Mosaic of Chicago Urban Area Color Aerial Photography, 2005

Metadata also available as - [Outline] - [Parseable text] - [XML]

Frequently-anticipated questions:


What does this data set describe?

Title: Mosaic of Chicago Urban Area Color Aerial Photography, 2005
Abstract:
This data set is an ArcSDE raster mosaic of orthorectified color (3-band) aerial photography for the Chicago urban area in Illinois, covering Cook, DuPage, Kane, Lake, McHenry and Will counties. The data are stored in the "as delivered" spatial reference of UTM Zone 16, NAD83 with a 1-foot ground resolution.

The mosaic was constructed using georeferenced GeoTIFFs with ArcCatalog 9.1, ArcSDE 9.1 and Oracle 10g. They are stored in the SDE database with LZ77 (non-lossy) compression and exact pixel registration to the original images. The raster consumes 409 gigabytes in the SDE database, has 13.4 million database rows, and 120 billion pixels.

If viewed in ArcMap, a more photo-realistic rendering can be obtained by setting the symbology to use a maximum-minimum stretch. Do not set the display to use any kind of histogram function - this attempts to read every row from the database and will freeze your software.

The original USGS metadata for the source images is included with this XML metadata document as a binary attachment. Excerpts have been included in this metadata.

[Begin excerpt from original metadata]

An orthoimage is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthoimagery combines the image characteristics of a photograph with the geometric qualities of a map. The projected coordinate system is UTM with a NAD83 datum. There is no image overlap between adjacent files.

[End excerpt from original metadata]

Supplemental_Information:
[Begin excerpt from original metadata]

The data obtained through The Seamless Server is considered to be the "best available" data from USGS. Historical data and other data may be obtained by contacting Customer Services, Center for Earth Resources Observation & Science, at 1-800-252-4547. Information in quotation marks, initial processing steps, accuracy reports, and source information is taken directly from the original metadata. Spatial-specific information not available.

[End excerpt from original metadata]

  1. How should this data set be cited?

    Illinois State Geological Survey, 20060413, Mosaic of Chicago Urban Area Color Aerial Photography, 2005: ISGS GIS Database IL_CUA_2005_MOSAIC_UTM16_RAS, Illinois State Geological Survey, Champaign, IL.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -88.722164
    East_Bounding_Coordinate: -87.506905
    North_Bounding_Coordinate: 42.514205
    South_Bounding_Coordinate: 41.192507

  3. What does it look like?

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

    Beginning_Date: 28-Mar-2005
    Ending_Date: 08-Apr-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 485000 x 330000 x 1, type Pixel

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

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 16
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -87.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 0.300000
      Ordinates (y-coordinates) are specified to the nearest 0.300000
      Planar coordinates are specified in meters

      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 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    [Begin excerpt from original metadata]

    Natural color orthoimagery is organized in three color bands or channels which represent the red, green, and blue (RGB) portions of the spectrum. Each image pixel is assigned a triplet of numeric values, one for each color band. Numeric values range from 0 to 255. Areas where data is incomplete due to lack of full image coverage are represented with the numeric value of 0.

    [End excerpt from original metadata]

    Entity_and_Attribute_Detail_Citation:
    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?

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

    Contact_Instructions: Please refer to the Distribution Information section.


Why was the data set created?

This raster can serve a variety of purposes, from interim maps to field references for earth science investigations and analysis. It is a useful GIS layer for comparison of gross changes in ground condition over time, and revision of digital line graphs and topographic maps. It is extremely useful as a general spatial reference.

These data are appropriate for use in local and regional thematic analysis. The data are not appropriate as a geodetic, legal or engineering base. The data set can serve as an important base cartographic element for many types of maps. The data set was not and is not intended as a substitute for surveyed locations, such as can be determined by a registered Public Land Surveyor. Although useful in a GIS as a reference base layer for maps, the data set has no legal basis in the definition of boundaries or property lines.

[Begin excerpt from original metadata]

These data have been created as a result of the need for having geospatial data immediately available and easily accessible in order to provide geographic reference for Federal, State, and local emergency responders, as well as for homeland security efforts. Orthoimages also serve a variety of purposes, from interim maps to field references for earth science investigations and analysis. The digital orthoimage is useful as a layer of a geographic information system. These data can be used to provide reference information for Web browsers and for map applications at a scale of 1:100,000 or smaller. Larger scale orthoimagery such as digital orthophoto quadrangles will be more accurate, but often at the expense of timely updates.

[End excerpt from original metadata]


How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 2)
    USGS, 2005, Chicago Urban Area Aerial Photography Collection:.

    Other_Citation_Details:
    The collection included 4527 1-foot resolution, georeferenced, color (3-band) GeoTIFF images.
    Type_of_Source_Media: Single FireWire external computer hard drive
    Source_Contribution: Delivery medium for imagery

    (source 2 of 2)
    , Other Sources.

    Other_Citation_Details:
    Refer to sources listed in original metadata file, included as a binary attachment in this XML file.

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

    Date: 28-Mar-2005 (process 1 of 1)
    [Begin excerpt from original metadata]

    Two thousand four hundred five photos were aerotriangulated to support digital ortho image production for the following six Illinois counties: Mc Henry, Lake, Kane, Du Page, Cook and Will. Airborne GPS data was provided by AERO-METRIC, Inc and ground checkpoint data was provided by USGS. The project was referenced to the North American Datum of 1983 (NAD83), UTM Zone 16 horizontally and to the North American Vertical Datum of 1988 (NAVD88) vertically. Units were in meters.

    The scanned images (14 micron), ABGPS data, ground checkpoint data, and camera calibration data were used as inputs to the Zeiss/Intergraph ImageStation Automatic Triangulation (ISAT) softcopy program. ISAT correlated image points and aerotriangulated the block of images to create exposure station exterior orientations. Lens distortion, atmospheric refraction, and earth curvature were taken in to account during the aerotriangulation process. Thirty-three USGS provided ground checkpoints were manually measured on the imagery. These ground checkpoints were included in the aerotriangulation adjustment as unconstrained points for absolute ground location verification.

    The scale of the aerial photos was 1 inch = 1800 feet. Two Zeiss RMK Top 15 cameras were used. The focal length was 153.048 mm for photography taken on 4/4/05 and 5/4/05 and 152.826 mm for photography taken on 4/8/05 and 4/14/05.

    Rectification was done using the aerotriangulation data, scans, and 30 meter DEM data provided by the county. These rectified images were used to draw seamlines. The images were then dodged. The dodged rectified images were mosaicked, balanced, and cut into final image sheets. The final sheets were viewed and artifacts were removed as well as other edits performed."

    [End excerpt from original metadata]

    Person who carried out this activity:

    c/o Aero-Metric, Inc
    4020 Technology Parkway
    Sheboygan, WI 53083
    USA

    920-457-3631 (voice)
    jnugent@aerometric.com

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

    , ISGS Terms of Use.

    Online Links:

    , University of Illinois Web Privacy Notice.

    Online Links:

    , University Copyright Policy (stated in the General Rules Concerning University Organization and Procedure, Article III, Section 4).

    Online Links:

    , Policy on Appropriate Use of Computers and Network Systems at the University of Illinois at Urbana-Champaign.

    Online Links:


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    [Begin excerpt from original metadata]

    Radiometry is verified by visual inspection of the digital orthophoto. Slight systematic radiometric differences may exist between adjacent orthoimage files; these are due primarily to differences in source image capture dates and sun angles along flight lines. These differences can be observed in an image's general lightness or darkness when it is compared to adjacent orthoimage file coverages. Tonal balancing may be performed over a group of images during the mosaicking process which may serve to lighten or darken adjacent images for better color tone matching.

    [End excerpt from original metadata]

    For SDE DOQ mosaic developed by ISGS: Limited testing indicates the RGB values are identical pixel for pixel to the original source GeoTIFFs.

    If viewed in ArcMap, a more photo-realistic rendering can be obtained by setting the symbology to use a maximum-minimum stretch. Do not set the display to use any kind of histogram function - this attempts to read every row from the database and will freeze your software.

  2. How accurate are the geographic locations?

    [Begin excerpt from original metadata]

    Thirty-three (33) QC points were provided by USGS. All of the QC points were at well-defined locations and used in the aerotriangulation solution. The locations of the 33 QC ground points were compared to their positions on the rectified ortho images. The resulting X and Y residuals were used to calculate the NSSDA horizontal accuracy at the 95% confidenence level in meters.

    [End excerpt from original metadata]

    For mosaic developed by ISGS: There is exact pixel-by-pixel registration between the source GeoTIFFs and the SDE mosaic.

  3. How accurate are the heights or depths?

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

    Regarding data "as delivered" by USGS: No information.

    Regarding mosaic as subsequently processed by ISGS: All areas of the Chicago 6-county urban area are represented. There may be some offshore infrastructure in Lake Michigan (e.g. pumping stations) that is not included in the coverage area.

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

    [Begin excerpt from original metadata]

    Logical consistency is implicit in the raster image data structure. Source imagery is cloud free.

    [End excerpt from original metadata]


How can someone get a copy of the data set?

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

Access_Constraints:
ISGS information must be obtained directly from the ISGS or from an authorized distributor. Be aware that ISGS information obtained from an unauthorized third party may have been altered subsequent to original distribution, or may no longer be current.

Any access to these data, Web sites, computer systems, electronic services, and electronic networks is governed by University and campus policies, in particular, but not limited to, the Policy on Appropriate Use of Computers and Network Systems at the University of Illinois at Urbana-Champaign, the ISGS Terms of Use document available at the ISGS Web site, and the University of Illinois Web Privacy Notice.

Links to these are provided in the Cross References section.

Use_Constraints:
ISGS information is the property of and copyrighted by the Board of Trustees of the University of Illinois with all rights reserved.  University copyright policy is stated in the General Rules Concerning University Organization and Procedure, Article III, Section 4. A link is provided in the Cross References section.

Individuals or entities may make fair use of copyrighted ISGS material, such as reproducing a single figure or table, or using a brief text quotation, without obtaining formal permission, but in all cases the Illinois State Geological Survey must be credited as the source of the material. To reproduce ISGS information beyond the fair use standard, permission must be obtained from the ISGS Information Office, 615 East Peabody Drive, Champaign, Illinois 61820, 217-333-4747, isgs@isgs.illinois.edu. License fees and a license agreement may be required, depending on the proposed usage.

Any use of these data is governed by University and campus policies, in particular, but not limited to, the Policy on Appropriate Use of Computers and Network Systems at the University of Illinois at Urbana-Champaign, the ISGS Terms of Use document available at the ISGS Web site, and the University of Illinois Web Privacy Notice. Links to these are provided in the Cross References section.

Map information is to be used at a scientifically and cartographically appropriate scale, that is, at a scale no greater than indicated on the map or as described in the documentation of the map or map data.  Map information is not appropriate for, and is not to be used as, a geodetic, legal, or engineering base. Map information has no legal basis in the definition of boundaries or property lines and is not intended as a substitute for surveyed locations such as can be determined by a registered Public Land Surveyor.

The data do not replace the need for detailed site-specific studies.

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

    Information Office, Illinois State Geological Survey (ISGS), a division of the Institute of Natural Resource Sustainability (INRS) of the University of Illinois
    615 East Peabody Drive
    Champaign, Illinois 61820
    USA

    217-333-4747 (voice)
    isgs@isgs.illinois.edu

    Hours_of_Service: 8:00 a.m. - 4:30 p.m., Monday-Friday, U.S. Central Time
  2. What's the catalog number I need to order this data set?

  3. What legal disclaimers am I supposed to read?

    Refer to the Legal Notices of Terms and Conditions of the University of Illinois Web Privacy Policy (there is a link in the Cross References section) for policy statements regarding the following:

    Disclaimer of Liability Disclaimer of Warranties and Accuracy of Data Disclaimer of Endorsement Disclaimer for External Links Disclaimer of Duty to Continue Provision of Data Security Choice of Law

    By obtaining these data you agree to the provisions of the University of Illinois Web Privacy Policy, regardless of the manner in which the information was obtained.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    The data are intended for use with GIS software. The ISGS uses ESRI ArcGIS software, however, ESRI formats can be imported into many different GIS software packages. It is expected that customers who obtain these data have the technical expertise to use GIS software. The ISGS does not provide software support of any kind.


Who wrote the metadata?

Dates:
Last modified: 24-Feb-2009
Metadata author:

Contact_Instructions: Please refer to the Distribution Information section.
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:


Illinois Natural Resources Geospatial Data Clearinghouse

Generated by mp version 2.8.25 on Wed Apr 08 13:31:46 2009