Digital Elevation Model (DEM) of Illinois at 1:250,000

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Frequently-anticipated questions:


What does this data set describe?

Title: Digital Elevation Model (DEM) of Illinois at 1:250,000
Abstract:
This raster dataset consists of edge-matched USGS 1:250,000 DEM tiles for Illinois. Cell size is 301 feet and cell values are elevations in meters above mean sea level rounded to the nearest integer. The data include all of Illinois and extend approximately nine miles beyond the state boundary. Some elevation data at the edges of individual DEM tiles were smoothed to remove edge-matching faults.
Supplemental_Information:
This dataset was transferred to storage in ArcSDE on 20060926. This edition is designated 20060926. The previous edition (1.0) was an ArcInfo grid called allst-int.
  1. How should this data set be cited?

    Abert, Curtis C., 1995, Digital Elevation Model (DEM) of Illinois at 1:250,000: ISGS GIS Database GISDB.IL_DEM_301FT_RAS, Illinois State Geological Survey, Champaign, Illinois, USA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -91.7023
    East_Bounding_Coordinate: -87.1183
    North_Bounding_Coordinate: 42.6501
    South_Bounding_Coordinate: 36.8031

  3. What does it look like?

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

    Calendar_Date: 1995
    Currentness_Reference: Date of additional ISGS processing to USGS data.

  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 7021 x 4240 x 1, type Grid Cell

    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 301.930524
      Ordinates (y-coordinates) are specified to the nearest 301.930524
      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.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: unknown
      Altitude_Resolution: 1.000000
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    IL_DEM_301FT

    ObjectID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Value
    Elevation in meters

    Count

    Entity_and_Attribute_Overview:
    Cell values are elevation above mean sea level in meters rounded to the nearest integer.
    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?

    Contact_Instructions: Please refer to the Distribution Information section.


Why was the data set created?

These data were assembled to provide a statewide database of surface elevation points suitable for analyses of statewide geologic phenomena associated with elevation. The data have been used to generate slope data and shaded relief images, and are appropriate for other such regional applications.

These data are appropriate for use in local and regional elevation analysis. The data are not appropriate as a geodetic, legal or engineering base. The data set can serve as an important base cartographic and analytical element for many types of maps. The data set was not and is not intended as a substitute for surveyed elevations, such as can be determined by a registered Public Land Surveyor.


How was the data set created?

  1. From what previous works were the data drawn?

    none (source 1 of 1)
    United States Geological Survey, unknown, 1:250,000 Digital Elevation Models: USGS DEMs All tiles necessary to provide complete coverage of Illinois, including a 9 mile buffer, USGS, unknown.

    Type_of_Source_Media: digital files
    Source_Scale_Denominator: 250000
    Source_Contribution: elevation grid cells

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

    Date: 1995 (process 1 of 2)
    The ultimate source of the data used to create this data set are United States Geological Survey 1:250,000 3-arc-second Digital Elevation Model Data (DEMs). All or parts of 29 DEM tiles are needed for contiguous coverage of Illinois. The individual DEMs were converted to ARC/INFO lattices (with the ARC LATTICEMERGE command), projected (PROJECT), and clipped to an area of at least 9 miles beyond the state boundary (LATTICECLIP), and stored as an Arc/Info grid.

    (process 2 of 2)
    This dataset was transferred to storage in ArcSDE on 20060926. This edition is designated 20060926. The previous edition (1.0) was an ArcInfo grid called allst-int.

    Metadata updated.

    Person who carried out this activity:

  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?

    Derived from United States Geological Survey 1:250,000-scale 3 arc-second Digital Elevation Model data. Contact the USGS for attribute accuracy of the source DEM data. Some elevation data at the edges of individual DEM tiles were smoothed for edge-matching purposes.

  2. How accurate are the geographic locations?

    Assumed to be as accurate as USGS 3 arc-second DEMs.

  3. How accurate are the heights or depths?

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

    USGS 3 arc-second DEMs projected into Lambert Conformal Conic projection were resampled to an approximate 301 foot cell size.

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

    Not applicable to grids.


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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