Stratification of Virginia 2005

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Frequently-anticipated questions:


What does this data set describe?

Title: Stratification of Virginia 2005
Abstract:
The United States Department of Agriculture (USDA), National Agricultural Statistics Service (NASS) area sampling frame is a delineation of all parcels of land for the purpose of later sampling the parcels. The area frame is constructed by visually interpreting satellite imagery to divide a state into homogenous land use areas (strata) based on percent cultivated. The strata are typically defined as low, medium or high percent cultivated, non-agricultural land, urban use, agri-urban, or water. The boundaries of the strata usually follow identifiable features such as roads, railroads and waterways. The strata boundaries do not coincide with any political boundaries, with the exception of state boundaries.
Supplemental_Information: N/A
  1. How should this data set be cited?

    United States Department of Agr, National Agricultural Statistics Service, 2005, Stratification of Virginia 2005: U.S. Department of Agriculture, National Agricultural Statistics Service, Fairfax, Virginia.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -83.67
    East_Bounding_Coordinate: -75.24
    North_Bounding_Coordinate: 39.47
    South_Bounding_Coordinate: 36.54

  3. What does it look like?

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

    Calendar_Date: 2004
    Currentness_Reference:
    2004: Creation of original area sampling frame strata boundaries. 2005: Topology check performed (gaps and overlaps removed).

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

  6. How does the data set represent geographic features?

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

      Indirect_Spatial_Reference:
      U.S. Department of Commerce, 1988, Counties and Equivalent Entities of The United States, Its Possessions, and Associated Areas (Federal Information Processing Standard 6-4): Washington, D.C. National Institute of Standards and Technology.
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • G-Polygon (7506 (prior to dissolving boundaries))

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

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 17
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -81.00
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.00
      False_Northing: 0.0

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 30
      Ordinates (y-coordinates) are specified to the nearest 30
      Planar coordinates are specified in meters

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference 80.
      The semi-major axis of the ellipsoid used is 6378137.00.
      The flattening of the ellipsoid used is 1/298.257.

  7. How does the data set describe geographic features?

    Land Use Strata
    Homogeneous land use area based on percent cultivated (Source: U.S. Department of Agriculture, National Agricultural Statistics Service)

    Strata
    Land use category based on percent cultivated (Source: U.S. Department of Agriculture, National Agricultural Statistics Service)

    Value Definition
    13
     50% cultivated, (cultivated categories consist of land used for
    crops, the remaining portion of land in the cultivated strata may include pasture, woods, waste, rangeland, etc.)
    20 15%-50% cultivated, (cultivated categories consist of land used for crops, the remaining portion of land in the cultivated strata may include pasture, woods, waste, rangeland, etc.)
    31 Agri-urban with > 100 homes per square mile (less than 15% cultivated)
    32 Commercial/dense urban with > 100 homes per square mile (city center with 0% cultivated)
    40 < 15% cultivated, (cultivated categories consist of land used for crops, the remaining portion of land in the cultivated strata may include pasture, woods, waste, rangeland, etc.)
    50 Non-Agriculture
    62 Water

    Sum_Area
    The stratum area in square miles. (Source: U.S. Department of Agriculture, National Agricultural Statistics Service)

    Range of values
    Minimum: 232.001
    Maximum: 19157.471

    Sum_Acres
    The stratum area in acres. (Source: U.S. Department of Agriculture, National Agricultural Statistics Service)

    Range of values
    Minimum: 148482.236
    Maximum: 12260372.474

    Cnt_Strata
    Count of strata polygons in each strata prior to dissolving into a single feature. (Source: U.S. Department of Agriculture, National Agricultural Statistics Service)

    Range of values
    Minimum: 41
    Maximum: 2984


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?

    Area Frame Section staff

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

    Area Frame Section staff
    USDA/NASS/RDD/AFS
    3251 Old Lee Highway, Suite 305
    Fairfax, VA 22030

    703-877-8000 (voice)
    HQ_RD_OD@nass.usda.gov


Why was the data set created?

These data are intended for geographic display and analysis at the state level. The data should be displayed and analyzed at a scale of 1:100,000 or smaller (e.g., 1:250,000, etc.). The strata data are provided "as is". USDA/NASS does not warrant results you may obtain using the strata data.


How was the data set created?

  1. From what previous works were the data drawn?

    TopoDRG (source 1 of 4)
    Systems, Titan, 1995, SureMaps Raster: Titan Systems, San Diego, CA.

    Type_of_Source_Media: CD ROM
    Source_Scale_Denominator: 100000
    Source_Contribution: spatial and attribute information

    TM5imagery (source 2 of 4)
    Imaging, Space, 2002, Landsat 5 Thematic Mapper imagery: Space Imaging, Lanham, MD.

    Type_of_Source_Media: CD ROM
    Source_Contribution: spatial and attribute information

    Ag-Census (source 3 of 4)
    U.S. Dept. of Agriculture, National Agricultural Statistics Service, 2004, Census of Agriculture: U.S. Department of Agriculture, National Agricultural Statistics Service, Washington, D.C..

    Type_of_Source_Media: Paper
    Source_Contribution: spatial and attribute information

    JES (source 4 of 4)
    USDA, National Agricultural Statistics Service, 2004, June Enumerative Surveys.

    Type_of_Source_Media: paper
    Source_Contribution: spatial and attribute information

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

    Date: 2004 (process 1 of 2)
    The area sampling frame for Virginia was constructed in 2004 for use in 2005 and was based on SureMaps - USGS 1:100,000 TopoDRGs and Landsat5 imagery.

    Data sources used in this process:

    • TopoDRG
    • TM5imagery
    • Ag-Census
    • JES

    Date: 2005 (process 2 of 2)
    Individual county files were merged into a single state file and dissolved by strata. Topology was constructed in a personal geodatabase data format where overlaps and gaps were corrected. The data were exported to Environmental Systems Research Institute's Arcview shapefile format. Coordinates for the strata polygons are unprojected to geographic latitude and longitude (decimal degrees) referenced to the North American Datum of 1983 (NAD83).

  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?

  2. How accurate are the geographic locations?

    The sources used for digitizing strata boundaries are 1:100,000 scale Digital Raster Graphics

  3. How accurate are the heights or depths?

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

    There are no known gaps or missing data. This data set includes the area in square miles and number of acres for each strata. Because the area sampling frame strata boundaries are modified, the boundaries may not be coincident with strata boundaries of adjacent states.

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

    Checks for topological consistency were performed on this data set.


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:
None. Acknowledgment of the U.S. Department of Agriculture, National Agricultural Statistics Service would be appreciated in products derived from these data.

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

    USDA/NASS/RDD/GIB/AFS
    3251 Old Lee Highway, Suite 305
    Fairfax, VA 22030

    703-877-8000 (voice)

    Contact_Instructions: N/A
  2. What's the catalog number I need to order this data set?

  3. What legal disclaimers am I supposed to read?

    Users of the strata data are solely responsible for interpretations made from the product. The strata data are provided "as is". USDA/NASS does not warrant results you may obtain by using the strata data. Feel free to contact our staff at (HQ_RD_OD@nass.usda.gov) if technical questions arise in the use of the strata data.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 21-Jun-2005
Metadata author:
Lee Plowman
USDA/NASS/RDD/GIB/AFS
3251 Old Lee Highway, Suite 305
Fairfax, VA 22030

703-877-8000 (voice)
HQ_RD_OD@nass.usda.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)


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