: Project Name: Bonnifield Contracting Agency: State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS) DGGS Section: Mineral Resources section Program: Alaska Airborne Geophysical/Geological Mineral Inventory Program Funding Source: Alaska State Legislature Contractor: Stevens Exploration Management Corp. Survey Flown By: Fugro Airborne Surveys Corp. now CGG (year 2015) Fugro Project Number: 6061 DGGS Contract Manager: Laurel E. Burns Data Acquisition: Digitally acquired Line miles (km): 2811.8 miles (4525.2 km) Data Acquisition: Start Date (YYYY-MM-DD): 2006-10-02 End Date (YYYY-MM-DD): 2007-02-02 Platform: Helicopter Platform: Model: AS-350-B3 turbine Survey Altitude Model: Mean terrain clearance (height above ground) Nominal Helicopter Height: 58 meters Nominal Bird Height: 30 meters Traverse: Line Azimuth: 0 degrees / 180 degrees Traverse: Line Spacing: 1/4 mile (400 meters) Tie: Line Azimuth: 90 degrees / 270 degrees Tie: Line Spacing: approximately 3 miles (approximately 4800 meters) Border lines: present around all non-parallel and non-perpendicular edges Magnetics: Magnetometer: Fugro D1344 processor with ScintrexCS3 sensor, mounted in bird Electromagnetics: Sensor Model: Dighem(V) Navigation System: Sensor: Novatel OEM4 Global Positioning System Navigation System: Method: Post-flight differential positioning Additional equipment: Radar and laser altimeters, video camera, and 50/60 Hz monitors : Operating frequencies used for the Dighem (V) system. : Atm2 orientation nominal actual and dipole moments separation 211 coaxial / 1000 Hz 1114 Hz 8 meters 211 coplanar / 900 Hz 916 Hz 8 meters 67 coaxial / 5500 Hz 5523 Hz 8 meters 56 coplanar / 7200 Hz 7026 Hz 8 meters 15 coplanar / 56,000 Hz 55840 Hz 8 meters : FLIGHT AND LINE NAMING : Example: L11020:29082 : L = L for transverse(production) T for tie(cross) 1 = Area 1 = Line number digit 1 0 = Line number digit 2 2 = Line number digit 3 0 = Reflight number : 2 = System number digit 1 9 = System number digit 2 0 = Flight number digit 1 8 = Flight number digit 2 2 = Flight number digit 3 : Example: T15021:3089 : T = T for tie(cross) L for transverse(production) 1 = Area 5 = Line number digit 1 0 = Line number digit 2 2 = Line number digit 3 1 = Reflight number : 3 = System number digit 1 0 = Flight number digit 1 8 = Flight number digit 2 9 = Flight number digit 3 : : We provide an index map showing the locations of the 1:63,360-scale map sheets that are included on this publication. Two sheets are needed to cover the area. Bounding coordinates for the sheets are given immediately below. The bounding coordinates of the gridded data differ from those of the individual map sheets. 1:63,360-scale maps, sheet 1 West, -148.83 1:63,360-scale maps, sheet 1 East, -147.92 1:63,360-scale maps, sheet 1 North, 64.17 1:63,360-scale maps, sheet 1 South, 63.83 1:63,360-scale maps, sheet 2 West, -147.92 1:63,360-scale maps, sheet 2 East, -147.00 1:63,360-scale maps, sheet 2 North, 64.17 1:63,360-scale maps, sheet 2 South, 63.83
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, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.
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.
The Alaska State Legislature provided funding for the 2007 geophysical data through the Alaska Geophysical/Geological Mineral Inventory Project, a Capital Improvement Project.
The Bonnifield 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 project seeks to catalyze private-sector mineral development investment. The project 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.
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.
Fugro Airborne Surveys Corp., Unpublished material, DVD containing original raw and processed data, and vector files for the Liberty Bell area, western Bonnifield mining district, central Alaska.
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Alaska Division of Geological & Geophysical Surveys, Fugro Airborne Surveys Corp., 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, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.
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, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.
Survey contracts specified the conditions and specifications under which these data were collected. Altimeter, heading, lag, and frequent EM calibrations were done. The magnetometer used had a sensitivity of 0.01 nT. Resistivity sensitivity varies among the different frequencies from 0.06 ppm to 0.30 ppm. More information will be available in the project report to be published in the future.
The helicopter position was derived every 0.5 seconds using post-flight differential positioning to a relative accuracy of better than 5 m. Positional accuracy of the presented data is better than 10 m with respect to the UTM grid. Further inaccuracies may be introduced by the interpolation and gridding process.
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 HMSL. 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 HMSL (or 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.
The file 'bonnifield_linedata.xyz' contains 2004937 records with 28 channels each. Channel names and definitions of all 28 channels are included in 'bonnifield_linedata_readme.txt'.
The DIGHEM V EM system measured inphase and quadrature components at five frequencies. Two vertical coaxial-coil pairs operated at 1114 (1000) and 5523 (5500) Hz while three horizontal coplanar-coil pairs operated at 916 (900), 7026 (7200), and 55,840 (56,000) Hz. The EM data were sampled at 0.1 second intervals. 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 total magnetic field data were acquired with a sampling interval of 0.1 seconds, and were (1) corrected for measured system lag, (2) corrected for diurnal variations by subtraction of the digitally recorded base station magnetic data (saved as tfmag in bonnifield_linedata.xyz), (3) adjusted for regional variations (or IGRF gradient, 2005, updated to November 2006) using altimeter adjusted IGRF, (4) leveled to the tie line data (saved as magigrf in bonnifield_linedata.xyz), and (5) interpolated onto a regular 80m grid using a modified Akima (1970) technique.
CHANNELS WITH MISSING VALUES IN 'bonnifield_linedata.xyz' Channel Data Null Values Values
***************************************** : x 4,009,874 0 : y 4,009,874 0 : FID 4,009,846 28 : latitude 4,009,874 0 : longitude 4,009,874 0 : flight 4,009,846 28 : altbird 4,009,846 28 : dem 4,009,866 8 : magigrf 4,008,806 1,068 : tfmag 4,008,814 1,060 : cpi900 4,009,658 216 : cpq900 4,009,658 216 : cxi1000 4,009,658 216 : cxq1000 4,009,658 216 : cxi5500 4,009,658 216 : cxq5500 4,009,658 216 : cpi7200 4,009,858 16 : cpq7200 4,009,858 16 : cpi56k 4,009,658 216 : cpq56k 4,009,658 216 : res900 4,008,450 1,424 : DEP900 3,718,652 291,222 : RES7200 4,008,578 1,296 : DEP7200 3,938,644 71,230 : RES56K 4,007,892 1,982 : DEP56K 3,987,350 22,524 : DIFI 4,009,658 216 : DIFQ 4,009,658 216Missing magnetic values occur in the Bonnifield database for the typical reasons of the lagging process, at the beginning of some lines, and due to despiking. The Bonnifield data has a number of magnetic dropouts. When the missing interval is too wide to comfortably interpolate, the area is left as dummies in the database. When the profile gaps are extensive enough, the gridding does not spline across them.
Data for this survey were collected by a single subcontractor (Fugro Airborne Surveys) who was responsible for collecting and processing the data. All the data were collected with the same instruments (magnetometers, electromagnetic bird and sensors, gamma ray spectrometer, altimeters, and navigational system).
Are there legal restrictions on access or use of the data?
- 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).
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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.
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|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|