Rivers and Streams

2M Rivers

Abstract: This data set is a line shape file representing surface water features (hydrography) in Wisconsin. The data are derived from the US Geological Surveys Digital Line Graphs (DLGs) at 1:2,000,000 scale. Feature representation (i.e., whether a river is represented by a line or a polygon) is determined primarily by how the corresponding entity is symbolized on the USGS source maps. Depending on the source map symbolization, portions of a river may be represented by either single-or double-line features, and other portions as polygons, such as when a river widens to form a lake.

Purpose Description: This data set provides a generalized representation of surface water (hydrography) in Wisconsin. The level of accuracy does not support detailed local analysis. The data are intended for use with ArcView, ARC/INFO, or other GIS software which support shapefile format data.

Access Constraints: None

Use Constraints: None

Currentness Reference: Publication of source USGS maps

Geographic Extent: Statewide

Native Data Environment: ArcView version 3.2

Maintenance Update Frequency: None Planned

Progress Type: Complete

Beginning Date: 1979

Ending Date: 1980

Process Step Description: Around 1991, WiDNR Geographic Services converted the 1:2,000,000-scale DLG files for the Great Lakes Region of the U.S. into single-precision ARC/INFO coverages using the ARC/INFO DLGARC command. The coverages were projected from UTM to WTM. Polygon topology was established with the CLEAN command using a fuzzy tolerance of less than 50.8 meters, the nominal resolution of the data. Line topology was established using the BUILD command with "line" option. Topological errors were corrected using ARCEDIT commands as needed to ensure topological integrity. A 10,000-meter buffer was created around the 1:2,000,000-scale Wisconsin state boundary. The buffered area was used to "tile" all layers in the DNR GIS database library ("WISLIB"). This tiling scheme provided for statewide coverage in a single tile as well as an overlap area of up to 10,000 meters into areas adjacent to Wisconsin. The principal modification to the DLG feature attribute coding design was the creation of separate items for thematically distinct feature groups. In general, thematically similar feature attributes were grouped together in the same items. The DLG major codes were dropped to avoid redundancy, but DLG minor codes were generally retained to accommodate users already familiar with the codes. New attributes of potential use were added to some coverages. An attribute identifying the largest polygon in multi-polygon units was added to some coverages to support statistical summaries and labelling. Following data verification, all coverages underwent spatial indexing (by use of the ARC/INFO INDEX command) to reduce data display times. Projection files were added to each coverage to enable users to display coverage projection parameters by entering the DESCRIBE command. All coverages were then inserted into the DNR GIS Database statewide library structure (WISLIB). In 1997, WISLIB data layers were projected from WTM based on NAD27 to WTM based on the 1991 adjustment to NAD83 (WTM83/91), and placed in the DNR GIS Database statewide library WISLIB91. The Hydrography (2M version) polygon shapefile was generated in 1998.

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100K Rivers

Abstract: The 1:100,000-scale Hydrography (HYDNW91C) data layer is derived from the 1:100,000-scale Digital Line Graphs (DLGs) of the U.S. Geological Survey (USGS). WiDNR enhancements to the source DLG data include conversion to ARC/INFO format, edgematching of internal DLG files, and restructuring of feature attribute codes.

Purpose Description: These data are used for display, mapping and analytic purposes where an intermediate-scale representation of hydrography is needed.

Access Constraints: None

Use Constraints: None

Currentness Reference: Publication dates of the source 1:100,000-scale USGS topographic maps

Geographic Extent: Statewide

Native Data Environment: ArcView version 3.2

Maintenance Update Frequency: None Planned

Progress Type: Complete

Beginning Date: 1979

Ending Date: 1989

Process Step Description: WDNR Geographic Services converted all 1:100,000-scale digital quadrangles with coverage in Wisconsin into single-precision ARC/INFO coverages using the ARC/INFO DLGARC command. The coverages were then projected from UTM to WTM with the PROJECT command. Polygon topology was established by means of the CLEAN command using a fuzzy tolerance of less than 2.54 meters, the nominal resolution of the data. Line and node topology was established using the BUILD command with 'line' and 'node' options, respectively. ARCEDIT commands were used, if needed, to correct topological errors and to ensure topological integrity. Various edgematching procedures were used to ensure topological fidelity along the ?seams? shared by adjacent coverages (these seams being artifacts of the DLG file structure). The principal modification to the DLG feature attribute coding design was the creation of separate items for thematically distinct feature attributes. Thematically similar feature attributes were grouped together in the same items. The DLG major codes were dropped to avoid redundancy, but DLG minor codes were generally retained to accommodate users already familiar with the codes. New attributes of potential use were added to some coverages. An attribute identifying the largest polygon in each political of administrative unit was added to some coverages, to facilitate statistical summaries or labelling. For each coverage in which DNR/GEO modified or added DLG feature attribute codes during processing, a code was added to a new item named EDIT_FLAG to indicate a code update had occurred. Following data verification, all coverages underwent spatial indexing (using the ARC/INFO command INDEX) to reduce display times. Projection (.prj) files were added to each coverage to enable users to display coverage projection parameters by entering the DESCRIBE command. All coverages were then inserted into the DNR GIS Database statewide library structure (WISLIB).

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24K Rivers

Abstract: This layer is an arc feature class of the 24K hydro ArcInfo coverage representing the hydrography (lakes and streams) of Wisconsin at 1:24,000 scale. All linear features in the layer including water features such as rivers, and the boundaries of those features, such as river and lake shorelines are represented. Other lines you may see in this layer are the connectivity and waterbody closure lines. This dataset is derived from U.S. Geological Survey (USGS) 7.5 minute quadrangle scanned separates (TIFF format); USGS Digital Line Graphs (DLGs); and (or) USFS Cartographic Feature Files (CFFs).

Purpose Description: These data are used for display, mapping and analytic purposes where a relatively detailed representation of hydrography is needed

Access Constraints: None

Use Constraints: None

Currentness Reference: Ground condition at publication date

Geographic Extent: Statewide

Native Data Environment: ArcGIS version 9.2

Maintenance Update Frequency: Every 6 months or as needed

Progress Type: Complete

Beginning Date: 1970

Ending Date: 2007

Process Step Description: Refer to "Wisconsin DNR 24K Hydrography Version 6 Database Design", accessible at: http://www.dnr.state.wi.us/maps/gis/documents/24khyd_db_design.pdf.

Refer to "Wisconsin DNR 24K Hydrography Data Capture and Feature-Coding Decision Rules", accessible at: http://www.dnr.state.wi.us/maps/gis/documents/24khyd_decision_rules.pdf.

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