Terrestrial Radioactivity and Gamma-ray Exposure in the United States and Canada: Gridded geographic images

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Frequently anticipated questions:


What does this data set describe?

Title:
Terrestrial Radioactivity and Gamma-ray Exposure in the United States and Canada: Gridded geographic images
Abstract:
Aerial gamma-ray surveys measure the gamma-ray flux produced by the radioactive decay of the naturally occurring elements K-40, U-238, and Th-232 in the top few centimeters of rock or soil. If the gamma-ray system is properly calibrated the data can be expressed in terms of the estimated concentrations of the radioactive elements. A ternary color-composite image was generated by commercial software Geosoft Oasismontaj to map the combination of all three elements.

During the period 1975-83, the U.S. Department of Energy carried out the National Uranium Resource Evaluation (NURE) Program, which included aerial gamma-ray surveys of most of the United States. These data were reprocessed to generate this product.
Supplemental_Information:
Digital Data Series DDS-9 (CD-ROM) contains gridded radiometric geophysical data images that were created for the Decade of North American Geology (DNAG) but only available for the U.S.
  1. How might this data set be cited?
    Kucks, Robert P., 2005, Terrestrial Radioactivity and Gamma-ray Exposure in the United States and Canada: Gridded geographic images:.

    Online Links:

    This is part of the following larger work.

    Duval, Joseph S., Carson, John M., Holman, Peter B., and Darnley, Arthur G., 2005, Terrestrial radioactivity and gamma-ray exposure in the United States and Canada: U.S. Geological Survey Open-File Report 2005-1413.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -168.0
    East_Bounding_Coordinate: -53.0
    North_Bounding_Coordinate: 71.33
    South_Bounding_Coordinate: 25.0
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1999
    Ending_Date: 2005
    Currentness_Reference:
    all available NURE data for the U.S. has been processed
  5. What is the general form of this data set?
  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 2371 x 5823, type pixel
    2. What coordinate system is used to represent geographic features?
      The map projection used is Transverse Mercator (Spherical/DNAG).
      Projection parameters:
      Scale_Factor_at_Central_Meridian: 0.926
      Longitude_of_Central_Meridian: -100.0
      Latitude_of_Projection_Origin: 0
      False_Easting: 0
      False_Northing: 0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 2000
      Ordinates (y-coordinates) are specified to the nearest 2000
      Planar coordinates are specified in meters
      The horizontal datum used is DNAG.
      The ellipsoid used is Sphere.
      The semi-major axis of the ellipsoid used is 6371204.0.
      The flattening of the ellipsoid used is 1/1.0.
  7. How does the data set describe geographic features?
    CCM grid cell
    Gamma-ray flux produced by the radioactive decay of naturally occuring elements expressed in concentrations of radioactive elements
    potassium percentage, uranium and thorium ppm
    expressed in units of percent potassium (percent K) and equivalent concentration of uranium and thorium in ppm (ppm eU & ppm eTh) (Source: Duval, Darnley, and Garrett 1990)
    ValueDefinition
    (no value)Cells lacking color (white) represent areas of no data in image.
    Range of values
    Minimum:0.0
    Maximum:100.0
    Units:percent of element
    Resolution:0.1
    K grid cell
    Gamma-ray flux produced by the radioactive decay of naturally occuring elements, expressed in concentrations of radioactive elements
    potassium percentage
    expressed in units of percent potassium (percent K)
    ValueDefinition
    (no value)Cells lacking color (white) represent areas of no data in image.
    Range of values
    Minimum:0.0
    Maximum:4.0
    Units:percent K
    Resolution:0.1
    Th grid cell
    Gamma-ray flux produced by the radioactive decay of naturally occuring elements, expressed in concentrations of radioactive elements
    thorium concentration
    expressed in units of parts per million equivalent thorium (ppm eTh)
    ValueDefinition
    (no value)Cells lacking color (white) represent areas of no data in image.
    Range of values
    Minimum:0.0
    Maximum:24.0
    Units:ppm eTh
    Resolution:0.1
    U grid cell
    Gamma-ray flux produced by the radioactive decay of naturally occuring elements, expressed in concentrations of radioactive elements
    uranium concentration
    expressed in units of parts per million equivalent uranium (ppm eU)
    ValueDefinition
    (no value)Cells lacking color (white) represent areas of no data in image.
    Range of values
    Minimum:0.0
    Maximum:6.0
    Units:ppm eU
    Resolution:0.1
    exp grid cell
    Gamma-ray flux produced by the radioactive decay of naturally occuring elements, expressed in concentrations absorbed doses
    nanoGrays per hour
    gamma-ray absorbed dose rate
    ValueDefinition
    (no value)Cells lacking color (white) represent areas of no data in image.
    Range of values
    Minimum:0.0
    Maximum:125.0
    Units:nanoGrays per hour
    Resolution:1

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Robert P. Kucks
  2. Who also contributed to the data set?
    The U.S Geological Survey reprocessed the aerial gamma-ray (NURE) data to produce maps showing surface concentrations of potassium, uranium, and thorium for the conterminous United States. These maps have been released as USGS Open-File Reports. Some of the reprocessed data have also been released in profile form. The Canadian Geological Survey data were processed by the Radiation Geophysics Section of the CGS. See Open-File Report 2005-1413 for further references.

    USGS employees: Duval, Riggle, and Snyder Canadian GS employees: Carson, Holman, and Darnley
  3. To whom should users address questions about the data?
    Robert P. Kucks
    U.S. Geological Survey
    Box 25046, MS 964
    Denver Federal Center
    Denver, CO
    USA

    (303) 236-1405 (voice)
    rkucks@usgs.gov

Why was the data set created?

Because uranium, thorium, and potassium concentration data are useful in geologic studies and because the NURE data are the only nationwide database on the natural radiation environment, the U.S. Geological Survey reprocessed the aerial gamma-ray data to produce maps showing surface concentrations of potassium, uranium, and thorium for the conterminous United States.

How was the data set created?

  1. From what previous works were the data drawn?
    Duval, Darnley, and Garrett 1990 (source 1 of 5)
    Duval, Joseph S., Darnley, Arthur G. (editor), and Garrett, Robert G. (editor), 1990, Modern aerial gamma-ray spectrometry and regional potassium map of the conterminous United States: Journal of Geochemical Exploration Volume 39, Issues 1-2, December 1990, pages 249-253.

    Online Links:

    Type_of_Source_Media:Source_Contribution: Material re-processed to obtain the present grids
    OFR 90-338 (source 2 of 5)
    Duval, Joseph S., Jones, William J., Riggle, Frederick R., and Pitkin, James A., 1990, Potassium and thorium maps of the conterminous United States: U.S. Geological Survey Open-File Report 90-338.

    Type_of_Source_Media: CD-ROM
    Source_Contribution: Material re-processed to obtain the present grids
    DDS-9 (source 3 of 5)
    Phillips, Jeffrey D., Duval, Joseph S., and Ambroziak, Russell A., 1993, National geophysical data grids; gamma-ray, gravity, magnetic, and topographic data for the conterminous United States: U.S. Geological Survey Digital Data Series DDS-9.

    Type_of_Source_Media: CD-ROM
    Source_Contribution: Material re-processed to obtain the present grids
    DDS-31 Release 1 (source 4 of 5)
    Duval, Joseph S., 1995, Profiles of gamma-ray and magnetic data for aerial surveys over parts of the Western United States from longitude 108 to 126 degrees W. and from latitude 34 to 49 degrees N: U.S. Geological Survey Digital Data Series DDS-31.

    Type_of_Source_Media: CD-ROM
    Source_Contribution: Material re-processed to obtain the present grids
    DDS-31 Release 2 (source 5 of 5)
    Duval, Joseph S., and Riggle, Frederic E., 1999, Profiles of gamma-ray and magnetic data from aerial surveys over the conterminous United States: U.S. Geological Survey Digital Data Series DDS-31.

    Type_of_Source_Media: CD-ROM
    Source_Contribution: Material re-processed to obtain the present grids
  2. How were the data generated, processed, and modified?
    Date: 2005 (process 1 of 2)
    The gamma-ray data were extracted from the NURE files and Canadian data sets; then projected, gridded, and displayed in a ternary form using the commercial software package Geosoft Oasis Montaj. Three elemental grids were calculated, one each for K, U, and Th, and a fourth that is the composite of each of these, referred to here as CCM. Person who carried out this activity:
    Robert P. Kucks
    U.S. Geological Survey
    Box 25046, MS 964
    Denver Federal Center
    Denver, CO
    USA

    (303)236-1405 (voice)
    rkucks@usgs.gov
    Date: 2005 (process 2 of 2)
    The gamma-ray absorbed dose was calculated using the equation

    D = 13.2 K + 5.48 eU + 2.72 eTh

    where K is the concentration of potassium in units of percent K, eU is the concentration of uranium in ppm, eTh is the concentration of thorium in ppm, and D is the absorbed dose in nanoGrays per hour (nGy/hr). This equation is based upon the equation published by Grasty (see OF Report). The grid of the gamma-ray absorbed dose was calculated using the grids of potassium, uranium, and thorium concentrations. That grid was then displayed in image form using the commercial software package Geosoft Oasismontaj. Person who carried out this activity:
    Robert P. Kucks
    U.S. Geological Survey
    Box 25046, MS 964
    Denver Federal Center
    Denver, CO
    USA

    (303)236-1405 (voice)
    rkucks@usgs.gov
  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?
    make these surveys were calibrated, many of the earlier surveys were done without calibration and conversion to the concentrations of the radioactive elements. Detailed examinations of the digital data available on magnetic tape also showed that many of the "calibrated" surveys do not match the data from other "calibrated" surveys of adjacent areas. For these reasons, the data must be corrected to obtain a consistent data base for the conterminous United States. If the gamma-ray system is properly calibrated the data can be expressed in terms of the estimated concentrations of the radioactive elements.
  2. How accurate are the geographic locations?
    The accuracy was dependent on the flight specifications and tolerances of the Department of Energy during their surveying.
  3. How accurate are the heights or depths?
    The accuracy was dependent on the flight specifications and tolerances of the Department of Energy during their surveying.
  4. Where are the gaps in the data? What is missing?
    Data coverage extends thoroughly across the conterminous US. Significant gaps exist in the coverage of Alaska, especially the area south of the North Slope but north of the Brooks Range, and the Aleutian islands. Central Canada is covered as are most of the Atlantic provinces and eastern Ontario. Large gaps exist in Quebec, the western provinces, and both northern and southwestern Ontario.
  5. How consistent are the relationships among the observations, including topology?
    Although many of the airborne gamma-ray systems used to make these surveys were calibrated, many of the earlier surveys were done without calibration and conversion to the concentrations of the radioactive elements. Detailed examinations of the digital data available on magnetic tape also showed that many of the "calibrated" surveys do not match the data from other "calibrated" surveys of adjacent areas. For these reasons, the data must be corrected to obtain a consistent data base for the conterminous United States.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints: None
  1. Who distributes the data set? (Distributor 1 of 1)
    USGS Map Distribution
    Box 25286, Building 810
    Denver Federal Center
    Denver, CO
    USA

    (888)ASK-USGS (voice)
  2. What's the catalog number I need to order this data set? U.S. Geological Survey Open-File Report 2005-1413
  3. What legal disclaimers am I supposed to read?
    The USGS has made every effort to verify the veracity of this information, but is not liable for any inaccuracies.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 07-Dec-2016
Metadata author:
Peter N Schweitzer
USGS Eastern Mineral and Environmental Resources Science Center
Geologist
12201 Sunrise Valley Drive
Reston, VA
USA

703-648-6533 (voice)
703-648-6252 (FAX)
pschweitzer@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://mrdata.usgs.gov/metadata/narad.faq.html>
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