King County 2002 Color Aerial Photography

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Frequently-anticipated questions:

What does this data set describe?

Title: King County 2002 Color Aerial Photography
Natural color orthophotography acquired in July 2002 covering approximately 2300 square miles of King County (including Vashon Island) and southwestern Snohomish County. Data was orthorectified using Lidar Digital Ground Model terrain information and tiled in a seamless mosaic. Default seamline matching was used. Original diapositive images were scanned at 11.5 microns yielding pre-orthophoto rectification raw pixal sizes of 0.77 feet for the 1"=1700' and 1.13 feet for the 1"=2500' data sets. Final output ground sample distance (gsd) is 1 feet for entire mosaic. Data is provided in MrSid compressed format at a 1:7 ratio. This lossy compression results in variable data quality and clarity. Orthorectified tiff files are available for this dataset. Larger zone and keyregion mosaics are also available, but at a higher compression, thus lower-resolution format.
The primary access to this data will be in a compressed MrSid format. Images are tiled to the King County idxptrmbr tile scheme - a tile scheme based on the PLSS township-range organization. See the KCGIS Spatial Data Catalog <> for more information on how King County imagery and other raster data is organized.
  1. How should this data set be cited?

    County, King, 200411, King County 2002 Color Aerial Photography: King County, King County, WA.

    Online Links:

    • None

    This imagery has been acquired as part of the ESA/SAO data acquisition project. The ESA/SAO project is a multi-department, multi-phase effort to update critical base resource and environmental data in GIS-compatible format. These related projects are operating under the umbrella of the Endangered Species Act/Sensitive Areas Ordinance (ESA/SAO) initiative.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -122.5470
    East_Bounding_Coordinate: -121.5785
    North_Bounding_Coordinate: 47.9279
    South_Bounding_Coordinate: 47.1305

  3. What does it look like?

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

    Beginning_Date: Jul-2002
    Ending_Date: Jul-2002
    Currentness_Reference: Acquisition date

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

    Geospatial_Data_Presentation_Form: Raster image

  6. How does the data set represent geographic features?

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

      This is a Raster data set. It contains the following raster data types:

      • Dimensions 4400 x 7400, type Pixel

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

      Grid_Coordinate_System_Name: State Plane Coordinate System
      SPCS_Zone_Identifier: Washington, North
      Standard_Parallel: 47.500000
      Standard_Parallel: 48.733333
      Longitude_of_Central_Meridian: -120.833333
      Latitude_of_Projection_Origin: 47.000000
      False_Easting: 1640416.666500
      False_Northing: 0.000000

      Planar coordinates are encoded using Row and column
      Planar coordinates are specified in Feet

      The horizontal datum used is North American Datum of 1983, 1991 correction.
      The ellipsoid used is GRS 80.
      The semi-major axis of the ellipsoid used is 20925604.4720406.
      The flattening of the ellipsoid used is 1/298.26.

  7. How does the data set describe geographic features?

    The images are stored in raster format. They have no attribute table.
    Entity_and_Attribute_Detail_Citation: Not applicable

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?

    Michael Leathers
    King County GIS Center
    GIS Data Coordinator
    201 S Jackson St
    Seattle, WA 98104

    206-263-4867 (voice)

Why was the data set created?

The 2002 King County orthorectified color imagery updates the King County Spatial Data Warehouse. Data is available for a range of internal and external GIS, engineering and other mapping applications. This data replaces Version 1 of the 2002 King County data which was stored in a lower-resolution format. The King County data provides full-county coverage.

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: Nov-2002 (process 1 of 4)
    Photos were acquired using standard film-based technology by Bergman and Associates under subcontract to 3di West. Photos were captured in stereo configuration. Aerial Triangulationwas performed utilizing airborne GPS and ground control to orient the photos to the Washington State Plane (North Zone) coordinate system.These low-level photos were collected at a photo scale of 1"=1700', and the high-level photos at 1" = 2500', with a 6" camera focal length.
    The film negatives were scanned at 11.5 microns by 3di, Easton, MD resulting in a pre-orthophoto rectified nominal pixel size of 0.77 feet for the low-level and 1.13 feet for the high-level. The digital images were output in Tiff-tiled format with separate planar configuration, with pyramid layers. The scanned images were delivered to King County for quality assessment on portable harddrives.

    Date: Dec-2002 (process 2 of 4)
    Digital terrain information was extracted from LiDAR rasters in ArcInfo Grid format captured in 2002. A composite grid based on 100 foot buffered idxp7500 index tiles that are resampled to 12 feet and converted to a point coverage using the GRIDPOINT command. ADDXY command was used to append coordinates to the attribute table. The PAT attribute table was unloaded to an ASCII file.
    The terrain information was not edited.

    Date: 2003 (process 3 of 4)
    Images and terrain information were input into the Ortho/Mosaic module in SOCET SET from Leica Geosystems and BAE. A list of all images required for the project area, as well as the name of the digital terrain file were provided to the software. The lower-left and upper-right coordinates of each idxp7500 Bounding Rectangle tile was provided and the program was executed.
    The ortho/mosaic seamline autogenerated by the software were not reviewed or edited. Bridges and overpasses/interchanges were not modeled during the orthorectification process. They are rectified to the ground per the LiDAR terrain model, as are all elevated/non-ground features.
    The orthophotos were not given a comprehensive quality evaluation.

    Date: 2004 (process 4 of 4)
    Output orthorectified idxp7500 tiles in TIFF format are clipped to the idxptrmbr boundary and compressed using MrSid format compression. The compression ratio is 1:7.

  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?

    Not applicable

  2. How accurate are the geographic locations?

    A thorough horizontal accuracy check has not been performed on the dataset.
    For the 1" = 1700' source photos: Maximum error, in areas of strong relief or over elevated features (i.e, overpasses), may be as great as 15 feet. Generally, error is expected to be less than this, in the range of 6-10 feet.
    For the 1" = 2500" source photos: Maximum error, in areas of strong relief or over elevated features (i.e, overpasses), may be as great as 20 feet. Generally, error is expected to be less than this, in the range of 10-15 feet.

  3. How accurate are the heights or depths?

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

    The dataset includes all images captured as part of the overflight. There were 793 photos collected for the 'western' (lowland) portion of the project area at a photo scale of 1" = 1700', covering an area of approximately 1500 sq. miles.
    For the 'eastern' (upland) portion of the project area 306 photos where taken at a photo scale of 1" = 2500', covering an area of approximately 825 sq. miles.
    Township tiles created from the 1" = 2500 foot photography are:
    Townships 19 Ranges 09-12, Townships 20 Ranges 09-12, Townships 21 Ranges 09-12 Townships 22 Ranges 10-11, Townships 23 Ranges 10-12, Townships 24 Ranges 10-14 Townships 25 Ranges 10-13, Townships 26 Ranges 10-13
    All other township tiles were created from the 1" = 1700' photography.
    The three half-townships in eastern King County are incorporated into their adjacent full townships, T24R11, T24R12, T24R13, per the tiling scheme.

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

    Variation in acquisition parameters, protracted acquisition schedule and water features result in less than optimal tonal balancing and overall color consistency. Adjustments to display characteristics in viewing software can enhance display quality.

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 digital data may not be reproduced or redistributed in any form or by any means without the express written authorization of the King County Department of Natural Resources and Parks/KCGIS Center.

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

    Dennis Higgins
    King County GIS Center, Client Services, Department of Natural Resources and Parks
    Manager, Client Services
    201 S Jasckson St, Suite 706
    Seattle, WA 98104

    206-263-4523 (voice)

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

    tXXrYY_02n100.sid, where tXX refers to the PLSS township on which the tile scheme is based and rYY indicates the range. _02 indicates the acquisition year is 2002, 'n' indicates natural color orthophotography, with '100' representing 100/100ths foot (= 1 ft) ground sample distance resolutions (gsd). Tiling levels at 7500, township-range and zone are all stored at 1 foot pixel resolution (with required compression). The KeyRegion full-county mosaic is provided as resampled 1.5 foot pixels. This resampling was required to accomodate maximum compression limits.

  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: Nov-2004
Metadata author:
Michael Leathers
King County GIS Center
GIS Data Coordinator
201 S Jackson St
Seattle, WA 98104

206-263-4867 (voice)

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

Generated by mp version 2.9.6 on Wed Apr 10 12:31:54 2013