Nyac magnetic airborne geophysical survey data compilation

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?

   Burns, L.E., Barefoot, J.D., Woods, Rebecca-Ellen, WGM Mining and Geological Consultants, Inc., and Dighem Surveys and Processing, 2019, Nyac magnetic airborne geophysical survey data compilation: Geophysical Report GPR 2019-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/30169>

   Other_Citation_Details: 3 p.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -160.163260

   East_Bounding_Coordinate: -159.638530

   North_Bounding_Coordinate: 61.131602

   South_Bounding_Coordinate: 60.903286

3. What does it look like?

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

   Calendar_Date: 1993

   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: 4

      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.999600

      Longitude_of_Central_Meridian: -159

      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: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing)

   databases_geosoft

   Geosoft format database of line data, other Geosoft format databases (Source: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing)

   documents

   Project and field reports, survey background information, gridded data explanations, other supporting documentation (Source: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing and Alaska Division of Geological & Geophysical Surveys (DGGS))

   grids_ermapper

   Geographically registered gridded data, ER Mapper ERS format (Source: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing and 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: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing and Alaska Division of Geological & Geophysical Surveys (DGGS))

   images_registered

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

   kmz

   Keyhole markup language (kml) kmz archive files of project data. Viewable in Google Earth and other compatible programs (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

   maps_pdf_format

   Printable maps in pdf format (Source: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing)

   maps_prn_format

   Printable maps in HPGL/2 printer file format with extension .prn (Source: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing)

   profiles_stacked

   Distance-based profiles of the digitally recorded geophysical data are generated and plotted at an appropriate scale. The profiles display electromagnetic anomalies with their respective interpretive symbols (Source: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing)

   vector_data

   Line path, data contours, and survey boundary in ESRI shapefile (SHP) format, ESRI Geodatabase format, and/or AutoCAD dxf format (Source: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing and Alaska Division of Geological & Geophysical Surveys (DGGS))

   video_flightpath

   Survey flight path downward-facing video (Source: WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing)

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Burns, L.E.
   • Barefoot, J.D.
   • Woods, Rebecca-Ellen
   • WGM Mining and Geological Consultants, Inc.
   • Dighem Surveys and Processing

2. Who also contributed to the data set?

   Funding was provided by the Alaska State Legislature as part of the DGGS 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?

This airborne geophysical survey is part of a program to acquire data on Alaska's most promising mineral belts and districts. The information acquired is aimed at catalyzing new private sector exploration, discovery, and ultimate development and production. The purpose of the survey was to map the magnetic properties of the survey area, which has been an important producer of placer gold since 1908. Other gold and base-metal anomalies, altered zones, favorable lithologies, and structural zones are known to exist throughout the survey area.

How was the data set created?

1. From what previous works were the data drawn?

   Alaska Division of Geological & Geophysical Surveys and others, 1994 (source 1 of 8)

   Alaska Division of Geological & Geophysical Surveys, WGM, Inc., and Dighem, 1994, Clear mylar version of RI 94-3: Total field magnetics of the Nyac mining district: Public Data File PDF 94-18, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/1643>

   Other_Citation_Details: 1 sheet, scale 1:63,360

   Type_of_Source_Media: paper

   Source_Scale_Denominator: 63360

   Source_Contribution: Data collection, processing, and delivery

   Alaska Division of Geological & Geophysical Surveys and others, 1994 (source 2 of 8)

   Alaska Division of Geological & Geophysical Surveys, WGM, Inc., and Dighem, 1994, Filtered total field VLF contours of Nyac mining district: Public Data File PDF 94-17, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/1642>

   Other_Citation_Details: 1 sheet, scale 1:63,360

   Type_of_Source_Media: paper

   Source_Scale_Denominator: 63360

   Source_Contribution: Data collection, processing, and delivery

   Alaska Division of Geological & Geophysical Surveys and others, 1994 (source 3 of 8)

   Alaska Division of Geological & Geophysical Surveys, WGM, Inc., and Dighem, 1994, Flight lines of Nyac mining district: Public Data File PDF 94-16, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/1641>

   Other_Citation_Details: 1 sheet, scale 1:63,360

   Type_of_Source_Media: paper

   Source_Scale_Denominator: 63360

   Source_Contribution: Data collection, processing, and delivery

   Burns, L.E. and others, 2004 (source 4 of 8)

   Burns, L.E., Fugro Airborne Surveys Corp., and Stevens Exploration Management Corp., 2004, Line, gridded, and vector data, and selected plot files from the aeromagnetic survey of the Nyac mining district, central Alaska: Geophysical Report GPR 2004-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/3338>

   Other_Citation_Details: 1 DVD

   Type_of_Source_Media: paper

   Source_Contribution: Data collection, processing, and delivery

   DGGS Staff and others, 1994 (source 5 of 8)

   Staff, DGGS, Dighem, and WGM, Inc., 1994, CD-ROM digital archive files of 1993 survey data for Nome, Circle, Nyac, and Valdez Creek mining districts: Public Data File PDF 94-15, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/1640>

   Other_Citation_Details: 22 p., 1 DVD

   Type_of_Source_Media: paper

   Source_Contribution: Data collection, processing, and delivery

   DGGS Staff and others, 1994 (source 6 of 8)

   Staff, DGGS, WGM, Inc., and Dighem, 1994, Digital gridded data of total field magnetics for entire survey of Nyac mining district: Public Data File PDF 94-34, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/1660>

   Other_Citation_Details: 1 DVD

   Type_of_Source_Media: paper

   Source_Contribution: Data collection, processing, and delivery

   DGGS Staff and others, 1994 (source 7 of 8)

   Staff, DGGS, WGM, Inc., and Dighem, 1994, Total field magnetics of the Nyac mining district: Report of Investigation RI 94-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/2489>

   Other_Citation_Details: 1 sheet, scale 1:63,360

   Type_of_Source_Media: paper

   Source_Scale_Denominator: 63360

   Source_Contribution: Data collection, processing, and delivery

   McConnell, D.L., 1994 (source 8 of 8)

   McConnell, D.L., 1994, Final summary of 1993 airborne geophysical surveys of the Nome, Circle, Nyac, and Valdez Creek areas: Public Data File PDF 94-36, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/1662>

   Other_Citation_Details: 327 p., 4 sheets, 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: 1993 (process 1 of 9)

   Data collection, processing, and delivery - The airborne geophysical data were acquired under contract with WGM Mining and Geological Consultants, Inc. and Dighem Surveys and Processing. 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, 1994
   • Alaska Division of Geological & Geophysical Surveys and others, 1994
   • Alaska Division of Geological & Geophysical Surveys and others, 1994
   • Alaska Division of Geological & Geophysical Surveys and others, 1994
   • Burns, L.E. and others, 2004
   • DGGS Staff and others, 1994
   • DGGS Staff and others, 1994
   • DGGS Staff and others, 1994
   • McConnell, D.L., 1994

   Date: 2004 (process 2 of 9)

   Reformatting - Digital data collected in 1993 were reformatted for ease of use with modern processing tools, vector files were added, and new color maps were produced. No reprocessing was done.

   Date: 2019 (process 3 of 9)

   Grid development - The analytic signal grid was generated by using the analytic signal function in Geosoft Oasis Montaj v9 on 100m upward continued simulated total magnetic field grid. The calculated first vertical derivative grid was created during the analytic signal process. The derivatives in the analytic signal calculation were computed using a fast Fourier transform (FFT) based 2D filter.

   Date: 2019 (process 4 of 9)

   RGB GeoTiff creation - RGB GeoTIFF raster files of gridded data were exported using Geosoft v9 by loading each Geosoft grid onto a map and using the map export tool.

   Date: 2019 (process 5 of 9)

   DXF conversion and geographic referencing - Contractor provided AutoCAD DXF files were converted to an ESRI Geodatabase in ArcMap v10 using the CAD to Geodatabase tool.

   Date: 2019 (process 6 of 9)

   Standard Boundary Polygon - The final boundary polygon was generated by loading the line data in Geosoft Oasis Montaj v9. The channel MAG was gridded using the Minimum Curvature option with the following settings: grid cell size = 25, blanking distance = 800, cells to extend beyond data = 2. The polygon file was created using Grid Outline tool with edge resolution = 1. The polygon file was exported to ESRI shapefile.

   Date: 2019 (process 7 of 9)

   Keyhole markup language (kml) KMZ archive creation - Data were exported from Geosoft and ESRI ArcMap to kml format files and/or KMZ archives. These files were then combined and modified in Google Earth Pro to create the final KMZ file.

   Date: 2019 (process 8 of 9)

   Simulated Magnetic Total Field - 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 MAG channel in the line data and 'mag' 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 value added back to the entire dataset, resulting in the IGRF gradient being removed. The term simulated magnetic total field and the filename abbreviation 'sim_magtf' is now used to identify these magnetic data.

   Date: 2019 (process 9 of 9)

   Data cataloged for archival and publication - All files were renamed and placed in a standardized set of folders according to the DGGS Geophysics Data Management Manual. Where applicable and as needed data were converted to newer file formats and new files were created. Supporting documentation including but not limited to readme text files, maps, figures, survey overview report, missing data type explanations, and metadata were created.

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

   Staff, DGGS, 2014, Airborne GeophysWeb: A compilation of geophysical data from DGGS and cooperating agencies: Digital Data Series DDS 2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/27222>

   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:

   • <http://doi.org/10.14509/29555>

   Other_Citation_Details: 1 DVD

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. For additional detail about survey parameters, see the accompanying project report available in the documents directory of this data distribution package.

2. How accurate are the geographic locations?

   These data are positioned with post-processed differential GPS.

3. How accurate are the heights or depths?

   These data are positioned with post-processed differential GPS.

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

   This data set includes files that contain processed aeromagnetic measurements, electromagnetic measurements, altimetry measurements, and locational data for the entire survey area.

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

   Data originate from one company using the same contract specifications for all data. The originating coordinate system was retained for all publication products.

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 2019-4

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?
   • Availability in non-digital form:

     DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount.

   • Cost to order the data: Contact DGGS for current pricing

   • Availability in digital form:

     Data format:

     DGGS geophysics datasets are typically compilations of multiple digital data file formats. These formats may include: GeoTiff, ESRI shapefile, Geosoft binary grid (GRD), Microsoft Office documents, PDF, ER Mapper ERS, ASCII text files (including CSV), Geosoft ASCII grid (GXF), Geosoft database, AutoCAD DXF, Geosoft plot file (PLT), Printer files (HPP, PRN, or other), digital images (multiple formats), digital video (multiple formats), Geosoft ASCII XYZ, Geosoft ASCII files (PLY, i0, EXP), and KMZ

     Network links:

     <http://doi.org/10.14509/30169>

   • Cost to order the data: Free download

Who wrote the metadata?

Dates:

Last modified: 01-Apr-2019

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:

• <http://www.dggs.alaska.gov/metadata/dggs.ext>