Pilgrim Hot Springs airborne electromagnetic survey, Seward Peninsula, Alaska

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Frequently anticipated questions:


What does this data set describe?

Title:
Pilgrim Hot Springs airborne electromagnetic survey, Seward Peninsula, Alaska
Abstract:
Pilgrim Hot Springs airborne electromagnetic survey, Seward Peninsula, Alaska, Geophysical Report 2025-1, covers a portion of the Southwest corner of the Bendeleben quadrangle, north-northeast of Nome, Alaska. The survey was conducted to characterize subsurface electrical resistivity variations, supporting interpretations of hydrothermal circulation, fluid pathways, and near-surface thaw zones. The resulting dataset provides insights into the geologic framework and supports geothermal exploration by enabling evaluation of subsurface conditions, identification of energy prospects, and guidance for future drilling. Time-domain electromagnetic data were acquired using the helicopter-mounted SkyTEM 306HP system on September 8-9, 2023, by SkyTEM Canada Incorporated. A total of 73.2 line-kilometers were flown over a single survey block measuring 10.7 square kilometers. The block was flown with north-south line orientation and a nominal spacing of 100 meters, reduced to 50 meters near the center. Mean ground clearance was 35.8 +/- 15.7 meters, with a nominal survey speed of 101.4 +/- 7.8 km/hr. Data were inverted using Aarhus Workbench EM software to produce two subsurface resistivity models. SkyTEM Canada Incorporated generated a preliminary model from a laterally constrained inversion (referred to in the data files as skytem_lci), which applies only along-track constraints. Aqua Geo Frameworks produced a spatially constrained inversion model (referred to in the data files as agf_sci), which incorporates both along-track and cross-track constraints. The Aqua Geo Frameworks model is recommended for end-users, as it resolves finer-scale structures, including layering in the near-surface thaw zone. We also provide a 3D voxel dataset registered to elevation rather than raw depth for the model. These data are provided as a Geophysical Report under an open end-user license and are available on the DGGS website https://doi.org/10.14509/31452.
Supplemental_Information:
ascii_data:    ASCII format line data, other ASCII data	
databases_geosoft:    Geosoft format database of final line data, other Geosoft format databases	
documents:    Project report, calibration reports	
grids_geosoft:    Oasis montaj Geosoft GRD format gridded data	
grids_tif:    Geographically registered data value rasters of gridded data, GeoTiff format	
kmz:    Keyhole Markup Language (KML) kmz archive files of project data. Viewable on Google Earth and other compatible programs	
maps_pdf_format:    Printable and geographically registered maps in pdf format. Compatible with mobile device navigation and desktop mapping applications.	
models_resistivity:    Files for model input parameters as well as model outputs from Aarhus Workbench. Images of resistivity sections	
vector_data:    Line path and survey boundary in Esri shapefile (shp) format
  1. How might this data set be cited?
    Petersen, E.I., Fusso, L.A., Emond, A.M., Incorporated, SkyTEM Canada, Frameworks, Aqua Geo LLC, and Eichelberger, J.C., 2025, Pilgrim Hot Springs airborne electromagnetic survey, Seward Peninsula, Alaska: Geophysical Report GPR 2025-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 7 p
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -164.954182
    East_Bounding_Coordinate: -164.903457
    North_Bounding_Coordinate: 65.109621
    South_Bounding_Coordinate: 65.016508
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2025
    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?
      This is a raster 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: 3
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -165
      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 WGS84.
      The ellipsoid used is WGS 84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257223563.
  7. How does the data set describe geographic features?
    ascii_data
    ASCII format line data, other ASCII data (Source: SkyTEM Canada Incorporated and Aqua Geo Frameworks LLC)
    databases_geosoft
    Geosoft format database of final line data, other Geosoft format databases (Source: SkyTEM Canada Incorporated and Aqua Geo Frameworks LLC)
    documents
    Project report, calibration reports (Source: SkyTEM Canada Incorporated and Aqua Geo Frameworks LLC and Alaska Division of Geological & Geophysical Surveys (DGGS))
    grids_geosoft
    Oasis montaj Geosoft GRD format gridded data (Source: SkyTEM Canada Incorporated and Aqua Geo Frameworks LLC and Alaska Division of Geological & Geophysical Surveys (DGGS))
    grids_tif
    Geographically registered data value rasters of gridded data, GeoTiff format (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))
    kmz
    Keyhole Markup Language (KML) kmz archive files of project data. Viewable on Google Earth and other compatible programs (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))
    maps_pdf_format
    Printable and geographically registered maps in pdf format. Compatible with mobile device navigation and desktop mapping applications. (Source: SkyTEM Canada Incorporated and Aqua Geo Frameworks LLC)
    models_resistivity
    Files for model input parameters as well as model outputs from Aarhus Workbench. Images of resistivity sections (Source: SkyTEM Canada Incorporated and Aqua Geo Frameworks LLC)
    vector_data
    Line path and survey boundary in Esri shapefile (shp) format (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

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?
    This work was supported by the State of Alaska capital improvement project funds. DGGS thanks the United States Geological Survey for assistance with data quality control. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the U.S. Geological Survey. Mention of trade names or commercial products does not constitute their endorsement by the U.S. Geological Survey.
  3. To whom should users address questions about the data?
    Alaska Division of Geological & Geophysical Surveys
    GIS Manager
    3354 College Rd
    Fairbanks, AK
    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 Pilgrim Hot Springs airborne electromagnetic survey was conducted to characterize subsurface electrical resistivity variations, providing critical information on hydrothermal circulation, fluid pathways, and near‑surface thaw zones. The resulting dataset strengthens Alaska's ability to evaluate geothermal resources by improving understanding of subsurface conditions and informing decisions about future drilling. These insights support long‑term energy planning, reduce exploration risk, and help advance locally available, low‑carbon energy options for Alaskan communities.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2025 (process 1 of 2)
    Data acquisition - SkyTEM Canada Incorporated acquired time‑domain electromagnetic data using the helicopter‑mounted SkyTEM 306HP system on September 8-9, 2023, flying 73.2 line‑kilometers over a single 10.7‑square‑kilometer survey block. The crew flew the block along north-south lines with a nominal spacing of 100 meters, tightening the spacing to 50 meters near the center. They maintained a mean ground clearance of 35.8 +/- 15.7 meters and a nominal survey speed of 101.4 +/- 7.8 km/hr. DGGS contractors used Aarhus Workbench EM software to invert the data and generate two subsurface resistivity models. SkyTEM Canada Incorporated produced a preliminary model using a laterally constrained inversion (skytem_lci), which applies only along‑track constraints. Aqua Geo Frameworks generated a spatially constrained inversion model (agf_sci) that incorporates both along‑track and cross‑track constraints.
    Date: 2025 (process 2 of 2)
    Data cataloged for archival and publication - Final data were published and archived by DGGS.
  3. What similar or related data should the user be aware of?
    Staff, DGGS, 2019, Geothermal Resources of Alaska: Digital Data Series DDS 16, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Emond, A.M., and Daanen, R.P., 2020, Pilgrim Hot Springs CSAMT measurements, Seward Peninsula, Alaska: Raw Data File RDF 2020-9, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 5 p
    Motyka, R.J., Moorman, M.A., and Liss, S.A., 1983, Geothermal resources of Alaska: Miscellaneous Publication MP 8, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:2,500,000

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 the 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?
    Station coordinates were positioned using a real-time or post-processed corrected differential GPS.
  3. How accurate are the heights or depths?
    Not applicable
  4. Where are the gaps in the data? What is missing?
    The dataset provides processed geophysical and positional data for the entire survey extent.
  5. How consistent are the relationships among the observations, including topology?
    Data were supplied by providers in accordance with DGGS contract requirements (see accompanying project report). 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)
    State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys
    3354 College Road
    Fairbanks, AK
    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 2025-1
  3. What legal disclaimers am I supposed to read?
    The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services 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, any failure thereof, or otherwise, and 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: 18-Dec-2025
Metadata author:
Simone Montayne
3354 College Road
Fairbanks, AK
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 2.9.50 on Thu Dec 18 17:02:50 2025