Mosaic of Illinois 7.5-minute Digital Raster Graphic (DRG) Images

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Frequently-anticipated questions:


What does this data set describe?

Title:
Mosaic of Illinois 7.5-minute Digital Raster Graphic (DRG) Images
Abstract:
This is a statewide ArcSDE Raster Mosaic of USGS DRG images of 7.5-minute topographic quadrangles occurring in Illinois. These are unmodified DRG images as distributed by the USGS, except (1) collar information has been removed for map tiling and (2) the data have been reprojected to the customary ISGS Lambert Conformal Conic projection (NAD 27). The map scale is 1:24,000. The map units are meters. The images were scanned at 250 dpi, giving an approximate raster cell resolution of 2.5 meters.
Supplemental_Information: These data were added to the ISGS SDE database in 200308.
  1. How should this data set be cited?

    Illinois State Geological Survey, 20030815, Mosaic of Illinois 7.5-minute Digital Raster Graphic (DRG) Images: ISGS GIS Database GISDB.IL_DRG_MOSAIC_24K_RAS, Illinois State Geoligical Survey, Champaign, Illinois.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -91.710016
    East_Bounding_Coordinate: -87.248974
    North_Bounding_Coordinate: 42.633004
    South_Bounding_Coordinate: 36.856194

  3. What does it look like?

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

    Calendar_Date: varies
    Currentness_Reference: publication dates of source topographic maps

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

    Geospatial_Data_Presentation_Form: raster digital data

  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 254510 x 145924 x 1, type Pixel

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

      The map projection used is Lambert Conformal Conic.

      Projection parameters:
      Standard_Parallel: 33.000000
      Standard_Parallel: 45.000000
      Longitude_of_Central_Meridian: -89.500000
      Latitude_of_Projection_Origin: 33.000000
      False_Easting: 2999994.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 8.199797
      Ordinates (y-coordinates) are specified to the nearest 8.199829
      Planar coordinates are specified in survey feet

      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.400000.
      The flattening of the ellipsoid used is 1/294.978698.

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    Each raster entity or pixel contains a color index from 0 through 12 referencing a color palette of RGB values from 0 through 255 in which the standard colors used in the DRG are defined.

    USGS DRG Color Palette

    Digital Number Color Red Green Blue

    0 Black 0 0 0 1 White 255 255 255 2 Blue 0 151 164 3 Red 203 0 23 4 Brown 131 66 37 5 Green 201 234 157 6 Purple 137 51 128 7 Yellow 255 234 0 8 Light Blue 167 226 226 9 Light Red 255 184 184 10 Light Purple 218 179 214 11 Light Grey 209 209 209 12 Light Brown 207 164 142

    Entity_and_Attribute_Detail_Citation: USGS Draft Standards for Digital Raster Graphic


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 mosaic was created to provide rapid access to a seamless, statewide layer of Illinois DRGs, which are very 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 serves as an important base cartographic element for many types of maps and has been widely distributed and used outside the ISGS. 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.


How was the data set created?

  1. From what previous works were the data drawn?

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

  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?

    No report.

  2. How accurate are the geographic locations?

    It is believed that import into the SDE raster mosaic using LZ77 compression preserved the exact horizontal positions of the source DRGs. However, given that the source DRGs were at one time reprojected from the "as delivered" UTM coordinate system to the customary ISGS Lambert Conformal Conic projection, some resampling and pixel shift does exist.

  3. How accurate are the heights or depths?

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

    No report.

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

    No report.


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

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