94 | Year of data collection in YY format. |
| 95 | Year of data collection in YY format. |
Includes Eelgrass Sample point features such as data collection date, location of points, latitude and longitude degrees and minutes, density of eelgrass, depth, time of data recording, comments, types of seaweed in area, plotted location, observed eelgrass polygon id and potential eelgrass polygon id. Features can be symbolized by the Density attribute, which describes the pervasiveness of eelgrass at a particular point location. A single point symbology can also be used whereby no classifications or unique features are displayed.
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The purpose of this datalayer is to depict the point locations of observed eelgrass and potential eelgrass growth along Connecticut's coast and in Long Island Sound. The polygon layers created from these points are the Observed and Potential 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.)
The GPS data that was collected during the creation of this layer also included field notes and corrections to some GPS point locations that were not accurately depicted due to equipment malfunction or satellite reception loss.
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 Eelgrass Sample Points and was produced from the Eelgrass Sample Points ArcInfo Coverage.
Feature digitizing and attribution (GPS method) - During the 1993-1995 field seasons a team of researchers lead by Dr. Charles Yarish of the University of Connecticut Dept. of Ecology and Evolutionary Biology surveyed over 800 potential eelgrass locations along the Connecticut coast using a Global Positioning System (GPS), SCUBA, and a 20' boat. The GPS system used was not explicitly recorded. Their GPS coordinates and field notes were used to create a GIS point coverage which was plotted and checked on a 1:24,000 scale base map of the Connecticut shore. These point locations and field observations, in conjunction with the nearshore bathymetry, were then used to delineate areas representing both observed and potential eelgrass beds. The sample points represent GPS collected Latitude/Longitude coordinates (in decimal minutes) that were projected to Connecticut State Plane coordinates and plotted on 1:24,000 scale digital hydrography and bathymetry layers. Where the original coordinates (hand-recorded) appeared to be in error (due to either human error, bad satellite reception, or inconsistency with the 1:24,000 scale hydrography or bathymetry) the location of the point was altered (based on field note descriptions and memory) to fit the hydrography. Points are noted in the PLOT_LOC attribute as altered or original.
Datum conversion - Using ESRI ArcInfo software, the Eelgrass Sample Points 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.
79 Elm Street
Using ArcView software, the Eelgrass Sample Points Coverage was converted to Shapefile format.
Attribute accuracy is unknown.
Horizontal accuracy is unkown for this layer. However, the data in this layer is only as accurate as the global positioning satellite (GPS) system used to compile the data. The majority of points were compiled with GPS; some were altered and re-plotted due to equipment malfunction or satellite reception problems. The PLOT_LOC attribute denotes whether or not a point feature was altered.
The completeness of the data reflects the feature content of the data sources, which includes the GPS data files and field notes. The Eelgrass Sample Points 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 of this layer is unknown.
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