The files names are 8dot3 compliant. In most cases, first five characters of the file correspond to the file names designated by USGS. The Comma-Separated-Value database file, doqqdb.csv, see below for link, lists these five-letter abbreviations (as used by MD DNR) for USGS quadrangle names. Sixth character indicates ordinal_direction of the quadrant, and is as follows:
1-NE quadrant; 2-SE quadrant; 3-SW quadrant; 4-NW quadrant.
For each quarter quadrant linear features and polygonal features have to exported separately from the native software - MicroImages of Lincoln, Nebraska's TNTMIPS. TNTMIPS uses a proprietary format, known as ".RVC" for vector file structure. Seventh character of the file name indicates whether the file is for a linear (l) or polygonal (p) feature. Both, linear and polygonal files must be displayed together to realize the complete extents of the wetlands present in a given area. Eighth character is always a 6, indicating that the vector is a DNR_Wetland vector. Based on this Beltsville Quad has a total of eight main files - two each for each quadrant. These are as follows:
Belts1l6 - Beltsville NE linear; Belts1p6 - Beltsville NE polygon; Belts2l6 - Beltsville SE linear; Belts2p6 - Beltsville SE polygon; Belts3l6 - Beltsville SW linear; Belts3p6 - Beltsville SW polygon; Belts4l6 - Beltsville NW linear; Belts4p6 - Beltsville NW polygon.
This is the convention followed for all files.
The following is an important link related to this dataset/metadata.
<http://dnrweb.dnr.state.md.us/gis/data/index.html> This page has a link to DataDownload. Select either 'Wetlands Inventory - DNR (1:12,000, 1988-1995) Data' or 'Digital Orthophoto Quarter Quad (DOQ) - Color Infrared, 1:12,000, 4 meter resolution Data' from the drop down list; on the right side on this download page. Downlaod the wetlands data for any of the counties, or a quarter quad if the DOQ data is selected from the drop down list. This downloads a zip file. This downloaded zip file, along with the wetlands vectors (or the DOQ), contains the Photo Database in a comma separated file, named 'DOQQdb.csv.' This file contians the five character abbreviation and the date of photo flown for creating the Dgital Orthophoto Quarter Quads and the wetlands vectors. Additionally, see the file(s) doqqdb.htm and/or doqqdb.txt for the Photo Database metadata; contained in the downloaded zip file.
The attributes must be within a valid set of codes as defined by Cowardian 1987 manual. (Cowardin, L.M., V. Carter, F. Golet, and E. LaRoe. 1979. classification of wetlands and deep water habitats of the United States. U.S. Fish Wildlife Service. 103 pp.) For any given wetland file, this is done by exporting the linear and polygon wetlands attributes database to a text file. This text file is then passed on as a parameter to a batch program 'ATX.exe' obtained from Nontidal Wetlands Inventory office of the U. S. Fish and Wildlife Service. The output of this process is another text file which is evaluated for flagged 'bad' attributes. These are noted and EarthData International is informed of this for fixing. Refer to the 'Process Step' for further details.
Files contain ground planimetric coordinates and wetland attributes. The quadrangles were originally referenced to the Maryland State Plane Coordinate System Zone 1900 in the North American Datum of 1983 (NAD83) horizontal datum using the Geodetic Reference System 1980. The scanning process captures the data at a scanning resolution of at least 0.001 inches; the resulting raster data are vectorized, hand fitted by photo interpreters to the digital image and then attributed on an interactive editing station. Quality control steps occur throughout the photo interpretation, map compilation, and map reproduction processes at EarthData International.
1. Spatial positioning: This is a visual inspection of fit over digital orthophoto quarter quad (DOQQ). Each wetland vector is overlayed on the DOQQ and hundred percent of the linear and polygon features are checked.
2.Attribute and label accuracy: one hudred percent of the linears and polygons must be attributed. The labels are checked against the attributes of the vector and must match the attributes.
The attributes must be within a valid set of codes as defined by Cowardian 1987 manual. (Cowardin, L.M., V. Carter, F. Golet, and E. LaRoe. 1979. classification of wetlands and deep water habitats of the United States. U.S. Fish Wildlife Service. 103 pp.) For any given wetland file, this is done by exporting the linear and polygon wetlands attributes database to a text file. This text file is then passed on as a parameter to a batch program ATX.exe obtained from Nontidal Wetlands Inventory office of the U. S. Fish and Wildlife Service. The output of this process is another text file which is evaluated for flagged bad attributes. These are noted and EarthData International is informed of this for fixing.
At this point take note of these important URLs. U. S. Fish and Wildlife Service located at the URL <http://www.nwi.fws.gov/downloads.htm> At this URL pick the link for 'View NWI Map Codes and Definition' which will take you to the URL: <http://www.nwi.fws.gov/atx/atx.html> Here you can input the wetland classification code in question. The program used to run this is atx.exe. The result of your inquiry would be whether the questionable classification is from a valid NWI codeset. You also have a choice of short, long or none for the description of a valid NWI code; this makes for a good reading and provides for the understanding of wetlands. This also has a link for the code_legend. This lays out a schematic of the hierarchial classification system. Detailed explanation of this system is given in Entity_Definition_Source section of this metadata.
3. Edge Match: All linears and polygons must match across adajcent map sheets. The polygons are closed off at the map boundary/neat line, whereas the linears are not. The current standards for linears is that these stop at about 50 feet from the edge of the neat line. This standard was adopted since 1999.
4. Topological Check: The wetland vectors are checked for overshoots, unclosed polygons, missing or multiple attribution. These are done by queris developed at MD DNR using the query builder of TNT MIPS software.
A secondary QC is also performed on a randomly selected number of map sheets in each production batch.. This is done on couple of the quadrangles that were picked to do the primary QC. Additional quarter quads are also selected for this secondary QC. This is still in the .rvc format.
The files are delivered and QC done in TNTMIPS .rvc format. The files are then exported to the ESRI Shape file format. A primay and secondary QC is done on these shape files as well. This is to make sure that files have been named correctly and that they are spatially correct. Checks are also done to make sure that the attributes did not get mixed up or left out during the export process. The extents of the vectors are also checked to make sure that a given qurter quad covers the full extent of the quadrangle grid.
Any problems found are noted and reported to EarthData International. EarthData International fixes these and sends the files to MD DNR which are checked again for any problems that might have been introduced during the fixes.
This quality control is done using TNT MIPS software , and on Arc View version 3.1 and higher.
1) at least periodically, the land supports predominantly hydrophytes; 2) the substrate is predominantly undrained hydric soil; and 3) the substrate is non-soil and is saturated with water or covered by shallow water at some time during the growing season of each year.
Explanations of Wetlands classification system: NWI classification hierarchy is based on wetlands hydrology, substrates, and vegetation:
System; SubSystem; Class; and SubClass
The initial defining category, System, is composed of hydrogeomorphic wetland classes which are based on geomorphic setting, water source, and hydrodynamics. (Riverine, Palustrine, Estuarine, ...)
Next in hierarchy is Subsystem, which is a measure of length of time that wetland is inundated with water. (Perennial, Intermittent, Tidal, ...)
Class is the third subcategory in classification system which is related to the substrate present in the wetland. If there is no vegetation present, it simply gives the substrate present. When vegetation does occur, it describes extent and location of vegetative cover. (Streambed, Rockbottom, AquaticBed, ...)
Finally, Subclass describes types of substrate and/or vegetation that occur in the wetland. (Bedrock, Mud, Algal, RootedVascular,...)
In addition to this classification system, NWI uses four groups of Modifiers to further delineate wetlands when appropriate:
Water Regime further describes source of water and inundation frequency of wetland.
Water Chemistry describes pH and salinity of water.
Soil is a description of soil taxonomy based on criteria from U.S. Soil Conservation Service, Soil Survey Staff 1975:13-14, 65.
Origin of Altered Wetlands are special modifiers describing artificially created or modified wetlands. ( farmed, diked, beaver, partially drained, ...). are determined primarily by ebb and flow of oceanic tides.
NWI identifies 5 different ecological systems which contain multiple and varying coding for subsystems, class, subclass and modifiers including water regimes, water chemistry, soils and special modifiers.
The NWI codes found in the attribute table of this database are a concatenation of coding for ecological systems, subsystems, class, subclass, and modifying terms for water regime, chemistry and soil. For example, marine, subtidal, open water body would be coded M1OW; whereas a marshy area of persistent emergent vegetation would be coded PEM1. These codings can be found in the USFWS; whereas individual codes can be found in subsequent items.
ITEM DEFINITIONS:
SYSTEM: Ecological Systems (M,E,R,L,P)
M = marine systems Marine system consists of the open ocean overlying the continental shelf and its associated high-energy coastline. Marine habitats are exposed to the waves and currents of the open ocean and the water regimes are determined primarily by the ebb and flow of oceanic tides.
E = Estuarine systems Estuarine system consists of deep water tidal habitats and adjacent tidal wetlands that are semi-enclosed by lands but have open, partially obstructed, or sporadic access to the open ocean, and in which open water is at least occasionally diluted by freshwater runoff from the land.
R = Riverine systems Riverine system incudes all wetlands and deep water habitats contained within a channel, with two exceptions:(1)wetlands dominated by trees, shrubs persistent emergents, emergent mosses, or lichens, and(2)habitats with water containing ocean-derived salts in excess of .5 parts per thousand.
L = Lacustrine systems Lacustrine system includes wetlands and deep water habitats with all of the following characteristics:(1)situated in a topographic depression or a dammed river channel:(2)lacking trees, shrubs, persistent emergents, emergent mosses, or lichens with greater than 30% areal coverage: and(3)total area exceeds 8 ha (20 acres).
P = Palustrine systems Palustrine system includes all nontidal wetlands dominated by trees, shrubs, persistent emergents, emergent mosses or lichens, and all such wetlands that occur in tidal areas where salinity due to ocean-derived salts is below 0.5 parts per thousand.
SUBSYSTEM: Ecological Subsystems: Marine, Riverine, Lacustrine, and Estuarine ecological systems have subsystem with varying codes while palustrine systems do not.
Marine and Estuarine: 1 = subtidal, 2 = inter tidal
Riverine: 1 = tidal, 2 = lower perennial, 3 = upper perennial, 4 intermittent, 5 unknown perennial, (emergents found only in riverine tidal and riverine lower tidal subsytem.
Lacustrine: 1 = limnetic, 2 = littoral.
CLASS AND SUBCLASS
Subclass have repetitive coding according to class therefore an area of subclass 1 could be one of many types including bedrock, submergent coral et.
RB = rockbottom: 1 = bedrock, 2 = boulder,
UB = unconsolidated bottom: 1 = cobble/gravel, 2 = sand, 3 = mud, 4 = organic.
AB = Aquatic bed: 1 = submergent alga, 2 = submergent vascular, 3 = submergent moss, 4 = floating leaved, 5 = floating, 6 = unknown submergent, 7 = unknown floating.
FL = flat: 1 = cobble/gravel, 2 = sand, 3 =mud, 4 = organic, 5 = vegetated pioneer, 6 = vegetated non pioneer,
RS = rocky shore: 1 = bedrock, 2 = boulder, 6 = vegetated non pioneer.
BB = beach bar: 1 = cobble/gravel, 2 = sand.
EM = emergent: 1 = persistent, 2 = nonpersistent, 3 = narrow leaved nonpersistent, 4 = broad leaved nonpersistent, 5 = narrow leaved persistent, 6 = broad leaved persistent.
SS = scrub/shrub and FO = forested: 1 = broad leaved deciduos, 2 = needle-leaved deciduous, 3 = broad-leaved evergreen, 4 = needle-leaved evergreen, 5 = dead, 6 = deciduous, 7 = evergreen.
ML = moss/lichen: 1 = moss, 2 = lichen.
SB = stream bed: 1 = cobble/gravel, 2 = sand, 3 = mud, 4 = organic.
OW = open water.
WATER: Water Regimes: Non-tidal and Tidal;
Non-tidal: A = temporary, B = saturated, C = seasonal, D = seasonal well drained, E = seasonal saturated, F = semipermanent, G = intermittently exposed, H = permanent, J = intermittently flooded, K = artificial, Z = intermittently exposed permanent, W = intermittently flooded temporary, Y = Saturated/semipermanent/seasonal, U = unknown.
Tidal: K = artificial, L = subtidal, M = irregularly exposed, N = regular, P = irregular, R = seasonal tidal, S = temporary tidal, T = semipermanent tidal, V = permanent tidal, U = unknown.
WATER CHEMISTRY:
Coastal salinity: 1 = hyperhaline, 2 = eualine, 3 = mixohaline (brackish), 4 = polyhaline, 5 = mesohaline, 6 = oligohaline, 0 = fresh.
Inland salinity: 7 = hypersaline, 8 = eusaline, 9 = mixosaline, 0 = fresh.
pH modifiers for all fresh water: a = acid, t = circumneutral, l = alkiline.
MODIFIER: Soil: g = organic, n = mineral.
SPECIAL MODIFIERS: b = beaver, d = partially drained/ditched, f = farmed, h = diked/impounded, r = artificial, s = soil, x = excavated.
1) at least periodically, the land supports predominantly hydrophytes; 2) the substrate is predominantly undrained hydric soil; and 3) the substrate is non-soil and is saturated with water or covered by shallow water at some time during the growing season of each year.