Illinois Project T.O. 029

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Frequently-anticipated questions:

What does this data set describe?

Title: Illinois Project T.O. 029
A 1.5-foot resolution panchromatic (B and W) USGS Digital Orthophoto Quarter-quadrangle (DOQQ) A DOQQ is a raster image in which displacement in the image caused by sensor orientation and terrain relief has been removed. A DOQQ combines the image characteristics of a photograph with the geometric qualities of a map. The geographic extent of the DOQQ is equivalent to a quarter of a 7.5-minute map (3.75 minutes of latitude and longitude) with overedge . The overedge ranges from a minimum of 50 meters to 300 meters beyond the extremes of the primary and secondary corner ticks. DOQQs are produced with a 1-meter ground sample distance (GSD) and are cast on the Universal Transverse Mercator (UTM) projection on the North American Datum of 1983 (NAD83). Primary (solid) and secondary (dashed) corner ticks are burned into the image to indicate the geographic corners of the DOQQ. The primary ticks always show the NAD83 corners. The secondary ticks show either the NAD27 or the local horizontal datum in use in a specific area (e.g. the Puerto Rico datum, the Hawaiian datum). Each DOQQ is produced to meet a National Map Accuracy Standard (NMAS) for 1:12000 scale maps (10.16 meters radial error at a 90% probability). Each DOQQ is formatted with a variable length ASCII header followed by a series of 8- bit image data lines. The ASCII header is padded to equal the length of one image line. The header contains information on file organization, display (samples and lines), georeferencing, and production sources. The file structure for a native format DOQQ is analogous to a raw raster BIL (panchromatic) or BIP (RGB color). DOQQs are nominally produced from National Aerial Photography Program (NAPP) source imagery flown at 20,000 feet above average ground using a single source image for each DOQQ. NAPP imagery is flown leaf-off in deciduous vegetation regions.
  1. How should this data set be cited?

    Surdex Corporation and Science Applications International Corporation (SAIC), 2006, Illinois Project T.O. 029: U.S. Geological Survey, Sioux Falls, SD.

  2. What geographic area does the data set cover?

  3. What does it look like?

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

    Beginning_Date: 18-Feb-2005
    Ending_Date: 04-May-2005
    Currentness_Reference: Ground Condition

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

    Geospatial_Data_Presentation_Form: Remote-sensing 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, type Pixel

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

      Grid_Coordinate_System_Name: State Plane Coordinate System 1983
      SPCS_Zone_Identifier: 1202
      Scale_Factor_at_Central_Meridian: 0.999941176
      Longitude_of_Central_Meridian: -90.166666667
      Latitude_of_Projection_Origin: 36.66666667
      False_Easting: 700000
      False_Northing: 0.0

      Planar coordinates are encoded using Row and column
      Abscissae (x-coordinates) are specified to the nearest 1.5
      Ordinates (y-coordinates) are specified to the nearest 1.5
      Planar coordinates are specified in U.S. Survey Feet

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.5722210.

  7. How does the data set describe geographic features?

    Panchromatic orthoimagery is organized in a single channel. Each pixel is assigned a gray-scale value from 0-255 with 0 representing black and 255 representing white. Areas where data is incomplete due to lack of full image coverage are represented with the numeric value of 0 or 128.
    U.S. Department of the Interior, U.S. Geological Survey, 1996, Standards for Digital Orthophotos: Reston, VA.

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?

    Surdex Corporation and Science Application International Corporation (SAIC)

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

    Tim Bohn
    Surdex Corporation
    Project Manager
    520 Spirit of St. Louis Blvd.
    Chesterfield, MO 63005

    1-636-532-3427 (voice)
    1-636-537-9638 (FAX)

    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (EasternTime)
    The above is the contact information for Surdex in Chesterfield, MO

Why was the data set created?

This data depicts geographic features on the surface of the earth. DOQQs serve a variety of purposes, from interim base maps to field references for earth science investigations and analysis. The DOQQ is useful as a layer in a geographic information system (GIS) and as a tool for performing digital map revision. DOQQs form the medium-resolution image base for The National Map.

How was the data set created?

  1. From what previous works were the data drawn?

    PHOTO (source 1 of 3)
    Corporation, Surdex, 2005, NAPP.

    Type_of_Source_Media: Stable-base material
    Source_Scale_Denominator: 40000
    Stable-base aerial photography acquired at 1:40,000 scale using only metric aerial cameras with USGS calibration certificates. Provides the imagery for the digital orthoimage. Film is panchromatic.

    DEM (source 2 of 3)
    U.S. Geological Survey, 2003, USGS 1-arcsec NED.

    Type_of_Source_Media: Hard Drive
    USGS 1-arcsec National Elevation Dataset for the entire United States that was broken down into 1 degree cells.

    CONTROL (source 3 of 3)
    Corporation, Surdex, 2005, Project Photo Control.

    Type_of_Source_Media: CD-ROM
    Horizontal and vertical control used to establish positions and elevations for reference and correlation purposes and as input to the aerotriangulation process. Control consists of both Airborne GPS to provide camera station positions and photoidentifiable surveyed ground control for groundreference.

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

    Date: range 20051212 - 20060728 (process 1 of 1)
    Source imagery was collected using four cameras (two Wild RC-30 and two Jena LMK), all have 6" focal lengths and a current calibration by USGS. The imagery was processed by HAS Images Inc. in Dayton, OH. Airbone GPS data was processed by Surdex Corporation. Image negatives were scanned at 10-micrometer resolution on Leica DSW Image Scanners and dodge using SurDodge software by Surdex. The scanned images were then used as input, along with Airborne GPS data and camera calibration data in Intergraph's ImageStation Automatic Triangulation (ISAT) for point mensuration. An assessment of the USGS National Elevation Dataset (NED) revealed several areas of insufficient data, at which other DEM sources obtained by Surdex was used. The aero triangulation parameter data, used with the scanned and dodged imagery were orthorectified using the modified elevation models and Surdex orthorectification software. Some orthorectified images were then mosaicked, if necessary, to reduce minor image defects. Radiometric balancing achieved using Inpho's OrthoVista, as necessary, to produce a consistent image tone for DOQQs. Product tiles were then extracted and converted to GeoTIFF format written to hard drive for delivery.

  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?

    The digital dodging software developed by Surdex is used to counter the effects of haze and sun angle illumination on the film photography. This procedure has been proven to provide a distinct advantage in minimizing the need for extensive radiometric balancing and improves automatic pass/tie point collection during the aerotriangulation phase. The net affect of this program is to drive the source image closer to a histogram with a nearly Gaussian distribution. The output of this program will always produce an image with full dynamic range, nearly regardless of the source image. Minimal radiometric balancing was achieved using Inpho's Ortho Vista software.

  2. How accurate are the geographic locations?

    Random selection of 5% of the DOQQ tiles for excessive edge match offset.

  3. How accurate are the heights or depths?

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

    DOQQ images are visually inspected for completeness to ensure that no gaps or image misplacements exist within the 3.75-minute image area or the overedge coverage. DOQQs can be derived by mosaicking multiple images to ensure complete coverage. and between adjacent images. DOQQs are nominally produced from National Aerial Photography Program (NAPP) source imagery flown at 20,000 feet above average ground using a single source image for each DOQQ. NAPP imagery is flown leaf-off in deciduous vegetation regions. Source imagery is nominally cloud free. Coastal areas and international boundary regions may have areas without images (void areas) in parts of the coverage. These void areas have a radiometric value of either zero (black) or 128 (uniform gray). DOQQs nominally are produced with overedge coverage. This coverage is variable and may range from a minimum of 50 meters to a maximum of 300 meters beyond the extremes of the primary or secondary corners. The resulting DOQQ is a rectangle whose size may vary in relation to adjoining DOQQs.

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

    All DOQQ header data and image file sizes are validated using USGS software before being archived. This validation process ensures correct physical format and field values for header elements. Logical relationships between header elements are tested. Overlap regions between individual DOQQs are visually inspected for excessive horizontal displacement.

How can someone get a copy of the data set?

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

Access_Constraints: None
None. However, users should be aware that temporal changes may have occurred since this data set was collected and that some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of it's limitations. Acknowledgment of the U.S. Geological Survey would be appreciated for products derived from these data.

Who wrote the metadata?

Last modified: 22-Jun-2006
Metadata author:
John Zuzek
Science Applications International Corporation (SAIC)
Site Manager - SAIC Melbourne Office
100 Rialto Place, Suite 200
Melbourne, FL 32901

1-321-751-3235 (voice)
1-321-757-7870 (FAX)

Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (EasternTime)
Contact_Instructions: The above is the contact information for SAIC in Melbourne, FL
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

Illinois Natural Resources Geospatial Data Clearinghouse

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