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/2 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.
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:
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.
This project was funded by the State of Alaska's Airborne Geophysical/Geological Mineral Inventory (AGGMI) program.
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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.
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:
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:
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:
Data sources used in this process:
Data sources used in this process:
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:
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:
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>
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.
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.
This publication release provides the entire dataset generated by this project.
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.
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.
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GPR 2018-10
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.
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.
| 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 |
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| Network links: |
<http://doi.org/10.14509/29690> |
(907)451-5020 (voice)
(907)451-5050 (FAX)
dggspubs@alaska.gov