Phragmites 1968 is a 1:12,000-scale, polygon feature-based layer that includes areas where phragmites existed in 1968 along the lower Connecticut River corridor from the towns of Portland and Cromwell south to Long Island Sound. This layer was published at the same time as the Phragmites 1994 layer in order to depict the historic differences in phragmites growth between 1968 and 1994. The Phragmites 1968 layer was compiled using 1:12,000 black and white digital orthophotos obtained in 1968 as part of a Connecticut Department of Environmental Protection aerial mapping survey. This data represents a particular point in time (1968). It is not updated and does not depcit current conditions. Features are polygon locations that represent the approximate location of phragmites growth in 1968. Attribute information is comprised of the NAME68 attribute that identifies one of 25 general locations of phragmites growth. Other attributes include AV_LEGEND that depicts the existence of phragmites, and ACREAGE that depicts the size of each polygon in acres. Data was compiled at a 1:12,000 scale.
For additional information, refer to the complete report generated as a result of the study that commissioned the publication of the Phragmites 1968 and Phragmites 1994 layers. This report is entitled "Spatial Pattern of Phragmites Australis (CAV) Trin ex Steuf. Within the Tidelands of the Connecticut River, 1994" and was authored by Nels Barrett (United States Department of Agriculture Natural Resources Conservation Service, 344 Merrow Road, Suite A., Tolland, Connecticut 06084 USA) and Sandy Prisloe (University of Connecticut Cooperative Extension System, College of Agricultural and Natural Resources, P.O. Box 70, Haddam, CT 06438 USA).
publication date
Phragmites growth in 1968 represented as polygon features. (Source: State of Connecticut, Department of Environmental Protection)
Internal feature number. (Source: ESRI)
Name of location where phragmites exists. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Black Hall River | Black Hall River area |
| Calves Island | Calves Island area |
| Chapman Pond | Chapman Pond area |
| Chester Creek | Chester Creek area |
| Deep River | Deep River area |
| Duck River | Duck River area |
| Essex Middle Cove Complex | Essex Middle Cove Complex area |
| Fenwick | Fenwick area |
| Ferry Point | Ferry Point area |
| Goose Island | Goose Island area |
| Great Island | Great Island area |
| Great Meadow / Essex North Cove | Great Meadow / Essex North Cove area |
| Griswold Point | Griswold Point area |
| Hamburg Cove | Hamburg Cove area |
| Joshua Creek | Joshua Creek area |
| Lieutenant River North | Lieutenant River North area |
| Lieutenant River South | Lieutenant River South area |
| Lord Cove | Lord Cove area |
| North Cove | North Cove area |
| Nott Island | Nott Island area |
| Otter Cove | Otter Cove area |
| Post & Prat Cove | Post & Prat Cove area |
| Ragged Rock Creek | Ragged Rock Creek area |
| Smiths Neck | Smiths Neck area |
| South Cove | South Cove area |
| Upper Island Marsh Complex | Upper Island Marsh Complex area |
Size of feature in acres (Source: State of Connecticut, Department of Environmental Protection)
Feature geometry. (Source: ESRI)
Feature geometry. (Source: ESRI)
Includes Phragmites 1968 features such as the location and size of the polygon. Attributes include AV_LEGEND, which identifies the polygon as phragmites, ACREAGE, which identifies the size of the polygon in acres, and NAME68, which identifies the general location (one of 25 areas) of the feature. This layer is best symbolized as a single feature type.
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Phragmites 1968 is 1:12,000 scale data that depicts the locations of phragmites growth in 1968. Use this layer to show the extent of phragmites growth in 1968 along the lower Connecticut River corridor. In addition, this layer can be used with Phragmites 1994 that depicts the locations of phragmites growth in 1994. The use of both of these layers can more clearly demonstrate the extent of invasive growth of phragmites between 1968 and 1994. Not intended for maps printed at map scales greater or more detailed than 1:12,000 scale (1 inch = 1,000 feet).
The 1968 orthophotos were used as the base map for locating and identifying phragmites and ground control points with the use of a stereoscope.
This source was created by manually interpreting phragmites areas onto mylar that was overlaid onto Source 1, the 1968 digital orthophotos.
After completion of the mylar overlays, the orthophotos and the mylars were scanned and saved at 300 dpi in tagged image file (tif) format.
This data source was created when the tif images in Source 3 were scanned and rectified using established ground control points referenced in Source 1.
This data source refers to all features combined in one statewide layer. Since initial publication in 1995, a subsequent edition of the layer was generated by the State of Connecticut in order to convert from NAD 27 to NAD 83. 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.
Using a stereoscope and the 1:12,000 scale 1968 orthophotos, the phragmites invasive extent was manually interpreted by an ecologist, then transferred along with ground control points, e.g., large boulders, road/stream crossings, intersections, etc., to mylar overlays (Source 2).
The 1968 orthophotos (Source 1) and the mylar overlays (Source 2) were scanned at an optical resolution of 300 dpi and saved as gray-scale images in the tagged image file (tif) format (Source 3).
Using coordinates for the ground control points obtained from Digital Ortho Quarter Quads (DOQQs), the scanned imagery was rectified using Blue Marble Geographics Geographic Transformer software. The registration of each aerial photograph and overlay used anywhere from five to fifty-three control points depending on the distribution of phragmites in the photograph, and was output to Connecticut State Plane Coordinates, NAD 27.
Once the Rectified Scanned Imagery (Source 4) was completed, the images were imported into ArcView 3 software where the boundaries were manually digitized (heads-up digitizing) to create the ArcView shapefile.
Datum conversion - Using DEPGIS Connecticut NADCON Extension for ESRI ArcView 3 software, the Phragmites 1968 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.
The Phragmites 1968 layer retains the feature types and information identified by the State of Connecticut, Department of Environmental Protection and obtained from the 1968 digital orthophotos. Accuracy level of attributes is not known. The AV_LEGEND attribute contains the string "Phragmites" for every feature. The NAME68 field identifies the particular location (25 total locations) of the feature. The ACREAGE attribute is a calculated field that depicts the area in acres of each feature.
Horizontal accuracy of this layer is consistent only with the source data (1:12,000 scale digital orthophotos) from which features were compiled. Feature locations were determined by using a stereoscope with the 1:12,000 orthophotos and identifying ground control points, e.g., large boulders, road/stream crossings, intersections, etc., on the photos. An overall horizontal accuracy level cannot be determined.
The completeness of the data reflects the feature content of the data sources, which include the digital orthophotos (Source 1). The Phragmites 1968 layer is complete in the sense that it accurately reflects 1968 phragmites information available at the time the layer was created. This data is not updated and represents a particular point in time (1968). This data does not represent all of the phragmites in Connecticut.
Polygon features conform to the following topological rules. Polygons are single part. There are no duplicate polygons. Polygons do not self overlap. Polygons do not overlap other polygons. No automated procedures or tests were performed to guarantee desired topology other than visual inspection.
No restrictions or legal prerequisites for using the data. The data is suitable for use at appropriate scale, and is not intended for maps printed at scales greater or more detailed than 1:12,000 scale (1 inch = 1,000 feet). Although this data set has been used by the State of Connecticut, Department of Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Environmental Protection as to the accuracy of the data and or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the State of Connecticut, Department of Environmental Protection in the use of these data or related materials. The user assumes the entire risk related to the use of these data. Once the data is distributed to the user, modifications made to the data by the user should be noted in the metadata. When printing this data 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