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

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  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?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• 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?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   Kucks, Robert P. , 2005, Terrestrial Radioactivity and Gamma-ray Exposure in the United States and Canada: Gridded geographic images:.

   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:

   • <http://pubs.usgs.gov/of/2005/1413/>

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?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.02. Longitudes are given to the nearest 0.02. Latitude and longitude values are specified in Decimal degrees.

      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 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      

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)

   Value	Definition
   (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)

   Value	Definition
   (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)

   Value	Definition
   (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)

   Value	Definition
   (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

   Value	Definition
   (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 80225-0046
   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.

   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 80225-0046
   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 80225-0046
   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 80225
   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?
   • Availability in digital form:

     Data format:	pixel in format Geotiff Arc-Info image format Size: 40.5

   • Cost to order the data:

Who wrote the metadata?

Dates:

Last modified: 22-Feb-2006

Metadata author:

Robert P. Kucks
U.S. Geological Survey
Box 25046, MS 964
Denver Federal Center
Denver, CO 80225
USA

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

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)