Sub-regional, merged, gridded airborne geophysical data

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Frequently anticipated questions:


What does this data set describe?

Title: Sub-regional, merged, gridded airborne geophysical data
Abstract:
Merged grids of residual magnetic intensity, digital terrain model, and apparent resistivity compiled from the Black Mountain, Liscum, Goodpaster, SE extension of Salcha River - Pogo, and Salcha River Pogo geophysical surveys.
Supplemental_Information:
bm_lis_go_sesrp_srp:    Geosoft-format binary grids, GeoTiff format gridded data images, KMZ/KML files, Geosoft ASCII polygon files (PLY), Geosoft ASCII zone files, ESRI Shapefiles, and ERMapper files. Note: these data are provided in both UTM Zone 6 - NAD27 and Geographic WGS84 projections. The data files were compiled from the  Black Mountain, Liscum, Goodpaster, SE extension of Salcha River - Pogo, and Salcha River Pogo  geophysical surveys.
  1. How should this data set be cited?

    Geoterrex-Dighem, Surveys, Fugro Airborne, Stevens Exploration Management Corp., Pritchard, R.A., Burns, L.E., Emond, A.M., and Staff, DGGS, 2016, Sub-regional, merged, gridded airborne geophysical data: Digital Data Series DDS 12, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -145.8169990
    East_Bounding_Coordinate: -143.9942891
    North_Bounding_Coordinate: 64.9825493
    South_Bounding_Coordinate: 64.1790974

  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: ground condition

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

    Geospatial_Data_Presentation_Form: 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.

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

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 6
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -147
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.000000
      False_Northing: 0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest .00000001
      Ordinates (y-coordinates) are specified to the nearest .00000001
      Planar coordinates are specified in Meters

      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 6378206.4.
      The flattening of the ellipsoid used is 1/294.9786982.

  7. How does the data set describe geographic features?

    bm_lis_go_sesrp_srp
    Geosoft-format binary grids, GeoTiff format gridded data images, KMZ/KML files, Geosoft ASCII polygon files (PLY), Geosoft ASCII zone files, ESRI Shapefiles, and ERMapper files. Note: these data are provided in both UTM Zone 6 - NAD27 and Geographic WGS84 projections. The data files were compiled from the Black Mountain, Liscum, Goodpaster, SE extension of Salcha River - Pogo, and Salcha River Pogo geophysical surveys. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and contractor.)


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?

    Funding for the originating geophysical surveys was provided by the Alaska Division of Geological & Geophysical Surveys' (DGGS) Airborne Geophysical/Geological Mineral Inventory (AGGMI) program. The geophysical surveys were managed by State of Alaska, Department of Natural Resources (DNR), Division of Geological & Geophysical Surveys (DGGS). The survey data were collected and processed by Fugro Airborne Surveys Corp., and Geoterrex-Dighem. These Merged grids were generated as part of the Black Mountain - Liscum data collection contract.

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

    Alaska Division of Geological & Geophysical Surveys
    GIS Manager
    3354 College Road
    Fairbanks, AK 99709-3707
    USA

    (907)451-5020 (voice)
    dggsgis@alaska.gov

    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays


Why was the data set created?

This electromagnetic and magnetic airborne geophysical survey data compilation is a product of the Alaska Division of Geological & Geophysical Surveys' (DGGS) Airborne Geophysical/Geological Mineral Inventory (AGGMI) program and the Alaska Strategic and Critical Minerals Assessment Capital Improvement Project. The goal of the Alaska Division of Geological & Geophysical Surveys' (DGGS) Airborne Geophysical/Geological Mineral Inventory (AGGMI) program is to enhance the understanding of Alaska's mineral resources and stimulate private-sector mineral development. The program seeks to delineate mineral zones on Alaska State lands that: (1) have major economic value; (2) can be developed in the short term to provide high-quality jobs for Alaskans; and (3) will provide economic diversification to help offset the loss of Prudhoe Bay oil revenue. Candidate lands for this program are identified on the basis of existing geologic knowledge, land ownership, and nominations from Alaska's geologic community. The AGGMI program and resulting new geologic knowledge are recognized worldwide and have encouraged millions of dollars of venture capital expenditures in the local economies of the surveyed mining districts. These venture capital expenditures have led to discovery and delineation of new mineral resources. The multi-year Strategic and Critical Minerals Assessment Capital Improvement Project (SCMA) was established to determine Alaska's geologic potential for rare-earth elements and other minerals that are essential for our modern, technology-based society. This program began in FY2012 with a data survey and compilation of existing information on rare-earth-element occurrences in Alaska, and expanded significantly in FY2013 to include additional critical minerals, re-analyses of existing samples, and obtaining new field and analytical data, including airborne geophysics.


How was the data set created?

  1. From what previous works were the data drawn?

    Alaska Division of Geological & Geophysical Surveys and others, 2002 (source 1 of 4)
    Alaska Division of Geological & Geophysical Surveys, Surveys, Fugro Airborne, Stevens Exploration Management Corp., and Burns, L.E., 2002, Line, gridded, and vector data of airborne geophysical survey data for the southeastern extension of Salcha River-Pogo survey, Goodpaster mining district, east-central Alaska: Geophysical Report GPR 2002-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 DVD
    Type_of_Source_Media: digital data
    Source_Contribution: gridded data

    Burns, L.E. and others, 2005 (source 2 of 4)
    Burns, L.E., Fugro Airborne Surveys Corp., and Stevens Exploration Management Corp., 2005, Line, grid, and vector data for the airborne geophysical survey data of part of the Goodpaster River area, Goodpaster mining district, Interior Alaska: Geophysical Report GPR 2005-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 DVD
    Type_of_Source_Media: digital data
    Source_Contribution: gridded data

    Burns, L.E. and others, 2006 (source 3 of 4)
    Burns, L.E., Fugro Airborne Surveys Corp., and Stevens Exploration Management Corp., 2006, Line, grid, and vector data and plot files for the airborne geophysical survey data of parts of the East Richardson, Liscum, and Black Mountain areas, Interior Alaska: Geophysical Report GPR 2006-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 29 sheets, 1 DVD
    Type_of_Source_Media: digital data
    Source_Contribution: gridded data

    Burns, L.E. and others, 2000 (source 4 of 4)
    Burns, L.E., Geoterrex-Dighem, and Stevens Exploration Management Corp., 2000, CD-ROM containing profile and gridded data and section line of 2000 geophysical survey data for the Salcha River-Pogo mining area, central Alaska: Geophysical Report GPR 2000-21, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 DVD
    Type_of_Source_Media: digital data
    Source_Contribution: gridded data

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

    Date: 2011 (process 1 of 4)
    Gridded data - The gridded data from the Black Mountain, Liscum, Goodpaster, SE extension of Salcha River - Pogo, and Salcha River Pogo geophysical surveys were merged. The diurnally corrected magnetic data were adjusted for regional variations i.e. IGRF gradient, The residual grids of all the areas may therefore have different base values dependent on the IGRF model used for each grid. The grids were adjusted to each other prior to the final merge. The apparent resistivity grids for 56,000 Hz, 7200 Hz, and 900 Hz coplanar EM data were merged with no reprocessing. Oasis Montaj grid "Suture" technique with the "No De-trending" option was used to merge the grids. The process requires selecting a "master" grid or the grid that all other grids will be levelled to. The grid that was published first is usually chosen and the grid from the most recent survey was selected as the secondary grid (i.e. the grid that will be DC shifted to the master grid).

    Data sources used in this process:

    • Alaska Division of Geological & Geophysical Surveys and others, 2002
    • Burns, L.E. and others, 2005
    • Burns, L.E. and others, 2006
    • Burns, L.E. and others, 2000

    Date: 2016 (process 2 of 4)
    Projection assignment - All Geosoft grids were missing projection information. These data were projected to UTM Zone 6 N NAD27 meters in accordance to the project report of the Liscum survey. Geosoft version 8.5 was used to assign projections to the grids.

    Date: 2016 (process 3 of 4)
    Boundary - DGGS staff constructed a boundary of the merged grid file. The grid boundary was constructed using Geosoft Oaisis montaj grid outline and map export functions. The boundary file is available in Geosft PLY ASCII format and ESRI Shapefile format.

    Date: 2016 (process 4 of 4)
    Google Earth KMZ files - DGGS staff created Google Earth KMZ/KML files from the grid files data using ESRI ArcGIS software.

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

    Geological Survey of Canada, and U.S. Geological Survey, 2015, Yukon - Eastern Alaska magnetic grid: Natural Resources Canada, Canada.

    Online Links:


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

  1. How well have the observations been checked?

    All originating data met contract specifications with a few exceptions due to difficult operational conditions. These exceptions did not noticeably impact data quality. Additional detail about contract specifications and operational issues can be found in the metadata of the originating surveys.

  2. How accurate are the geographic locations?

    All originating data were positioned by DGPS (Differential Global Positioning System) with an accuracy of 5 meters or better.

  3. How accurate are the heights or depths?

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

    Helicopter and fixed wing geophysical surveys often have small data gaps that do not negatively impact the overall quality of the final products. Reference the metadata for each originating survey for specific details.

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

    These data originate from multiple similar geophysical surveys with different specifications. Reference the metadata of each originating survey for exact specifications.


How can someone get a copy of the data set?

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

Access_Constraints:
This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).
Use_Constraints:
Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

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

    Alaska Division of Geological & Geophysical Surveys
    3354 College Road
    Fairbanks, AK 99709-3707
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov

    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (<http://www.dggs.alaska.gov>) for the latest information on available data. Please contact us using the e-mail address provided above when possible.
  2. What's the catalog number I need to order this data set?

    DDS 12

  3. What legal disclaimers am I supposed to read?

    The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 29-Mar-2016
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Metadata Manager
3354 College Road
Fairbanks, AK 99709-3707
USA

(907)451-5020 (voice)

Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:


Generated by mp version 2.9.21 on Tue Mar 29 14:35:35 2016