1880s NOS T-Sheet Wetland Polygon Features is a 1:10,000-scale, polygon feature-based layer that includes information depicting historic wetlands for areas of coastal Connecticut during the 1880s. The layer depicts information found on topographic survey sheets (T-sheets) from the US Coast and Geodetic Survey (USC&GS), a predecessor to the National Ocean Service (NOS). The layer represents conditions at a particular point in time. The layer does not depict current conditions. The layer includes ground condition features such as wetland areas, interior wetland uplands, and interior wetand waterbodies. Semi-submerged marshes, referred to here as "low marshes," ocurring where it is possible to discern marsh-like features waterward of the shoreline are also included. Off shore and riverine islands and rocks may be included depending on the quality of their depiction on the t-sheet. It does not include any non wetland-centric elements that may have been depicted on the t-sheets such as buildings, roads, bridges, etc., nor does it include other off-shore features like mud flats, tidal flats, etc. Features are polygon locations that represent the approximate location of wetland areas and internal wetland features such as uplands or waterbodies. Shoreline, as depicted on the T-sheets that pre-date 1927, reference an approximation of Mean High Water (MHW). Although MHW is technically determined by averaging the height of the high water line, (HWL) the landward extent of the last high tide over a 19 year lunar cycle, USC&GS topographers appoximated MHW by familarizing themselves with the tidal conditions in a given area and noting the assorted physical characteristics of the beach. (For a more complete description of this and other shoreline indicators, the reader is directed to the following article: "Historical Shoreline Change: Error Analysis and Mapping Accuracy," Crowell, M., Leatherman, S., and Buckley, M. Journal of Coastal Research, Vol 7, No. 3, 1991, pp 839-852.) Attribute information is comprised of codes to identify individual features, encode wetland feature type information, and cartographically represent (symbolize) wetland features on a map. These codes were derived in part from the National Oceanic & Atmospheric Administration (NOAA) Coastal Services Center (CSC) Historic Digital Shoreline Capture project and modified by the State of Connecticut Department of Environmental Protection to address the inclusion of wetland areas. This data was compiled at 1:10,000 scale. This data is not updated.
ground condition
arc attribute table (Source: ESRI)
Internal feature number. (Source: ESRI)
Feature geometry. (Source: ESRI)
Abbreviation for Feature Code. A number field that provides classification for types of shoreline features. (Source: NOAA, modified by State of Connecticut, Department of Environmental Protection as needed)
| Value | Definition |
|---|---|
| 55 | Marsh/Wetlands: see corresponding DECODE value for complete definition |
| 66 | Interior Wetland Waterbodies: see corresponding DECODE value for complete definition |
| 77 | Interior Wetland Uplands: see corresponding DECODE value for complete definition |
| 44 | Low Marsh: see corresponding DECODE value for complete definition |
A text field that provides the english language equivalent of the F_CODE values (Source: NOAA, modified by the State of Connecticut, Department of Environmental Protection as needed)
| Value | Definition |
|---|---|
| Marsh/Wetlands | Areas of marsh/wetlands landwards of the referenced shoreline as indicated on T-sheets |
| Interior Wetland Waterbodies | Areas of apparent waterbodies within the boundaries of a marsh/wetland polygon |
| Interior Wetland Uplands | Areas of apparent uplandswithin the boundaries of a marsh/wetland polygon |
| Low Marsh | Areas of semi-submerged wetland features (waterward of the shoreline/wetland shoreline) |
ArcView Legend. A text field for symbolizing different feature types on a map. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Marsh/Wetlands | see corresponding DECODE value for complete definition |
| Interior Wetland Waterbodies | see corresponding DECODE value for complete definition |
| Interior Wetland Uplands | see corresponding DECODE value for complete definition |
| Low Marsh | see corresponding DECODE value for complete definition |
Internet Mapping Software Legend. A text field for classifying and symbolizing feature types in a simple manner for an Internet map. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Marsh/Wetlands | see corresponding DECODE value for complete definition |
| non-wetland features | An aggregate of the DECODE values "interior wetland waterbodies" and "interior wetland uplands" |
| Low Marsh | see corresponding DECODE value for complete definition |
Sheet Number. A text field providing the NOS numeric designation of the T-sheet. Taken from the T-sheet label. Multiple sheet numbers are included where lines have been edgematched across sheets. (Source: NOAA)
Sheet Name. A text field providing the NOS naming designation of the T-sheet. Taken from the T-sheet label. Multiple sheet names are addressed as "Multiple sheets" where lines have been edgematched across sheets. (Source: NOAA)
A text field providing the date or range of dates corresponding to the survey. Taken from the T-sheet label. Multiple sheet dates are included where lines have been edgematched across sheets. (Source: NOAA)
A text field providing the denominator value of the scale of the T-sheet. Taken from the T-sheet label. (Source: NOAA)
Calculated length of feature in feet. Note, LENGTH_FT values are not automatically updated after modifying feature geometry (shape). Values must be recalculated after features are edited, simplified, generalized, clipped, dissolved, etc. (Source: State of Connecticut, Department of Environmental Protection)
| Range of values | |
|---|---|
| Units: | feet |
Calculated length of feature in miles. Note, LENGTH_MI values are not automatically updated after modifying feature geometry (shape). Values must be recalculated after features are edited, simplified, generalized, clipped, dissolved, etc. (Source: State of Connecticut, Department of Environmental Protection)
| Range of values | |
|---|---|
| Units: | miles |
Calculated area of feature in acres. Note, LENGTH_MI values are not automatically updated after modifying feature geometry (shape). Values must be recalculated after features are edited, simplified, generalized, clipped, dissolved, etc. (Source: State of Connecticut, Department of Environmental Protection)
| Range of values | |
|---|---|
| Units: | acres |
Calculated area of feature in square miles. Note, LENGTH_MI values are not automatically updated after modifying feature geometry (shape). Values must be recalculated after features are edited, simplified, generalized, clipped, dissolved, etc. (Source: State of Connecticut, Department of Environmental Protection)
| Range of values | |
|---|---|
| Units: | square miles |
An integer field indicating whether or not a line has been affected by the edgematching process (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 999 | polygonwas not edgematched |
| 1 | polygon was added/merged as part of edgematching process |
A text field providing the name of the State a feature is located in (Source: Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| NY | New York |
| CT | Connecticut |
| RI | Rhode Island |
Feature geometry. (Source: ESRI)
Calculated value for the estimated horizontal positional error. To be read in a "+/-" format. (Source: "Historical Shoreline Change: Error Analysis and Mapping Accuracy," Crowell, M., Leatherman, S., and Buckley, M. Journal of Coastal Research, Vol 7, No. 3, 1991, pp 839-852 & CT DEP analysis.)
| Value | Definition |
|---|---|
| 27.6 | Units, in feet, of error for shoreline and wetland features not including those that were edgematched or depict low-marsh |
| 28.3 | Units, in feet, of error for shoreline and wetland features that were edgematched |
| 40.1 | Units, in feet, of error for shoreline and wetland features that depict low-marsh |
Includes 1880s NOS T-Sheet Wetland Polygon Features layer features such as wetland polygons, wetland upland boundaries, and wetland interior boundaries. Information encoded about these features includes types, names, measurement information, and standard cartographic symbology classification schemes. Use the DECODE values to uniquely identify and label features. Use the AV_LEGEND attribute to symbolize features by type on a map. Use the IMS_LEGEND attribute to more generally symbolize the features by type. To define a layer that only includes a certain type of feature, query 1880s NOS T-Sheet Wetland Polygon Features layer features for the DECODE required values. STATE provides a way to select out shoreline for either NY, CT, or RI. (NOTE: NY and RI only include small areas of Rye and Westerly.) ERROR_FT provides the estimated worst-case root mean square (RMS) error values for the wetland features and should be considered as "+/-" values if used in a buffering analysis. Values for SHEET_NO, SHEET_NAME, SHEET_DATE, SCALE, and ERROR_FT are the same for all records and relate information on the T-sheet they were derived from, unless the records were involved in edgematching. In these cases the values for all applicable sheet numbers and dates were added. Sheet names were were not added due to field lenght limits and were coded as "multiple sheets." ERROR_FT values were updated with values incorporating edgematching errors.
Examples of shoreline feature codes can be found in "Creating Vector-Based Shoreline Coverages from T-sheets: A Vectorization Manual" prepared by the NOAA Coastal Services Center. (http://www.csc.noaa.gove/shoreline/pdf/vmanual.pdf) Where appropriate, codes were added/modified to suit the needs of the State of Connecticut, Department of Environmental Protection.
Martyn Smith and Dr. Robert Cromley (University of Connecticut Center for Geographic Information and Analysis) for completing the T-Sheet georeferencing, line vectorization, and creation of the GIS data layer. Mary DiGiacomo-Cohen (Long Island Sound Resource Center) provided critical assistance including data quality reviews and feature attribution. Kevin O'Brien (State of Connecticut, Department of Environmental Protection) assisted with data quality reviews, feature attribution, shoreline/wetland geodatabase feature class creation and topologic validation, and creating low-marsh features. Ron Rozsa (State of Connecticut, Department of Environmental Protection) was project coordinator.
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1880s NOS T-Sheet Wetland Polygon Features is 1:10,000-scale data. It depicts the location of historic wetland features for all of coastal Connecticut with the exception of the area of New Haven Harbor from the West River in West Haven to the New Haven/East haven town boundary. The features also extend slightly beyond the Connecticut state lines into Rye, New York and Westerly, Rhode Island. Use this layer to display historic wetlands. Since this data may be considered a crucial element in land use planning, determination of boundary extents, performing change studies for erosion and accretion examinations and other types of decision making this layer may also be used for analytic purposes. Use this layer with other 1:10,000-scale map data such as any other NOS T-sheet Shoreline or Wetland layers. Not intended for maps printed at map scales greater or more detailed than 1:10,000 scale (1 inch = 833.33 feet.)
Staff from the US National Geodetic Survey (NGS) provided 17 scanned JPEG images at 1200 pixels per inch (ppi) based on the original paper/mylar 1:10,000 scale T-sheet to the State of Connecticut Department of Environmental Protection. These served as the source for the georeferenced images used in the shoreline digitization.
The resulting 17 shoreline shapefiles that were produced from the vectorization process and used in the QA/QC, attributing, and feature class creation steps.
These are the 17 *.TIFF image derived from the Original T-Sheet Images that were used as a base during the digitization process as well during the QA/QC review, attribution, and edgematching.
The resulting 17 wetland polygon shapefiles that were produced from the vectorization process and used in the QA/QC, attributing, and feature class creation steps.
This is the ArcGIS geodatabase feature class containing the topology rules used during the edgematching.
The data resulting from creating an ArcGIS feature class and loading the original 17 shoreline shapefiles into it. Used within a geodatabase with a topology feature class for edgematching.
The data resulting from creating an ArcGIS feature class and loading the original 17 wetland polygon shapefiles into it. Used within a geodatabase with a topology feature class for edgematching.
A feature class consisting of points created from the wetland polygon feature class used to hold and transfer attributes from the original polygons to any new ones that might need to be created to replace the old ones.
Georeferencing Imagery: JPEG images were converted to uncompressed/RGB 8-bit TIFF format in Adobe Photoshop 6.0. Images were then georeferenced to native coordinate system (NAD27 GCS) using Blue Marble Geographics Geographic Transformer 5.0. Control points at latitude/longitude intersections were identified and selected on each image. All transformed images were saved in TIFF formats with appropriate world file header information. TIFF Images were then converted to ESRI GRID format using ArcToolbox (version 8.3) and optimized for use with ArcScan (version 8.3). ESRI GRID. NAD 27 GCS coordinate system was defined for these ESRI GRID files. ESRI GRID files in NAD27 GCS were then reprojected to NAD83 CT State Plane coordinate system using ArcToolbox (version 8.3). ESRI GRID files were then converted to TIFF files with world file header information.
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Shoreline/Wetland Vectorization: All lines representing wetlands were vectorized to the neatline or edge of the original shoreline map. All wetland areas (including internal upland and waterbody features) have been vectorized. Features were assigned F_CODE values derived from NOAA CSC protocols. In general the vectorization process followed the guidelines specified in "Creating Vector-Based Shoreline Coverages from T-sheets: A Vectorization Manual" prepared by NOAA. (http://www.csc.noaa.gove/shoreline/pdf/vmanuel.pdf)
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Shapefile Data QA/QC & Attribution Updates: Shoreline and wetland line features from the Shoreline Feature Layer and the Wetland Polygon Layer were overlaid onto the Georeferenced T-sheet Image by staff from the Long Island Sound Resources Center and the State of Connecticut Department of Environmental Protection. The QA/QC process took three distinct steps, Attribute Checking, Geometry Checking, and Attribute Updates, described below: Step 1 - Attribute Checking: F_CODE values for the Shoreline Feature Layer and the Wetland Polygon Layer were symbolized and compared to the features depicted on the Georeferenced T-sheet Image to assess whether or not the lines and polygons were symbolized correctly. In cases where the lines or polygons needed correction, this was achieved through record selection and field calculations using ArcGIS software. In general, the concept of interpreting the type of shoreline and wetland features is largely subjective. Features types such as wetland shoreline are generally straight-forward. Wetland boundary lines and their associated polygons are more subjective, due in large part to the clarity of the image in these areas due to cross-hatching and shading techniques used by the cartographers. Although consistent results were strived for, it should be noted that in all cases these feature attributes are best guess assessments. There may be certain, slight inconsistencies in attribute values from sheet to sheet due to a number of factors including, but not limited to, the individual reviewer's interpretation, the clarity and quality of the t-sheet image, etc. Step 2 - Geometry Checking: Essentially this process was a dual attempt to a) ensure the proper representation of the shoreline & wetland features from the Georeferenced T-sheet Image to the Shoreline Feature Layer and the Wetland Polygon Layers, and b) impart as much topological intergrity between the Shoreline Feature Layer and the Wetland Polygon Layer as possible with a manual review. It should be re-emphasized here that there is no true topology in the strictest sense within these layers, but rather a modicum of coincidence among the line and polygon features. In case a), features from the Shoreline Feature Layer and the Wetland Polygon Layers were compared on-screen to the Georeferenced T-sheet Image. In areas where features needed to be added or removed, the appropriate actions were taken in ArcGIS. In situations where features need to be added, snapping among and between line and polygon layers was used to maximize de-facto topology. In general, the largest area of editing dealt with inconsistencies in capturing/omitting narrow ditches usually within wetlands. As a rule, these were eliminated in the QA/QC process so that only "natural" hydrologic stream/river features were retained. (Typically these ditches were very linear in nature and thus easy to identify.) In case b), a manual visual inspection during the entire QA/QC process was used to look for places where the line and polygon features were not coincident, or where a polygon had small internal polygons as a result of deleting uneccesary lines, either from case a) or as artifacts from the original vectorization. In many cases these areas presented themselves in readily identifiable areas, such as in narrow meandering streams. Corrections generally took the form of the easiest adjustment to make; in some cases it was snapping polygons to lines, and in other cases the reverse. Typically these adjustments were on the order of 5 ft or less, so the holding of one feature over the other was deemed unecessary. In taking care of internal polygons, the ArcGIS Merge function was used to combine multiple polygons. As a cautionary note, care was taken to be as thorough as possible, but it is likely that there were areas that were missed. Step 3 - Attribute Updates: Once all the geometric edits were complete, the attributes were rechecked for coding updates as well as measurement field updates. Finally the fields providing T-sheet information (SHEET_NO, SHEET_NAME, SHEET_DATE, SCALE, and ERROR_FT) were added and attributed for all records at once.
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Geodatabase Creation: Using ESRI ArcGIS 9.0, a geodatabase was created to compile and process the shoreline and wetland polygon shapefiles created in the previous steps into statewide data layers depicting historic 1880 shoreline and wetland features. The spatial extent was set to encompass the entire State of Connecticut, a feature dataset was created to hold the feature classes into which the 17 shoreline and 17 wetland polygon shapefiles were loaded. Topology was generated to ensure proper geometric integrity within and between the feature classes. The following topological rules were instituted: Line features conform to the following topological rules. Lines do not have dangles. Lines do not self-intersect. Lines do not overlap. Lines do not self intersect. Polygons must not overlap. Boundaries of polygons musy be covered by lines from the Shoreline feature class. In addition, a point feature class was created from the polygons to facilitate the transfer of attributes from original polygons to any new ones that might have been created as replacements for the originals.
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Feature Class Edits: Shoreline, wetland, wetland points, and topology feature classes were overlaid onto the Georeferenced T-sheet Images within ArcGIS for the purpose of editing into edgematched, topologically valid statewide shoreline and wetland feature classes. Upon inspecting the topology errors, it was evident that there were many areas where lines and polygons were not coinicident. As such it was decided to reconcile the line work first, then use the corrected lines to recreate any invalid polygons. Attributes from the original polygons captured in the wetland point feature class would then be transfered to the recreated polygons. The feature class editing process thus took three distinct steps: Shoreline Feature Edgematching/Topology Validation, Wetland Polygon Feature Edgematching/Topology Validation, and Final Inspection, described below: 1) Shoreline Feature Edgematching/Topology Validation: Using the Georeferenced T-sheet imagery and the shoreline feature class, areas of overlapping linework between sheets was identified. A visual inspection of the conflicting data was performed to determine which data to keep, delete or adjust, as well as what editing methods were most appropriate. In general, the edgematch functionality on the ArcGIS Advanced Editing toolbar caused significant shifting/movement in the line work and was only used sparingly. Typical editing options included deleting lines from one sheet and adding arcs to connect the remaining edges to data from the adjacent sheet, or deleting part of the line work from each sheet and adding intermediate connector lines. In any case, an attribute field, EDGEMATCH, was added to the feature class track any changes to the lines. Lines with values of 999 had no edgematching applied; Lines with values of 1 indicate a connector arc(s) was/were added; Lines with values of 2 were moved due to the edgematching. Additionally, all fields realting to the T-sheet (SHEET_NO, SHEET_NAME, and SHEET_DATE) were updated to reflect the inclusion of multiple sheet data. Any lines that were added were given an F_CODE value consistent with its representation on the Georeferenced T-sheet. Once the shoreline features were edgematched into an single statewide layer, the line topology rules were run. Each error was manually zoomed to for visual inspection and either corrected (via manual editing functions such as extend, trim, split/delete, or modify features), or marked as an excpetion. Typical causes of exceptions were dangles that represented the cartographic termination of a waterbody or shoreline at the edge of a t-sheet that had no adjacent sheet. After any corrections the topology was re-validated to ensure the corrections were successful. After the edgematching/topology validation process, all length fields were recalculated to account for alterations from the editing processes 2) Wetland Polygon Feature Edgematching/Topology Validation: Once the line work was completely validated, wetland polygons were adressed both for edgematching and topology. The topology was rerun to address areas of problems with the lines and polygons. In almost all cases where polygons needed to be edgematched or undergo a topological correction, the offending polygon(s) was/were deleted and rebuilt using the validated line work. In a few cases, the corrections were easy enough to fix using manual editing functions such as split/delete, modify features, or merge. The wetland polygon point layer was then used to manually transfer the attributes from the original polygon to the new one. As in the shoreline feature class, the EDGEMATCH field was used to track polygons that underwent edgematching. Polygons with values of 999 had no edgematching applied; Polygons with values of 1 indicate the polygon was created using arcs that were edgematched or two or more polygons were merged together. After any corrections the topology was re-validated to ensure the corrections were successful. Additionally, all fields relating to the T-sheet (SHEET_NO, SHEET_NAME, and SHEET_DATE) were updated to reflect the inclusion of multiple sheet data. Any polygons that were added in addition to the existing ones (i.e a polygon was discovered to have been missed) were given an F_CODE value consistent with its representation on the Georeferenced T-sheet. After the edgematching/topology validation process, all length and area fields were recalculated to account for alterations from the editing processes. 3) Final Inspection: Once the shoreline and wetland polygon feature classes had valid topologies, afinal insepction was performed to ensure all lines were coded properly. F_CODE values for the Shoreline feature class and the Wetland Polygon feature class were symbolized and compared to each other and to the features depicted on the Georeferenced T-sheet Images to assess whether or not the lines and polygons were symbolized correctly. In cases where the lines or polygons needed attribute correction, this was achieved through record selection and field calculations using ArcGIS software.
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Addition of Low Marsh Features: Shoreline, wetland, and topology feature classes were overlaid onto the Georeferenced T-sheet Images within ArcGIS for the purpose of adding into the edgematched, topologically valid statewide shoreline and wetland feature classes data representing the locations of "low marshes" or areas depicted as marsh-like water ward of the shoreline. The feature class editing process thus took four distinct steps: Digitizing Low Marsh Features, Creating Low Marsh Wetland Polygon Features, Topology Validation, and Final Inspection, described below: 1) Digitizing Low Marsh Features: Using the Georeferenced T-sheet imagery and the shoreline feature class, areas the boundaries depicting the areas of low marsh were digitized. These areas were not as well defined as other shoreline features and typically appeared as marsh-like cross-hatching with no definitive boundary. As such, error estimates for these line were incresed. During the digitizing process several fields realting to the T-sheet (SHEET_NO, SHEET_NAME) were updated to reflect the inclusion of multiple sheet data. Any lines that were added were given an F_CODE value consistent with its representation on the Georeferenced T-sheet. 2) Creating Low Marsh Wetland Polygon Features: Using the line work for the low marsh features, corresponding polygons were created by using an ArcGIS 9.0 extension, X-Tools, to convert the lines to polygon features. These were then copied into the wetland polygon feature class. After the copy, several fields realting to the T-sheet (SHEET_NO, SHEET_NAME) were updated to reflect the inclusion of multiple sheet data. Any polygons that were added were given an F_CODE value consistent with its representation on the Georeferenced T-sheet. 3)Topology Validation: Once the low marsh line an dpolygon features were digitized, the line/polygon topology rules were run. Each error was manually zoomed to for visual inspection and either corrected (via manual editing functions such as extend, trim, split/delete, or modify features), or marked as an excepetion. After any corrections the topology was re-validated to ensure the corrections were successful. 4) Final Inspection: Once the shoreline and wetland polygon feature classes had valid topologies, a final insepction was performed to ensure all lines were coded properly. F_CODE values for the low marsh records in the Shoreline feature class and the Wetland Polygon feature class were symbolized and compared to each other and to the features depicted on the Georeferenced T-sheet Images to assess whether or not the lines and polygons were symbolized correctly. In cases where the lines or polygons needed attribute correction, this was achieved through record selection and field calculations using ArcGIS software. Other fields providing T-sheet descriptions were checked and updated as well. The new error estimates for low marsh features were added, and new field, STATE, was added to allow the selection of data for either CT, RI, or NY. Finally, all length and area fields were recalculated to account for alterations from the editing processes.
Metadata imported.
Dataset copied.
The 1880s NOS T-Sheet Wetland Polygon Features layer retains the feature types and information identified by the University of Connecticut Center of Geographic Information and Analysis and the State of Connecticut, Department of Environmental Protection (based on NOAA CSC protocols) and vectorized from the georeferenced NOS T-sheets. All attributes have valid values. Values are within defined domains. The accuracy test for the F_CODE attribute values was conducted by comparing the wetland boundary information presented in the source data with interactive displays of the 1880s NOS T-Sheet Wetland Polygon Features layer data on a computer graphic system. These computer displays depicted and labeled the 1880s NOS T-Sheet Wetland Polygon Features in different colors based on F_CODE values for comparison with the original data source. The DECODE values are the English language equivalent of (decodes) the F_CODE field values. AV_LEGEND and IMS_LEGEND are broad classifications of 1880s NOS T-Sheet Wetland Polygon Features. DECODE, AV_LEGEND, and IMS_LEGEND were manually entered. These fields were populated by selecting the appropriate F_CODE types and calculating the corresponding values for each code. The fields SHEET_NO, SHEET_NAME, SHEET_DATE, SCALE and ERROR_FT were calculated by selecting all records regardless of F_CODE designation and calculating a value, except in cases of edgematching where records may contain information realting to several T-sheets. STATE indicates whether a feature is part of New York, Connceticut, or Rhode Island, as the T-sheets overlap state boundaries. Measurement fields were calcluated for all records. LENGTH_FT was calculated by returning the native units (feet), LENGTH_MI was calculated by dividing the native units (feet) by 5280. AREA_ACRES was calculated by returning the square footage divided by 43,560 and AREA_SQMI was calculated by returning the square footage divided by (5280^2). ERROR_FT provides the estimated worst-case root mean square (RMS) error values (in feet) for the wetland features and should be considered as "+/-" values if used in a buffering analysis. EDGEMATCH provides an indication of whether or not a line was adjusted in the edgematching process that pieced this feature layer together from the original, individual NOS T-Sheet data layers. In general, the concept of interpreting the type of wetland features is largely subjective. Features types such as wetland shoreline are generally straight-forward. Wetland upland boundaries are more subjective, due in large part to the clarity of the imagery in these areas due to cross-hatching and shading techniques used by the cartographers. In areas of edgematching lines may not coincide with data from T-sheets. Although consistent results were strived for, it should be noted that in all cases these feature attributes are best guess assessments. There may be certain, slight inconsistencies in attribute values from sheet to sheet due to a number of factors including, but not limited to, the individual reviewer's interpretation, the clarity and quality of the t-sheet image, etc.
The horizontal positional accuracy of this data is estimated. All of the locations are within +/- 27.6 feet of their real world location except edgematched features which are estimated at +/-28.3 feet, and low marsh features, which are estimated at +/- 40.1 feet.
none
The completeness of the data reflects the feature content of the data sources, which include the wetland features depicted on georeferenced images of the scanned original NOS paper or mylar T-sheets. 1880s NOS T-Sheet Wetland Polygon Features layer is complete in the sense that it accurately reflects the contents of the wetland information available at the time the NOS T-Sheets were created. However, compared to current conditions, the 1880s NOS T-Sheet Wetland Polygon Features layer is incomplete. Further, while the data depicts the location of historic wetland features for coastal Connecticut, the area of New Haven Harbor from the West River in West Haven to the New Haven/East haven town boundary is not accounted for due to missing T-sheets. This data is not updated.
All polygons representing wetlands (both land and waterward of the shoreline) were vectorized to the neatline or edge of the original shoreline map. Post-processing edgematching resolved areas of overlap or non-connectivity. Polygon features conform to the following topological rules. Polygons do not overlap. Polygon boundaries must be covered by the features in the Shoreline Feature class. Any deviations from these rules has been inspected and marked as a known exception within the topology feature class. Establishment of logical consistency was performed by the State of Connecticut, Department of Environmental Protection using ESRI ArcGIS software to manually create and control feature topology in geodatabase format. The ESRI ArcGIS validate topology methods were used to identify and inspect errors associated with the above rules. In case where corrections were needed, the most appropriate ArcGIS editnig methodolgy was employed. After all corrections and exceptions were identified, the topology was re-validated to ensure no errors remained.
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 1:10,000 scale (1 inch = 833.33 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. These data are not for navigational purposes.
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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.
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