Snake/Salt River Basin Plan - Huc 4 Boundaries

Metadata also available as

Frequently-anticipated questions:

What does this data set describe?
    Title: Snake/Salt River Basin Plan - Huc 4 Boundaries
    Abstract:
    The Geographic Information Retrieval and Analysis System (GIRAS) was developed in the mid 70s to put into digital form a number of data layers which were of interest to the USGS. One of these data layers was the Hydrologic Units. The map is based on the Hydrologic Unit Maps published by the U.S. Geological Survey Office of Water Data Coordination, together with the list descriptions and name of region, subregion, accounting units, and cataloging unit. The hydrologic units are encoded with an eight- digit number that indicates the hydrologic region (first two digits), hydrologic subregion (second two digits), accounting unit (third two digits), and cataloging unit (fourth two digits). The data produced by GIRAS was originally collected at a scale of 1:250,000. This data set is a modification for Wyoming of the original United States HUC data produced by the USGS. The primary modifications made in this data set by the Wyoming Water Resources Center include 1) removal of hydrologic units that do not drain within Wyoming and 2) modification of the hydrologic unit boundaries to better encompass streams and lakes represented in the 1:100,000 scale Digital Line Graph (DLG) of surficial hydrography. This metadata has also been altered from original USGS metadata to be more specific for Wyoming.

  1. How should this data set be cited?

    Steeves, Peter and Douglas Nebert; modified by, 19948, Snake/Salt River Basin Plan - Huc 4 Boundaries: U.S. Geological Survey; University of Wyoming WyGISC, Reston, Virginia; Laramie, Wyoming.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -111.049393
    East_Bounding_Coordinate: -109.763805
    North_Bounding_Coordinate: 44.490697
    South_Bounding_Coordinate: 42.484622

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: 1994
    Currentness_Reference: publication date

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • G-polygon (34)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000000. Longitudes are given to the nearest 0.000000. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.400000.
      The flattening of the ellipsoid used is 1/294.978698.

  7. How does the data set describe geographic features?

    huc250_ssdd27

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    AREA

    PERIMETER

    HUC250_

    HUC250_ID

    HUC

    REG_NAME

    SUB_NAME

    ACC_NAME

    CAT_NAME

    ACRES

    Entity_and_Attribute_Overview:
    For definition of drainage basins, there are two principal tabular data elements of interest. The first, "HUC", stands for the Hydrologic Unit Code and includes the 8-digit cataloging unit as assigned to the basin polygon by the U.S. Geological Survey. The original dataset also contained an attribute, "SOURCE", an attribute of each bounding line segment (arc), incorporating a code to define the source and scale of the source linework. However, in the modifications made specifically to Wyoming, these arc attributes were lost. Reference should be made to the original HUC data available from USGS for this information. Names for regional units, subregion units, accounting units and cataloging units were added for each of the polygons encompassing Wyoming, as well as the acreage associated with each unit. These attributes are called REG_NAME, SUB_NAME, ACC_NAME, CAT_NAME and ACRES, respectively.
    Entity_and_Attribute_Detail_Citation: Not Available

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    USGS Water Resources Division; Tom Kohley, U. of Wyoming

  3. To whom should users address questions about the data?

    U.S. Geological Survey, Water Resources Div. (WRD)
    c/o Mark Negri
    Computer Specialist, Spatial Data Support Unit
    12201 Sunrise Valley Drive, MS-445
    Reston, VA 20191
    USA

    703-648-5613 (voice)
    703-648-5295 (FAX)
    mnegri@usgs.gov

    Hours_of_Service: 6:30am-3:30pm EST
    Contact_Instructions: May contact thru email or telephone

Why was the data set created?
The HUC dataset was compiled originally to provide the National Water Quality Assessment (NAWQA) study units with an intermediate- scale river basin boundary for extracting other GIS data layers. The data can also be used for illustration purposes at intermediate or small scales (1:250,000 to 1:2 million). This modified dataset was produced under contract with the Wyoming Game and Fish Department for the purpose of wildlife habitat prioritization in Wyoming.

How was the data set created?
  1. From what previous works were the data drawn?

    GIRAS (source 1 of 1)
    Survey, US Geological , unknown, GIRAS.

    Type_of_Source_Media: digital
    Source_Scale_Denominator: 250000
    Source_Contribution: main source

  2. How were the data generated, processed, and modified?

    Date: 1995 (process 1 of 5)
    Procedures described in this section pertain to conterminous US data: The data was recieived as compressed giras tar files representing either a 1:250,000-scale (1:250K) quadrangle or a 1:100,000-scale (1:100K) quadrangle. Each file was named after its respective quadrangle. A coverage of 1:250k quadrangles was used to divide the country up into four sections and get a list of names for each section. Using GIRASARC2, an aml designed to create an ARC/INFO data-set (coverage) from a GIRAS file and a corresponding neat line coverage. After the files for a given section were all converted into ARC/INFO format, the outer edge (original neatline) was selected and deleted and the mathematically-calculated neatline coverage from the GIRASNEAT AML program was copied in. The original neatline was replaced with a calculated neatline because in all cases, the outline of the coverage quad never quite conformed to a "true" neatline causing overlaps and gaps between adjacent maps. The new neatline was connected to the internal arcs where they intersected. Lines which did not quite join the new neatline were extended to the edge with a maximum tolerance of 500 meters. All extensions were made within this tolerance. All arcs which extended beyond the new neatline were clipped off. All coverages were checked for additional dangles and then a MAPJOIN was run using NET as the feature option. Finally, most map edgelines were removed from the MAPJOINed coverage to create a seamless basin coverage with polygons (basins) and arcs (boundaries) with attributes. Errors found in the HUC250 coverage published as OFR 94-0326. Citation U.S. Geological Survey, 1990. Land Use and Land Cover Digital Data from 1:250,000- and 1:100,000-Scale Maps. Data Users Guide 4, 33 pp, Reston Virginia.

    NOTE - this shapefile was clipped to the Snake/Salt Basin Boundary and reprojected as part of the Wyoming Water Plan.

    Date: 1996 (process 2 of 5)
    Modifications made by the Wyoming Water Resources Center (WWRC): The WWRC modified the original Hydrologic Unit database by first removing all units that did not drain within the state of Wyoming. For the # remaining units in the state, the boundaries of each unit were modified to better represent the actual drainage area. The hydrologic units for Wyoming were compiled at a scale of 1:250,000 and are often overlaid with the 1:100,000 scale surficial hydrography DLG to produce maps of basin wide hydrography. The overlay of these two layers within the GIS often identified areas where a stream or lake intersected the boundary of the hydrologic unit due (most likely) to the difference in map scale between the two GIS layers To remove the intersections between hydrologic unit boundaries and streams/lakes in the hydrography DLG, we first assumed that the 1:100,000 scale DLG information was more spatially accurate than the 1:250,000 scale hydrologic unit boundaries. Using this assumption, we modified only the hydrologic unit boundaries in ArcEdit using the hydrography DLG as a background coverage for reference. Elevation (e.g. DEM) was not used as a reference coverage. Changes made to the unit boundaries consisted mostly of boundary extensions in order encompass streams that were in the upper portions of each basin. No new boundaries were added and none were removed.

    (process 3 of 5)
    Metadata imported.

    Data sources used in this process:

    • C:\DOCUME~1\decook\LOCALS~1\Temp\xml6.tmp

    (process 4 of 5)
    Metadata imported.

    Data sources used in this process:

    • C:\DOCUME~1\decook\LOCALS~1\Temp\xml42.tmp

    (process 5 of 5)
    Metadata imported.

    Data sources used in this process:

    • C:\DOCUME~1\decook\LOCALS~1\Temp\xml5F.tmp

  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?

    Label point accuracy was checked by making a point cover of polygon labels from the 1:2,000,000 HUC coverage and then doing an identify of those points in the 1:250,000 scale HUC polygon. This procedure looked for both new or missing polygons, and was also used to check attribute values. Both coverages were also dissolved by accounting unit and comparisons made of the number and location of remaining polygons and corrections made.

  2. How accurate are the geographic locations?

    The line work for the HUC coverage was checked against the line work from: (1) the 1:2,000,000 HUC coverage by plotting both data sets out on one large graphic (about 1:3,000,000). No major discrepancies were found except in coastal areas where the 1:2,000,000 scale coverage had more detail than the 1:250,000 scale coverage. (2) line work from 1:24,000 scale digitized drainage basins in Colorado, Illinois, and New Jersey. The match was generally good with departures generally less than 2500 meters. The biggest departures were in Colorado and were as large as 4000 meters. (3) line work from the 1:2,000,000 scale rivers coverage for the USA by plotting both data sets out on one large graphic (about 1:3,000,000). In general the nesting of streams in HUCs was good and HUC boundaries intersected steams at stream intersections. (4) line work from 1:100,000 scale streams from Colorado, Illinois, and Kansas. The nesting of streams in HUCs was very good. Stream arcs for the most part did not cross HUC arcs except at stream intersections. The error (distance from intersection to HUC line) between HUC lines and stream intersection was less than 500 meters at all intersections checked (about 25).

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    complete to USGS level four hydrologic unit code

  5. How consistent are the relationships among the observations, including topology?

    Polygon and chain-node topology present.

How can someone get a copy of the data set?
Are there legal restrictions on access or use of the data?

Access_Constraints: none
Use_Constraints:
These data were digitized at a scale of 1:250,000 and use of these boundaries with larger scale data (i.e. 1:24k hydrography) is not recommended as it would be beyond the resolution capabilities of the data set. Although the boundaries of the hydrologic units were modified to best match the 1:100,000 scale surficial hydrography DLG, these data should not be considered a 1:100,000 scale product.

  1. Who distributes the data set? (Distributor 1 of 1)

    WyGISC
    c/o Data Manager
    Box 4008 University Station
    Laramie, Wyoming 82071
    USA

    307-766-2735 (voice)
    n/a

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    The distributor shall not be held liable for improper or incorrect use of this data, based on the description of appropriate/inappropriate used described in this metadata document.

  4. How can I download or order the data?

Who wrote the metadata?
Dates:
Last modified: 17-May-2004

Metadata author:
WyGISC
c/o Margo Berendsen
Box 4008 University Station
Laramie, Wyoming 82071
USA

307-766-2735 (voice)
meh@uwyo.edu

Contact_Instructions: <http://www.sdvc.uwyo.edu/>
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Metadata extensions used:

Generated by mp version 2.7.33 on Mon May 17 16:48:21 2004