Iron Creek airborne electromagnetic and magnetic geophysical survey data compilation

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

Frequently anticipated questions:


What does this data set describe?

Title:
Iron Creek airborne electromagnetic and magnetic geophysical survey data compilation
Abstract:
Frequency domain electromagnetic data and magnetic geophysical data were collected below a helicopter using a 30 meter (m) long line and a towed bird for the 1997 Iron Creek survey. The geophysical data were acquired with a DIGHEM-V Electromagnetic (EM) system, a Scintrex cesium magnetometer, and a Herz VLF system installed in on AS350B-2 Squirrel helicopter. In addition, the survey recorded data from a radar altimeter, GPS navigation system, 50/60 Hz monitors and video camera. Many of the files for this release were published on paper and available by mail order beginning in 1998. This updated data release provides a compilation of the previously published paper files (in PDF format) and the originating data files that were acquired from the contractor. 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 WGM, Inc. Geoterrex-Dighem, the subcontractor, acquired and processed the data in 1997 and 1998.
Supplemental_Information:
Project specifications:
	line km: 5042
	data points: 834052
	start date: 1997-08-06
	end date: 1997-08-24
	Specified Helicopter Terrain Clearance: 60 meters
	Specified Sensor Terrain Clearance: 30 meters
	Production Line Spacing: 400 meters
	Tie Line Spacing: 4800 meters
	Line direction: N 45 W
	Coil orientations/frequencies/Tx-Rx separation:
		coaxial 900 Hz   8.0 meters
		coplanar 900 Hz   8.0 meters
		coaxial 5500 Hz   8.0 meters
		coplanar 7200 Hz   8.0 meters
		coplanar 56,000 Hz   6.4 meters
	Actual Frequencies (Hz):
		August 6, 1997
		Flight 1
	 	coaxial 1070 Hz
		coplanar 864 Hz
 		coaxial 6368 Hz
		coplanar 7294 Hz
		coplanar 55,951 Hz
	August 6, 1997 - August 8, 1997
		Flights 2-8
		coaxial 1070 Hz
		coplanar 888 Hz
		coaxial 6368 Hz
		coplanar 7294 Hz
		coplanar 55,951 Hz
	August 9, 1997 - August 24, 1997
		Flights 9-48
		coaxial 1070 Hz
		coplanar 911 Hz
		coaxial 6368 Hz
		coplanar 7294 Hz
		coplanar 55,951 Hz
	Channels recorded:
		5 inphase channels
		5 quadrature channels
		2 monitor channels
  1. How should this data set be cited?

    Burns, L.E., Geoterrex-Dighem, WGM, Inc., Emond, A.M., and Graham, G.R.C., 2014, Iron Creek airborne electromagnetic and magnetic geophysical survey data compilation: Geophysical Report GPR 2014-6, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -149.65
    East_Bounding_Coordinate: -148.32
    North_Bounding_Coordinate: 62.70
    South_Bounding_Coordinate: 62.25

  3. What does it look like?

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

    Calendar_Date: 1997
    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 1
      Ordinates (y-coordinates) are specified to the nearest 1
      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?

    ascii_data
    ascii format final and raw data with readme files, ascii format gridded data (Source: Dighem and WGM, Inc.)

    documents
    project report, portfilio summary report authored by DGGS, EM anomalies in ascii CSV format (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Dighem, and WGM, Inc.)

    databases_geosoft
    Geosoft format database file with extension .gdb, Geosoft format import template with extension .iO for final ascii data (Source: Dighem and WGM, Inc.)

    grids_ermapper
    geographically registered gridded data, ErMapper ERS format (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Dighem, and WGM, Inc.)

    grids_geosoft
    Geosoft-format binary grids, these grids can be viewed in ESRI ArcMap using a free plugin from Geosoft. Additional explanatory information is included with the download files (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Dighem, and WGM, Inc.)

    images_registered
    GeoTiff format images of all gridded data. Additional explanatory information is included with the download files (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Dighem, and WGM, Inc.)

    maps_pdf_format
    print format maps in pdf format; 2014-14-15 version note: some maps no longer display correctly, additional explanatory information is included with the download files (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Dighem, and WGM, Inc.)

    maps_hpp_format
    print format maps in hpp (printer file) format; 2014-14-15 version note: some maps no longer display correctly, additional explanatory information is included with the download files (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Dighem, and WGM, Inc.)

    vector_data
    line path in ESRI Arc Shapefile format; line path, data contours, EM anomalies, and townships in DXF and PLT format (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Dighem, and WGM, Inc.)

    kmz
    Google Earth kmz files (Source: Alaska Division of Geological & Geophysical Surveys (DGGS), Dighem, and WGM, Inc.)


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?

    The survey was part of the Alaska Airborne Geophysical/Geological Mineral Inventory project funded by the Alaska State Legislature and managed by State of Alaska, Department of Natural Resources (DNR), Division of Geological & Geophysical Surveys (DGGS). The survey data was collected and processed by WGM Inc., Mining and Geologic Consultants; Geoterrex-Dighem a division of CGG Canada Ltd.

  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?

The 1997 Iron Creek airborne electromagnetic and magnetic geophysical survey and this compilation are part of the Alaska Airborne Geophysical/Geological Mineral Inventory project funded by the Alaska State Legislature and managed by State of Alaska, Department of Natural Resources (DNR), Division of Geological & Geophysical Surveys (DGGS). The project seeks to catalyze private-sector mineral development investment. 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. This purpose for this publication is to compile and upgrade key digital data into a single publication for online data distribution.


How was the data set created?

  1. From what previous works were the data drawn?

    Akima, H., 1970 (source 1 of 21)
    Akima, H., 1970, A new method of interpolation and smooth curve fitting based on local procedures: Journal of the Association of Computing Machinery v. 7, no. 4, Association for Computing Machinery, New York, NY, USA.

    Type_of_Source_Media: paper
    Source_Contribution: total magnetic field data

    Burns, L.E. and Liss, S.A., 1998 (source 2 of 21)
    Burns, L.E., and Liss, S.A., 1998, Portfolio of aeromagnetic and resistivity maps of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Public Data File PDF 98-6, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 16 p., 1 sheet
    Type_of_Source_Media: digital data
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 3 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, 7200 Hz coplanar resistivity of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Public Data File PDF 98-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:63,360
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 63360
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 4 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, 7200 Hz coplanar resistivity of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Report of Investigation RI 98-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:63,360
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 63360
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 5 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, 900 Hz coplanar resistivity of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Public Data File PDF 98-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:63,360
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 63360
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 6 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, 900 Hz coplanar resistivity of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Report of Investigation RI 98-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:63,360
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 63360
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 7 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, CD-ROM containing gridded files and section lines of 1997 geophysical survey data for Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Public Data File PDF 98-8, 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: legacy data compilation

    DGGS Staff and others, 1998 (source 8 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, CD-ROM containing profile and gridded data and section lines of the 1997 geophysical survey data for Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Public Data File PDF 98-9, 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: legacy data compilation

    DGGS Staff and others, 1998 (source 9 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Flight lines of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Public Data File PDF 98-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:63,360
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 63360
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 10 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics and detailed electromagnetic anomalies of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska (part of C-4): Public Data File PDF 98-18B, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:31,680
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 31680
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 11 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics and detailed electromagnetic anomalies of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska (part of C-5): Public Data File PDF 98-18A, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:31,680
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 31680
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 12 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics and detailed electromagnetic anomalies of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska (parts of C-3 and C-4): Public Data File PDF 98-18C, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:31,680
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 31680
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 13 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics and electromagnetic anomalies of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska (clear diazo film version): Public Data File PDF 98-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:63,360
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 63360
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 14 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics and electromagnetic anomalies of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska (part of B-3 and B-4): Public Data File PDF 98-18G, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:31,680
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 31680
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 15 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics and electromagnetic anomalies of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska (part of B-4): Public Data File PDF 98-18F, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:31,680
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 31680
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 16 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics and electromagnetic anomalies of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska (part of B-5 and B-6): Public Data File PDF 98-18D, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:31,680
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 31680
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 17 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics and electromagnetic anomalies of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska (part of B-5): Public Data File PDF 98-18E, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:31,680
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 31680
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 18 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics and electromagnetic anomalies of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Public Data File PDF 98-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:63,360
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 63360
    Source_Contribution: legacy data compilation

    DGGS Staff and others, 1998 (source 19 of 21)
    Staff, DGGS, Dighem, and WGM, Inc., 1998, Total field magnetics of the Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Report of Investigation RI 98-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:63,360
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 63360
    Source_Contribution: legacy data compilation

    Fraser, D.C., 1978 (source 20 of 21)
    Fraser, D.C., 1978, Resistivity mapping with an airborne multicoil electromagnetic system: Geophysics v. 43, Society of Exploration Geophysicists, Tulsa, OK, United States.

    Type_of_Source_Media: paper
    Source_Contribution: raw and processed point data along flight lines

    Pritchard, R.A., 1998 (source 21 of 21)
    Pritchard, R.A., 1998, Project report of the 1997 geophysical survey data for Iron Creek area, Talkeetna Mountains Quadrangle, southcentral Alaska: Public Data File PDF 98-7, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 313 p., 2 sheets, scale 1:63,360
    Type_of_Source_Media: digital data
    Source_Scale_Denominator: 63360
    Source_Contribution: legacy data compilation

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

    Date: 1997 (process 1 of 12)
    Raw and processed point data along flight lines - These data are directly provided by the contractor. Raw data are a direct export from field collection instruments. Final data are processed by method according to the contractor provided reports and process steps in this document.

    Data sources used in this process:

    • Fraser, D.C., 1978

    Date: 1997 (process 2 of 12)
    Geophysical data - The geophysical data were acquired with a DIGHEM-V Electromagnetic (EM) system, a Scintrex cesium magnetometer, and a Herz VLF system installed in on AS350B-2 Squirrel helicopter. In addition, the survey recorded data from a radar altimeter, GPS navigation system, 50/60 Hz monitors and video camera.

    Date: 1997 (process 3 of 12)
    Total magnetic field data - The total magnetic field data were acquired with a sampling interval of 0.1 seconds, and were (1) corrected for diurnal variations by subtraction of the digitally recorded base station magnetic data, (2) leveled to the tie line data, and (3) interpolated onto a regular 100 m grid using a modified Akima (1970) technique. The regional variation (or IGRF gradient, 1995, updated to August, 1997) was removed from the leveled magnetic. The aeromagnetic data were interpolated onto a regular 100 m grid using a modified Akima (1970) technique. [Akima, H., 1970, A new method of interpolation and smooth curve fitting based on local procedures: Journal of the Association of Computing Machinery, v. 17, no. 4, p. 589-602.] The magnetic base station was a GSM-19T digital recording proton precession machine with a sensitivity of 0.20 nT and was sampled once every 3 seconds.

    Data sources used in this process:

    • Akima, H., 1970

    Date: 1997 (process 4 of 12)
    Inphase and quadrature components - The DIGHEM(V) EM system measured inphase and quadrature components at five frequencies. EM data were sampled at 0.1 second intervals. The EM inphase and quadrature data were drift corrected using base level data collected at high altitude (areas of no signal). Along-line filters were applied to the data to remove spheric spikes. The data were inspected for variations in phase, and a phase correction was applied to the data if necessary. Resistivities were then calculated from the inphase and quadrature data for all frequencies based on a pseudo-layer half-space model. Manual leveling of the inphase and quadrature of each coil pair, based on the resistivity data and comparisons to the data from the other frequencies, was performed. Automated micro-leveling was carried out in areas of low signal. The EM system responds to bedrock conductors, conductive overburden, and cultural sources. The power line monitors and the flight track video were examined to locate cultural sources. The EM anomalies that are indicated are classified by conductance. These anomalies are described in files 'ironcreek_emanomalies.csv' and 'ironcreek_projectreport.pdf.'

    Date: 1997 (process 5 of 12)
    Vector data in shape file format, examples: line path, data contours - These data were created by exporting data and interpretations to vector format.

    Date: 1998 (process 6 of 12)
    Project report, portfolio report, and other important documents - The project report, portfolio report, and other important documents were generated by the contractor, DGGS staff, or a combination.

    Date: 2014 (process 7 of 12)
    Legacy data compilation - DGGS staff compiled and organized previously published data and the originating data from the contractor. Print format maps of data in plotter file format were created by the contractor (1998) using data and interpretation products derived from the final ascii data. DGGS staff converted the hpp files into PDFs.

    Data sources used in this process:

    • Burns, L.E. and Liss, S.A., 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • DGGS Staff and others, 1998
    • Pritchard, R.A., 1998

    Date: 2014 (process 8 of 12)
    Data in Geosoft GDB format - These data were created by importing the final ascii data into Geosft Oasi Montaj v8.2 using the provided *.iO import file.

    Date: 2014 (process 9 of 12)
    Geographically registered gridded data in Geosft GRD format - These data were created by DGGS using the final ascii data. Geosft Oasis montaj v8.2 was used to create the grid files. 80 meter grid cell size and the minimum curvature operate were used in the production of these grids.

    Date: 2014 (process 10 of 12)
    Geographically registered gridded data in GeoTiff format - These data were created by DGGS using Geosft Oasis montaj v8.2. Geosoft grd files were displayed in Geosft and exported to GeoTiff. A matching colorbar for each grid was displayed in Geosoft and export as a GeoTiff.

    Date: 2014 (process 11 of 12)
    Google Earth KMZ files - Created Google Earth KMZ files from the Geosoft format gridded data using ESRI ArcMap 10.2.2.

    Date: 2015 (process 12 of 12)
    Boundary polygon - The boundary polygon was generated by loading the final line data in Geosoft Oasis montaj v8.4. No tie (control) line data were used in this process. The final magnetic data was 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 ERSI shapefile.

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

    Burns, L.E., CGG, and Fugro GeoServices, Inc., 2014, Wrangellia survey area: Airborne magnetic and electromagnetic data in line (point), grid, vector, and map formats, Talkeetna Mountains, Healy, and Mt. Hayes quadrangles, south-central Alaska: Geophysical Report GPR 2014-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 56 sheets, 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?

    EM Sensitivity: 0.06 ppm at 900 Hz, 0.10 ppm at 5,500 Hz,0.10 ppm at 7,200 Hz, 0.30 ppm at 56,000 Hz, EM and Magnetometer Sample rate: 10 per second, Magnetometer Sensitivity: 0.01 nT

  2. How accurate are the geographic locations?

    A Sercel Real-Time Differential Global Positioning System (RT-DGPS) was used for both navigation and flight path recovery. The helicopter position was derived every 0.5 seconds using real-time differential positioning to a relative accuracy of better than 10 m. Flight path positions were projected onto the Clark 1866 (UTM zone 6) spheroid, 1927 North American datum using a centraI meridian (CM) of 147 degrees, a north constant of 0 and an east constant of 500,000. Positional accuracy of the presented data is better than 10 m with respect to the UTM grid.

  3. How accurate are the heights or depths?

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

    Many of the files for this release were published on paper and available by mail order beginning in 1998. This updated data release provides a compilation of the previously published paper files (in PDF format) and the originating data files that were acquired from the contractor. We believe that this data release is complete, however, if additional or revised project files are found after the initial publication, these files will be added to the compilation. In addition, we have identified the following line data gaps. 393195 E 6905609 N; 300 meter along line data gap 422996 E 6939762 N; 500 meter along line data gap 423250 E 6940628 N; 500 meter along line data gap 386478 E 6913465 N; 300 meter along line data gap 416023 E 6937178 N; 600 to 680 meter between line distance 396127 E 6907233 N; 1000 meters of sparse data at south end of flight line Line number cannot be correlated to exact date of data acquisition until further documentation is recovered.

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

    Data originate from one company using the same contract specifications for all data.


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 2014-6

  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: 21-Dec-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:


Generated by mp version 2.9.21 on Mon Dec 21 09:36:10 2015