Farewell and Middle Styx survey areas: Project report, interpretation maps, EM anomalies, stacked multi-channel profiles, and other products of the airborne geophysical surveys, parts of the McGrath, Lime Hills, and Tyonek quadrangles, south-central Alaska

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Frequently anticipated questions:

What does this data set describe?

Title:
Farewell and Middle Styx survey areas: Project report, interpretation maps, EM anomalies, stacked multi-channel profiles, and other products of the airborne geophysical surveys, parts of the McGrath, Lime Hills, and Tyonek quadrangles, south-central Alaska
Abstract:
This digital publication, GPR 2014-4, contains CGG's analysis and interpretation of data produced from airborne geophysical surveys published by DGGS in 2013 (GPR 2013-1) and 2014 (GPR 2014-5) for the Middle Styx and Farewell survey areas respectively. The two survey blocks Farewell and Middle Styx are referred to as the 'Farewell' survey in the project report as these blocks were flown under one contract. Elsewhere the separate block names, Farewell and Middle Styx, are typically used. CGG's frequency-domain DIGHEM V system was used for the EM data. GPR 2014-4 includes (1) CGG's project report with interpretation and detailed EM Anomalies, and (2) Multi-channel stacked profiles in pdf format. Interpretation maps and EM anomalies are provided in various formats (e.g., Geotiffs , KMZs, and others) and are listed in detail in gpr2014_004_readme (.txt and .pdf). Other supporting files include gpr2014_004_browsegraphic.pdf, farewell_middlestyx_emanomaly_readme.pdf, farewell_middlestyx_smprofiles_readme.pdf, and many legends as jpgs.
Supplemental_Information:
The airborne data were acquired and processed under contract between the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), and Fugro GeoServices, Inc. Fugro Airborne Surveys (now CGG), the subcontractor, acquired and processed the data in 2012 and 2013. Ownership of Fugro Airborne Surveys was transferred to CGG Canada Services Ltd. during the course of this project. Data acquisition, processing, and the type of products were all the same for the three surveys blocks. The file 'gpr2014_004_readme.pdf' includes file names and definitions and general information. Other supporting files include gpr2014_004_browsegraphic.pdf, farewell_middlestyx_emanomaly_readme.pdf, farewell_middlestyx_smprofiles_readme.pdf, and many legends as jpgs. All data are provided in NAD27, UTM zone 5N, except for Google Earth KMZ files, which are in Geographic Coordinate System (Simple Cylindrical projection) with a WGS84 datum. The bounding coordinates for all three surveys are given below in the 'Spatial_Domain Section'. The bounding coordinates for each survey block is given here. 
FAREWELL: (McGrath and Lime Hills quadrangles)
 West_Bounding_Coordinate: -154.54
 East_Bounding_Coordinate: -152.99
 North_Bounding_Coordinate:  62.52
 South_Bounding_Coordinate:  61.86
MIDDLE STYX: (Lime Hills and Tyonek quadrangles)
 West_Bounding_Coordinate: -153.46
 East_Bounding_Coordinate: -152.97
 North_Bounding_Coordinate:  61.98
 South_Bounding_Coordinate:  61.74
  1. How should this data set be cited?

    CGG, and Fugro GeoServices, Inc., 2015, Farewell and Middle Styx survey areas: Project report, interpretation maps, EM anomalies, stacked multi-channel profiles, and other products of the airborne geophysical surveys, parts of the McGrath, Lime Hills, and Tyonek quadrangles, south-central Alaska: Geophysical Report GPR 2014-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 22 sheets, scale 1:31,680.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -154.54
    East_Bounding_Coordinate: -152.97
    North_Bounding_Coordinate: 62.52
    South_Bounding_Coordinate: 61.74

  3. What does it look like?

    gpr2014_4_browsegraphic.pdf (PDF)
    The browse graphic file contains the location maps showing: 1) survey area and adjacent published surveys within Alaska, 2) detailed location diagram showing the survey area, adjacent surveys, and Cook Inlet Region, Inc. (CIRI) land within the immediate survey area, 4) detailed diagram showing the location of the 63,360-scale map sheets for the Farewell survey, 5) detailed diagram showing the location of the 63,360-scale map sheets for the Middle Styx survey, 6) detailed diagram showing the location of the 31,680-scale map sheets for the Farewell and Middle Styx surveys.

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

    Beginning_Date: Sep-2012
    Ending_Date: Dec-2014
    Currentness_Reference: publication date

  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: 5N
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -153
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000
      False_Northing: 0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.01
      Ordinates (y-coordinates) are specified to the nearest 0.01
      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 1/294.978698.

  7. How does the data set describe geographic features?

    project_report_em_anomalies
    Adobe Acrobat format of CGG's project report with interpretation EM anomaly picks for the report in csv and Geosoft ASCII XYZ formats. 'Farewell_middlestyx_emanom_readme.pdf' included. (Source: CGG)

    geotiffs_kmzs
    Interpretation sheets are provided as GeoTiff and kmz files, and the EM anomaly map images are included as GeoTiffs. (Source: CGG)

    maps_hpgl2
    hpgl2 format (.prn) maps. See gpr2014_004_readme.pdf. (Source: CGG)

    maps_pdf
    Adobe Acrobat (pdf) format maps. See gpr2014_004_readme.pdf. (Source: CGG)

    sm_profiles
    Adobe Acrobat format of CGG's project stacked-multi channel profile. See Project Report for more information. (Source: CGG)

    vectors
    ESRI Shape and Autocad DXF of interpretation, EM anomalies, and various locational reference files. See gpr2014_004_readme.pdf. (Source: CGG)

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 was provided by the Alaska State Legislature for the Strategic and Critical Minerals Capital Improvement Project (CIP), a part of the DGGS Airborne Geophysical/Geological Mineral Inventory (AGGMI) program. Cook Inlet Region, Inc. (CIRI) contributed funding for a portion of the area.

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

    Alaska Division of Geological & Geophysical Surveys
    Geophysics Staff
    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?

The survey was part of the Strategic and Critical Minerals Capital Improvement Project (CIP), a subset of the Alaska Airborne Geophysical/Geological Mineral Inventory Program. The program was funded by the Alaska State Legislature and managed by State of Alaska, Department of Natural Resources (DNR), Division of Geological & Geophysical Surveys (DGGS). The program seeks to catalyze private-sector mineral development investment. The program delineates 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 Alaska; and 3) will provide economic diversification to help offset the loss of Prudhoe Bay oil revenue. Cook Inlet Region, Inc. (CIRI) contributed funding for a portion of the area.

How was the data set created?

  1. From what previous works were the data drawn?

    CGG, 2013 (source 1 of 2)
    CGG, Unpublished material, original raw and processed data, vector files, and test results for the Middle Styx survey area.

    Type_of_Source_Media:
    tabular digital data, raster digital data, vector digital data on DVD
    Source_Contribution:
    A copy of the original raw and final geophysical data from the 2012-2013 Middle Styx survey and other associated files are stored at the CGG office. Rather than using the version released by DGGS in 2013 (GPR2013-2), CGG used the files already available to them to provide data for the interpretation, EM anomaly picks, multichannel-stacked profiles included on this publication.

    CGG, 2014 (source 2 of 2)
    CGG, Unpublished material, original raw and processed data, vector files, and test results for the Farewell survey area.

    Type_of_Source_Media:
    tabular digital data, raster digital data, vector digital data on DVD
    Source_Contribution:
    A copy of the original raw and final geophysical data from the 2012-2013 Farewell survey and other associated files are stored at the CGG office. Rather than using the version released by DGGS in 2014 (GPR2014-2), CGG used the files already available to them to provide data for the interpretation, EM anomaly picks, multichannel-stacked profiles included on this publication.

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

    Date: 2014 (process 1 of 5)
    To determine the location of electromagnetic (EM) anomalies or their boundaries, the DIGHEM(V) EM system measured inphase and quadrature components at five frequencies. Two DIGHEM (V) EM systems were used on this project, one associated with an Aerospatiale AS350B2 helicopter and the other with an Aerospatiale AS350B3 helicopter. The EM systems measured inphase and quadrature components at five frequencies. Two vertical coaxial-coil pairs operated at nominal frequencies of 1000 and 5500 Hz while three horizontal coplanar-coil pairs operated at 900, 7200, and 56,000 Hz. Actual frequencies for the four EM systems used in the Farewell and Middle Styx surveys are listed in the project report (GPR2014-4-4_ProjectReport.pdf; Tables 8-11). The EM data were sampled at 0.1 second intervals and interpolated onto a regular 80m grid using a modified Akima (1970) technique. The EM system responds to bedrock conductors, conductive overburden, and cultural sources. The power line monitor and the flight track video were examined to locate cultural sources. The EM anomalies that are indicated are classified by conductance. EM Anomalies are identified by creating multi-parameter stacked profiles for all survey lines at a scale of 1:31,680. Anomaly grades range from 0 to 7 and are based on calculated conductance. See the Project Report (GPR2014-4-4_ProjectReport.pdf; Tables 18 and 19: EM Anomaly Statistics) for more information. The grade 0 anomaly, denoted by an �X�, indicates that in-phase and quadrature levels are below set thresholds and will not give a reliable calculation of the conductivity. These anomalies are shown with an asterisk (*) in the EM legend on the 1:31,680 scale maps (GPR2014-4-2a through GPR2014-4-2h).

    Data sources used in this process:

    • CGG, 2013
    • CGG, 2014

    Date: 2014 (process 2 of 5)
    Ruth Pritchard, a CGG geophysicist, wrote the project report and the interpretation of the processed geophysical data. For the interpretation maps, Ruth used CGG's in-house copy of the linedata, gridded data, and multi-channel stacked profiles for interpretation of anomalous data, lineations, and potential faults. Geologic references used in this interpretation are cited in the project report.

    Data sources used in this process:

    • CGG, 2013
    • CGG, 2014

    Date: 2014 (process 3 of 5)
    Geophysical images and vectors used on the EM anomaly maps were converted to GeoTIFFs using CGG's specialized software. Vectors used on the interpretation maps were converted to GeoTIFFs and KMZs using CGG's specialized software.

    Date: 2014 (process 4 of 5)
    Two modified sections of the Alaska PLSS Section Grid (Frl_SecGrid and Mst_SecGrid), were taken from CGG's files. The files were also used in DGGS publications GPR2013-2 and GPR2014-2; the process was documented in those publications.

    Data sources used in this process:

    • CGG, 2013
    • CGG, 2014

    Date: 2014 (process 5 of 5)
    The HPGL/2 files were created with HP Designjet T1300ps HPGL driver v61.132.2518.500 and plot on some plotters, but not all plotters correctly. The Adobe Acrobat format files were created with Adobe Acrobat Distiller v9.0 from Postscript files.

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

    Burns, L.E., CGG, and Fugro GeoServices, Inc., 2014, Farewell survey area: Airborne magnetic, electromagnetic and radiometric data in line (point), grid, vector, and map formats, McGrath and Lime Hills quadrangles, south-central Alaska: Geophysical Report GPR 2014-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 DVD, scale 1:63,360
    Burns, L.E., Fugro Airborne Surveys Corp., and Fugro GeoServices, Inc., 2013, Middle Styx survey area: Airborne magnetic, electromagnetic, and radiometric data in line (point), grid, vector, and map formats, Lime Hills and Tyonek quadrangles, southcentral Alaska: Geophysical Report GPR 2013-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 DVD, scale 1:63,360
    Burns, L.E., Fugro Airborne Surveys Corp., and Stevens Exploration Management Corp., 2008, Line, grid, and vector data, and plot files for the airborne geophysical survey of the Styx River Survey, southcentral Alaska: Geophysical Report GPR 2008-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 27 sheets, 1 DVD
    Burns, L.E., CGG, and Fugro GeoServices, Inc., 2014, East Styx survey area: Airborne magnetic, electromagnetic and radiometric data in line (point), grid, vector, and map formats, Talkeetna, Tyonek, McGrath, and Lime Hills quadrangles, south-central Alaska: Geophysical Report GPR 2014-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 DVD, scale 1:63,360

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

  1. How well have the observations been checked?

    Survey interpretation and documentation of data acquisition and tests done during acquisition were produced by the same company (CGG) who acquired the data. Tests completed and constraints used are documented in the project report. Ruth Pritchard, the project report author and data interpreter, has several decades of experience interpreting aeromagnetic and electromagnetic data and making EM anomaly picks.

  2. How accurate are the geographic locations?

    Accuracy of the data was discussed in the metadata for the first publications for Middle Styx (GPR2013-2) and Farewell (GPR 2014-2) surveys (listed in the cross references). The helicopter position was derived every 0.5 seconds using post-flight differential positioning to an accuracy of better than 1 m.

  3. How accurate are the heights or depths?

    The laser altimeter ('ALTLAS_BIRD'), located in the bird (EM equipment and magnetometer housing), had a stated resolution of 0.10 meter. The ALTLAS_BIRD value may be unreliable over bodies of water where the laser returns are scattered.

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

    The data are complete.

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

    N/A

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?

    GPR 2014-4

  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?

  5. What hardware or software do I need in order to use the data set?

    Software with ability to use, import, or convert Geosoft binary GDB or Geosoft ASCII XYZ files, Autocad DXF files, ESRI Shape files, Adobe Acrobat PDF, Google Earth files, and text files. Free downloadable interfaces to view or convert the gridded and dxf files are available at the Geosoft Web site (<http://www.geosoft.com>; Oasis Montaj viewer). The KMZ files can be dragged and dropped into the 'My Places' folder of the free downloadable 'Google Earth' software. Freeware software 'printfile' (<http://www.lerup.com/printfile/>) prints HPGL/2 files easily on compatible printers. The HPGL/2 files have brighter colors and sharper topography than the PDF maps and should be used for printing when possible. The PDF format maps are the only maps digitally viewable in this publication.

Who wrote the metadata?

Dates:
Last modified: 30-Apr-2015
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:

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