IDXPTRMBR - Township Tiling Index for King County Raster Data

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Frequently-anticipated questions:

What does this data set describe?

Title: IDXPTRMBR - Township Tiling Index for King County Raster Data
A spatial tiling index designed for storage of file-based image and other raster (i.e., LiDAR elevation, landcover) data sets. An irregular grid of overlapping polygons, each enclosing its respective Public Land Survey System (PLSS) township in an orthogonal polygon minimally encompassing all portions of that township, i.e., minimum bounding rectangle. The amount of overlap between adjacent tiles varies depending on the geometry of the underlying township. Currently extended to include all townships within or partially within King County as well as those townships in the southwestern portion of Snohomish County included within King County's ESA/SAO project area. The name of the spatial index is derived from the acronym (I)n(D)e(X) (P)olygons for (T)ownship-(R)ange, (M)inimum (B)ounding (R)ectangle, or idxptrmbr. Tile label is the t(township number)r(range number)as in t24r02. The meridian zone identifiers, N for townships and E for range is inferred as this index is intended as a local index for ease of use by the majority of users of GIS data. Lowercase identifiers are used for consistency between Unix and Windows OS storage. This index or tile level is the primary user-access level for most LiDAR elevation, orthoimagery and high-resolution raster landcover data. However, not all image and raster data is stored at the tiling level if a given data's resolution does not justify storing the data as multiple tiles.
This spatial index is one of three index or tiling levels used to store King County image and raster data. The index level lower than this is the idxp7500 index. The index level immediately higher than this is idxpzone. Each higher index level is designed to build upon the lower levels, with the same data often stored at more than one level (though at different resolutions) to meet a range of business and software requirements. Individual shapefiles for each of the cells in this index are available in gisimage/images/reference/indexes/idxptrmbr_shp as 'tileabb'mbr.shp.
  1. How should this data set be cited?

    County, King, 20030701, IDXPTRMBR - Township Tiling Index for King County Raster Data: King County, King County, WA.

    Online Links:

    Other_Citation_Details: None

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -122.653761
    East_Bounding_Coordinate: -120.922772
    North_Bounding_Coordinate: 48.054413
    South_Bounding_Coordinate: 46.977576

  3. What does it look like?

    <> (JPG)
    JPG File of layer overlain on base of WA counties or local cities

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

    Calendar_Date: 01-Jul-2003
    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?

      The PSLC project area in combination with the King County ESA/SAO Project area comprise the entirety of King County and southwestern Snohomish County (WRIA 8). The PSLC portion encompasses approximately 500 square miles, including Vashon Island, the Seattle urban environs, and mid-central King County. The ESA/SAO portion, approximately 1800 square miles, includes the remainder of King County and the Snohomish portion.
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • GT-polygon composed of chains (0)

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

      The map projection used is NAD 1983 HARN StatePlane Washington North FIPS 4601 Feet.

      Projection parameters:
      Standard_Parallel: 47.5
      Standard_Parallel: 48.73333333333333
      Longitude_of_Central_Meridian: -120.8333333333333
      Latitude_of_Projection_Origin: 47.0
      False_Easting: 1640416.666666667
      False_Northing: 0.0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.00025
      Ordinates (y-coordinates) are specified to the nearest 0.00025
      Planar coordinates are specified in foot_us

      The horizontal datum used is D North American 1983 HARN.
      The ellipsoid used is GRS 1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.

  7. How does the data set describe geographic features?

    Polygon attribute table (Source: ESRI)

    Feature Geometry (Source: ESRI)

    Coordinates defining the features

    Unique integer identifier for each tile composed the township number cocantenated with the range number, i.e. the identifier for township 22, range 12 would be 2212, the identifier for township 22, range 03 would be 2203. (Source: King County)

    Unique integer comprised of two-digit township integer cocantenated with two-digit (left-padded with zero where necessary) range number.

    Internal feature number. (Source: ESRI)

    Range of values

    Sequential unique whole numbers that are automatically generated.

    Unique alphanumeric identifier for each cell comprised of township number prefaced with 'T' cocantenated with range number (left-padded with zero, where necessary) prefaced with a 'R'. (Source: King County)

    Unique integer comprised of two-digit township integer cocantenated with two-digit (left-padded with zero where necessary) range number.

    Same alphanumeric township-range identifier found in mbr_abb item but with lowercase t and r, indicating township and range, respectively. (Source: King County)

    Unique alphanumeric code

    Two-character alpha code for township number. (Source: King County)

    Alpha expression of township number

    Two-character alpha code for township number. (Source: King County)

    Alpha expression of Range number. Left-padded with zero where necessary.

    Minimum State Plane easting value for tile bound. (Source: King County)

    Range of values

    Minimum State Plane northing value for tile bound. (Source: King County)

    Range of values

    Maximum State Plane easting value for tile bound. (Source: King County)

    Range of values

    Maximum State Plane northing value for tile bound. (Source: King County)

    Range of values

    Area of polygon (Source: ESRI)

    System-generated area

    Perimeter of polygon (Source: ESRI)

    System-generated perimeter

    All tiles are identified with a several attributes that indicate the tile-id, its bounding coordinates and the township-range represented. As the shapefile serves primarily as a spatial index,the mbr_abb and mbr_abblc are the primary attributes needed to correctly reference and describe the location of the cell tile.
    Entity_and_Attribute_Detail_Citation: None

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?

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

    King County GIS Center
    c/o Victor High
    Senior GIS Specialist
    201 S Jackson St, Suite 706
    Seattle, WA 98104

    206-263-4845 (voice)

Why was the data set created?

This index is the primary User Access level for image/raster datasets. It provides multiple file-based data sets to be accessed at full or near full resolution in a common, consistent tile and naming scheme. The index also serves as a useful central reference scheme for identification of real-world locations as it references the commonly used township-range grid of the PLSS. As each cell is defined with orthogonal edges relative the Washington State Plane coordinate system, and is defined by easting and northing bounds rounded to the nearest 100 foot, it accomodates most common pixel resolutions of multiple Ground Sample Distance without partial pixel effects and without zero or NULL data 'splinters'.

How was the data set created?

  1. From what previous works were the data drawn?

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

    Date: 01-Mar-2002 (process 1 of 5)
    Heads up digitizing was used to create minimum-bounding rectangles around each township in the project area. This portion included the subjective interpretation of the amount of buffer to include in each tile. This was performed in a CAD-based software package called VROne

    Date: 01-May-2002 (process 2 of 5)
    The minimum and maximum bounds were captured in a Microsoft Excel spreadsheet where the bounds were rounded to the next highest 100 foot easting and northing increment.

    Date: 01-Feb-2003 (process 3 of 5)
    The spreadsheet was converted to a text file which was used in an ArcInfo AML to create individual shapefile polygons for each township tile. The shapefiles were merged in ArcView to a composite shapefile. Final attributes, including min and max bounds and identifiers were appended from a text file converted to a dbf.

    Date: 01-Jun-2003 (process 4 of 5)
    Some of the township tile bounds along the edges of the King County were not described to the true extent of the township but rather to the extent of the data available from the data projects. To standardize the extents of all tiles and to ensure that subsequent tiles could be appended, any partial townships were regenerated. The Excel spreadsheet was updated to reflect the new bounds, new tiles generated and the composite index shapefile was updated.

    Date: 01-Mar-2010 (process 5 of 5)
    To accomodate the larger extents of newer imagery acquisition projects, additional township tiles were appended to all edges of the grid, resulting in a final grid that covers all directions equally.

  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?

    Identifiers for each cell are unique and reference the underlying township/range that encompasses.

  2. How accurate are the geographic locations?

    The bounds of each cell were generated from State Plane easting and northing coordinate values defined by a minimum bounding rectangle interpretation of the township extent. Overlap with adjacent tiles was provided to ensure sufficient data buffers. The interpreted bounds were rounded up the next nearest 100 foot easting and northing value.

  3. How accurate are the heights or depths?

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

    The index currently covers the King County and southwestern Snohomish County areas currently involved in several related image/raster data acquisition projects. The extent has been buffered to encompass some adjoining areas. Those tiles at the edge of the current data project area are defined to their full township extent to allow appending subsequent townships if necessary.

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

    All cells have a label attribute. The half-townships in eastern King County are included in the tile of full township of the same name, i.e., t24.5sr11e is included in the t24r11 tile.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
King County data are made available with the understanding that they shall be used exclusively by the obtainer or his/her authorized agents. Digital products may not be reproduced or redistributed in any form or by any means without the express written authorization of King County.

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

    KCGIS Center
    c/o Cheryl Wilder
    Data Sales Coordinator
    201 S Jackson St, Suite 700
    Seattle, WA 98104

    206-263-5220 (voice)

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


  3. What legal disclaimers am I supposed to read?

    King County disclaims any warranty of use of any digital product or data beyond that for which it was designed.

  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 19-Dec-2012
Metadata author:
King County GIS Center
c/o Mike Leathers
GIS Data Coordinator
201 S Jackson St, Suite 706
Seattle, WA 98104

206-263-4867 (voice)

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

Generated by mp version 2.8.24 on Sun Feb 18 16:02:25 2024