This data set shows all of the wetlands that are located in Worcester County, Maryland. National Wetland Inventory (NWI) digital data files are records of wetlands location and classification as defined by the U.S. Fish & Wildlife Service. This dataset is one of a series available in 7.5 minute by 7.5 minute blocks containing ground planimetric coordinates of wetlands point, line, and area features and wetlands attributes. When completed, the series will provide coverage for all of the contiguous United States, Hawaii, Alaska, and U.S. protectorates in the Pacific and Caribbean. The digital data as well as the hardcopy maps that were used as the source for the digital data are produced and distributed by the U.S. Fish & Wildlife Service's National Wetlands Inventory project.
The data set provides consultants, planners, and resource managers with information on wetland location and type. The data were collected to meet U.S. Fish & Wildlife Service's mandate to map the wetland and deepwater habitats of the United States.
Many of the attributes for this data are left blank in this metadata due to the complexity of the classification systems that are used, any information that is not provided here can be obtained by going to the United States Fish and Wildlife website located at www.fws.gov/nwi/ The classification information is available at: http://wetlandsfws.er.usgs.gov/nwi/misc_docs/mapcodeslegend.pdf
source photography date
Federal, State, and local regulatory agencies with jurisdiction over wetlands may define and describe wetlands in a different manner than that used in this inventory. There is no attempt, in either the design or products of this inventory, to define the limits of proprietary jurisdiction of any Federal, State, or local government or to establish the geographical scope of the regulatory programs of government agencies. Persons intending to engage in activities involving modifications within or adjacent to wetland areas should seek the advice of appropriate Federal, State, or local agencies concerning specified agency regulatory programs and proprietary jurisdictions that may affect such activities.
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Attribute accuracy is tested by manual comparison of the source with hard copy printouts and/or symbolized display of the digital wetlands data on an interactive computer graphic system. In addition, WAMS software (USFWS-NWI) tests the attributes against a master set of valid wetland attributes.
Polygons intersecting the neat line are closed along the border. Segments making up the outer and inner boundaries of a polygon tie end-to-end to completely enclose the area. Line segments are a set of sequentially numbered coordinate pairs. No duplicate features exist nor duplicate points in a data string. Intersecting lines are separated into individual line segments at the point of intersection. Point data are represented by two sets of coordinate pairs, each with the same coordinate values. All nodes are represented by a single coordinate pair which indicates the beginning or end of a line segment. The neat line is generated by connecting the four corners of the digital file, as established during initialization of the digital file. All data crossing the neat line are clipped to the neat line and data within a specified tolerance of the neat line are snapped to the neat line. Tests for logical consistency are performed by WAMS verification software (USFWS-NWI).
All photo-interpretable wetlands are mapped. In the treeless prairies, 1/4 acre wetlands are mapped. In forested areas, small open water and emergent wetlands are mapped. In general, the minimum mapping unit is from 1 to 3 acres depending on the wetland type and the scale and emulsion of the source aerial photography. In regions of the country where evergreen forested wetlands predominate, wetlands smaller than 3 acres may not be mapped. Thus, a detailed on the ground and historical analysis of a single site may result in a revision of the wetland boundaries established through photographic interpretation. In addition, some small wetlands and those obscured by dense forest cover may not be included in this dataset.
wetlands spatial and attribute information
base cartographic data
wetlands location and classification
NWI maps are compiled through manual photo interpretation of NHAP or NAPP aerial photography supplemented by Soil Surveys and field checking of wetland photo signatures. Delineated wetland boundaries are manually transferred from interpreted photos to USGS 7.5 minute topographic quadrangle maps and then manually labeled. Quality control steps occur throughout the photo interpretation, map compilation, and map reproduction processes.
7206 National Seashore Lane
Digital wetlands data are either manually digitized or scanned from stable-base copies of the 24,000 scale wetlands overlays registered to the standard U.S. Geological Survey (USGS) 7.5 minute quadrangles into topologically correct data files using Wetlands Analytical Mapping System (WAMS) software. Files contain ground planimetric coordinates and wetland attributes. The quadrangles were referenced to the North American Datum of 1927 (NAD27) horizontal datum. The scanning process captured the digital data at a scanning resolution of at least 0.001 inches; the resulting raster data were vectorized and then attributed on an interactive editing station. Manual digitizing used a digitizing table to capture the digital data at a resolution of at least 0.005 inches; attribution was performed as the data were digitized. The determination of scanning versus manual digitizing production method was based on feature density, source map quality, feature symbology, and availability of production systems. The data were checked for position by comparing plots of the digital data to the source material.
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The Maryland Coastal Bays Program has reprojected NATIONAL WETLANDS INVENTORY (NWI) data which was received from the U.S. Fish & Wildlife Service, the data producer and custodian. The coordinate system has been changed to Maryland State Plane NAD27 fipszone 1900 as well as UTM NAD83 zone 18. These changes were performed using UNIX ARC/INFO 7.1.1 - PROJECT command.. Additional conversions have also been performed on the NATIONAL WETLANDS INVENTORY (NWI) data for use in the Worcester County/Maryland Coastal Bays Watershed. (1) The dataset, originally provided by the U.S. Fish & Wildlife Service in several small sections in dlg format, has been merged to a single dataset including only area within Worcester County and the area within the Coastal Bays watershed. This was accomplished by using the MAPJOIN and CLIP commands in A/I with county and watershed boundary polygons provided by the Maryland Department of Natural Resources. The Coastal Bays Watershed boundary, including DE and VA, was attained from the EPA - Basins dataset and is a generalized boundary. (2) Where necessary, the DISSOLVE command was also used to eliminate boundary lines between the original individual datasets in the final merged coverage.**This may have caused a change in the dataset through the loss of polygons or arcs originally in the individual datasets. Although we were diligent in preventing any loss of relevant data, we cannot make assurances that data was not lost.
7206 National Seashore Lane
Internal feature number.
Area of the features in square meters
Perimeter of features in meters
The wetland classification system is hierarchical, with wetlands and deepwater habitats divided among five major systems at the broadest level. The five systems include Marine (open ocean and associated coastline), Estuarine (salt marshes and brackish tidal water), Riverine (rivers, creeks, and streams), Lacustrine (lakes and deep ponds), and Palustrine (shallow ponds, marshes, swamps, sloughs). Systems are further subdivided into subsystems which reflect hydrologic conditions. Below the subsystem is the class which describes the appearance of the wetland in terms of vegetation or substrate. Each class is further subdivided into subclasses; vegetated subclasses are described in terms of life form and substrate subclasses in terms of composition. The classification system also includes modifiers to describe hydrology (water regime), soils, water chemistry (pH, salinity), and special modifiers relating to man's activities (e.g., impounded, partly drained). The NWI wetland code interpreter is an excellent tool for determining wetland classifications, available at - http://wetlandsfws.er.usgs.gov/NWI/webatx/atx.html. Simply enter the code found in the attribute NWI_Type (without any spaces) and click on 'Submit'.
Cowardin, L.M., V. Carter, F. Golet, and E. LaRoe. 1979. Classification of wetlands and deepwater habitats of the United States. U.S. Fish Wildlife Service. 103 pp.
Photo interpretation Conventions for the National Wetlands Inventory, March 1990
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For digital data orders on 3.5" floppy disk, a maximum order of 10 quads is allowed. Data may be ordered in latitude/longitude or State Plane Coordinate System coordinates (Universal Transverse Mercator coordinates are standard). Latitude/longitude coordinates are not available with GRASS format. For this service, the user must order data through USGS-ESIC for delivery on magnetic media. Please specify the desired coordinate specify wetlands overlay or wetlands overlayed with composite USGS base map.
9720 Executive Center Drive