Electromagnetic and magnetic airborne-geophysical survey of the Liberty Bell area, western Bonnifield mining district, Alaska (data compilation)

Metadata also available as - [Parseable text] - [XML]

Frequently anticipated questions:


What does this data set describe?

Title:
Electromagnetic and magnetic airborne-geophysical survey of the Liberty Bell area, western Bonnifield mining district, Alaska (data compilation)
Abstract:
The Liberty Bell geophysical survey was originally flown in 2001 and published in 2002 (Alaska Division of Geological & Geophysical Surveys and others, 2002) as a part of the State of Alaska's Airborne Geophysical/Geological Mineral Inventory (AGGMI) program. This publication supersedes the previous publications to provide a compilation of published and unpublished information and includes standardized databases and product formats, upgrades digital datasets to modern formats, and re-releases the historical survey and associated documentation (<http://doi.org/10.14509/29690>). This publication contains geophysical data produced from airborne surveys flown from the 24th to 27th of August 2001 for 2,023.6 line kilometers at 400m line spacing in the Bonnifield mining district, Alaska. This DIGHEMV electromagnetic/magnetic survey was flown by Fugro Airborne Surveys Corp. under contract to Stevens Exploration Management Corp.
Supplemental_Information:
ascii_data:    ascii format final and raw data with readme files, ascii format gridded data, Geosoft format import template with extension .iO for final ascii data
databases_geosoft:    Geosoft format database of final line data with readme files; note: these data are provided in both UTM NAD27 and geographic WGS84 projections.
documents:    Field operations report, gridded data explanations, survey background information, processor notes.
grids_ermapper:    Geographically registered gridded data, ER Mapper ERS format.
grids_geosoft:    Geosoft-format binary grids, these grids can be viewed in ESRI ArcMap using a free plugin from Geosoft.
images_registered:    GeoTiff format images of all gridded data.
kmz:    Google Earth kmz files of all gridded data; note: these files use the WGS84 datum.
maps_pdf_format:    Printable maps in pdf format.
maps_prn_format:    Printable maps in HPGL/G printer file format with extension .prn.
profiles_stacked_pdf:    Electromagnetic and magnetic data profiles with EM anomalies, files in PDF format
profiles_stacked_prn:    Electromagnetic and magnetic data profiles with EM anomalies, files in PRN format
vector_data:    Line path, data contours, and survey boundary in ESRI shape file (SHP) and Autocad (2000) DXF formats.
  1. How should this data set be cited?

    Surveys, Fugro Airborne, Stevens Exploration Management Corp., Burns, L.E., and Graham, G.R.C., 2018, Electromagnetic and magnetic airborne-geophysical survey of the Liberty Bell area, western Bonnifield mining district, Alaska (data compilation): Geophysical Report GPR 2018-10, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 12 p.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -149.161346
    East_Bounding_Coordinate: -148.482612
    North_Bounding_Coordinate: 64.258160
    South_Bounding_Coordinate: 63.990150

  3. What does it look like?

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

    Beginning_Date: 2001
    Ending_Date: 2018
    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?

    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 6378206.40000000037.
      The flattening of the ellipsoid used is 1/294.978698199999997.

  7. How does the data set describe geographic features?

    ascii_data
    ASCII format line data, other ASCII data (Source: Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)

    databases_geosoft
    Geosoft format database of final line data, other Geosoft format databases (Source: Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)

    documents
    Project and field reports, survey background information, gridded data explanations, other documentation (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)

    grids_ermapper
    Geographically registered gridded data, ER Mapper ERS format (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    grids_geosoft
    Geosoft-format binary grids, these grids can be viewed in ESRI ArcMap using a free plugin from Geosoft (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)

    images_registered
    GeoTiff format images of all gridded data (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    kmz
    KML language kmz archive files of project data; note: these files use the WGS84 datum (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)

    maps_pdf_format
    Print format maps in PDF format (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)

    maps_prn_format
    Print format maps in HPGL/G printer file format with extension .prn. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)

    profiles_stacked_pdf
    Electromagnetic and magnetic data profiles with EM anomalies, files in PDF format (Source: Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)

    profiles_stacked_prn
    Electromagnetic and magnetic data profiles with EM anomalies, files in PRN format (Source: Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)

    vector_data
    line path, data contours, em anomalies, interpretation and survey boundary in ESRI shape file (SHP) and Autocad (2000) DXF formats (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Fugro Airborne Surveys Corp. and Stevens Exploration Management Corp.)


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?

    This project was funded by the State of Alaska's Airborne Geophysical/Geological Mineral Inventory (AGGMI) program.

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

    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    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


Why was the data set created?

The Liberty Bell airborne magnetic and electromagnetic survey, located in the northern foothills of the Alaska Range of central Interior Alaska, covers part of the Bonnifield mining district, which contains known intrusion-related and placer gold deposits and occurrences. It is also prospective for porphyry copper +/- gold +/- molybdenum +/- silver, skarn, volcanogenic massive sulfide, and other deposit types. The survey is part of the AGGMI program to acquire data on Alaska's most promising mineral belts and districts aimed at catalyzing private sector exploration.


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 3)
    Alaska Division of Geological & Geophysical Surveys, Surveys, Fugro Airborne, Stevens Exploration Management Corp., and Burns, L.E., 2002, Line, grid, and vector data of airborne geophysical survey data for the Liberty Bell area, western Bonnifield mining district, central Alaska: Geophysical Report GPR 2002-7, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 DVD
    Type_of_Source_Media: paper
    Source_Contribution: Legacy data compilation

    Burns, L.E., 2002 (source 2 of 3)
    Burns, L.E., 2002, Portfolio of aeromagnetic and resistivity maps of the Liberty Bell area, western Bonnifield mining district, central Alaska: Geophysical Report GPR 2002-10, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 14 p
    Type_of_Source_Media: paper
    Source_Contribution: Legacy data compilation

    Pritchard, R.A. and Fugro Airborne Surveys, 2002 (source 3 of 3)
    Pritchard, R.A., and Surveys, Fugro Airborne, 2002, Project report of the airborne geophysical survey of the Liberty Bell area, western Bonnifield mining district, central Alaska: Geophysical Report GPR 2002-9, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 172 p., 1 sheet, scale 1:63,360
    Type_of_Source_Media: paper
    Source_Scale_Denominator: 63360
    Source_Contribution: Data collection, processing, and delivery

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

    Date: 2002 (process 1 of 8)
    Data collection, processing, and delivery - The airborne geophysical data were acquired under contract. The contractor's project report and other supporting documents are in the "documents" digital data package. They provide detailed documentation of the system specifications, data collection, processing, and delivery.

    Data sources used in this process:

    • Alaska Division of Geological & Geophysical Surveys and others, 2002
    • Pritchard, R.A. and Fugro Airborne Surveys, 2002

    Date: 2016 (process 2 of 8)
    Legacy data compilation - DGGS staff compiled and organized previously published data and the originating data from the contractor. Original vector data were converted into ESRI shapefiles using ArcMap 10.3.1's Export to Shapefile tool. In this publication's older products and documentation the magnetic data products have been referred to as Total Field Magnetics on the maps and the MAGIGRF channel in the line data and 'magigrf' as a filename abbreviation. The new term 'sim_magtf' has been created to rename and clarify that the data are not representative of the true total magnetic field as the IGRF values have been removed with a single average IGRF value added back to the data, resulting in the IGRF gradient being removed. The term simulated magnetic total field and the filename abbreviation 'sim_magtf' is now used to identify the final magnetic data.

    Data sources used in this process:

    • Burns, L.E., 2002

    Date: 2016 (process 3 of 8)
    Data in Geosoft GDB format - These data were created by importing the final ASCII data into Geosoft Oasis montaj v8.5.1 using the created *.iO import file.

    Date: 2016 (process 4 of 8)
    Geographically registered gridded data in Geosoft GRD format - DGGS assigned missing projection info to grids as needed using Geosoft Oasis Montaj v8.5.1.

    Date: 2016 (process 5 of 8)
    Geographically registered gridded data in GeoTiff format - These data were created by DGGS using Geosft Oasis Montaj v8.5.1. Geosoft grd files were displayed in Geosoft and exported to GeoTiff. A matching colorbar for each grid was displayed in Geosoft and export as a GeoTiff.

    Date: 2016 (process 6 of 8)
    Google Earth KMZ files - Created Google Earth KMZ files from the GeoTiff format gridded data using ESRI ArcGIS 10.3.1.

    Date: 2016 (process 7 of 8)
    Boundary polygon - The boundary polygon was generated by loading the final line data in Geosoft Oasis Montaj v8.5.1. The final magnetic data were gridded using the Minimum Curvature option with the following settings: grid cell size = 1/5 of line spacing, blanking distance = double the line spacing, cells to extend beyond data = 0. The polygon file was created using Grid Outline tool with edge resolution = 1. The polygon file was exported to ESRI shapefile.

    Date: 2017 (process 8 of 8)
    ErMapper ERS files - Created ErMapper ERS files from grids using Geosoft grid utility, Copy/Convert. Using the ErMapper (*.ers) convert option, transfers the grid value to the .ers format file. The .ers format data created from GeoSoft 9.1.

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

    Athey, J.E., Newberry, R.J., Werdon, M.B., Freeman, L.K., Smith, R.L., and Szumigala, D.J., 2006, Bedrock geologic map of the Liberty Bell area, Fairbanks A-4 Quadrangle, Bonnifield mining district, Alaska: Report of Investigation RI 2006-2 v. 1.0.1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 98 p., 1 sheet, scale 1:50,000
    Burns, L.E., Fugro Airborne Surveys Corp., Stevens Exploration Management Corp., Graham, G.R.C., and Emond, A.M., 2016, Bonnifield mining district electromagnetic and magnetic airborne geophysical survey, data compilation: Geophysical Report GPR 2016-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:


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

  1. How well have the observations been checked?

    Geophysical data were acquired according to contractor, contract, and request for proposals specifications. These data are positioned with differential GPS. The magnetometer used had a sensitivity of 0.01 nT. Resistivity sensitivity varies among the different frequencies from 0.06 ppm to .60 ppm. Details are given in the Liberty Bell project report found at <http://doi.org/10.14509/29690>

  2. How accurate are the geographic locations?

    The helicopter position was derived every 0.5 seconds using post-flight differential positioning to a relative accuracy of better than 10 m. Positional accuracy of the presented data is better than 5 m with respect to the UTM grid. Further inaccuracies may be introduced by the interpolation and gridding process. These data are positioned with post processed differential GPS.

  3. How accurate are the heights or depths?

    Manufacturer's accuracy on the radar altimeter used during data acquisition is 3.0 meters. The accuracy of the elevation calculation used for the digital terrain model is directly dependent on the accuracy of the two input parameters, ALTR and GPS-Z. The ALTR value may be erroneous in areas of heavy tree cover, where the altimeter reflects the distance to the tree canopy rather than the ground. The GPS-Z value is primarily dependent on the number of available satellites. Although post-processing of GPS data will yield X and Y accuracies in the order of 5 meters, the accuracy of the Z value is usually much less, sometimes in the +/-20 meter range. Further inaccuracies may be introduced during the interpolation and gridding process. These data are positioned with post processed differential GPS.

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

    This publication release provides the entire dataset generated by this project.

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

    Geophysical data were acquired according to contractor, contract, and request for proposals specifications. These data are positioned with differential GPS. The originating coordinate system was retained for all publication products except the KMZ files, which utilize WGS84 geographic coordinates. In some cases, values are provided in both UTM NAD27 and geographic WGS84 projections.


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
    Metadata Manager
    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
  2. What's the catalog number I need to order this data set?

    GPR 2018-10

  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: 22-Jun-2018
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
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
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:


Generated by mp version 2.9.21 on Fri Jun 22 14:15:36 2018