Detailed aeromagnetic survey point data of the Trinidad Area, California

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Frequently anticipated questions:

What does this data set describe?

Title:
Detailed aeromagnetic survey point data of the Trinidad Area, California
Abstract:
This data release provides access to point measurement data from a low-altitude, aeromagnetic survey of a part of northwestern California. The survey extends west of the Klamath Mountains across the Pacific Ocean coastline over the continental shelf and covers the towns of Crescent City, Trinidad, Fortuna, Eureka, Arcata, and McKinleyville. Data were acquired during the summer and fall of 2024 by Xcalibur Multiphysics working under contract to the Yurok Tribe and under supervision of the U.S. Geological Survey. Total magnetic field values were acquired using a fixed-wing aircraft flown at a target elevation of 305 meters (m) above terrain and along flight lines and tie lines spaced 600 m and 6000 m apart, respectively. Flight lines were directed northeast-southwest; tie lines were directed northwest-southeast. A total of 13,134 line-kilometers were acquired.
Supplemental_Information:
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    Watt, Janet T., Langenheim, Victoria E., and Staisch, Lydia M., 20250403, Detailed aeromagnetic survey point data of the Trinidad Area, California: data release DOI:10.5066/P13SZBH7, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Watt, Janet T., Langenheim, Victoria E., and Staisch, Lydia M., 2025, Detailed Aeromagnetic Survey of the Trinidad Area, California: data release DOI:10.5066/P13SZBH7, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Watt, J.T., Langenheim, V.E., and Staisch, L.M., 2025, Detailed aeromagnetic survey of the Trinidad Area, California: U.S. Geological Survey data release, https://doi.org/10.5066/P13SZBH7.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -124.5260
    East_Bounding_Coordinate: -123.7210
    North_Bounding_Coordinate: 41.9360
    South_Bounding_Coordinate: 40.5660
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 28-Aug-2024
    Ending_Date: 27-Sep-2024
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: comma-delimited text
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (3337738)
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.00001. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is World Geodetic System 1984 (WGS 84).
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: mean sea level
      Altitude_Resolution: 5
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    Trinidad_aeromag.csv
    table containing attribute information associated with magnetic data set (Source: Producer defined)
    date
    Flight date (Source: Producer defined)
    Range of values
    Minimum:20240828
    Maximum:20240927
    Units:YYYYMMDD Universal Time Coordinated (UTC)
    diurnal
    Diurnal correction (Source: Producer defined)
    Range of values
    Minimum:-51.232
    Maximum:36.260
    Units:nanotesla
    dtm
    Digital terrain model elevation (3DEP), referenced to mean sea level (meters) (Source: Producer defined)
    Range of values
    Minimum:0.000
    Maximum:1322.869
    Units:meter
    easting_WGS84
    Easting value (UTM10N, WGS84) (Source: Producer defined)
    Range of values
    Minimum:370620.554
    Maximum:439773.354
    Units:meter
    fid
    Fiducial (seconds since midnight) (Source: Producer defined)
    Range of values
    Minimum:55334.05
    Maximum:94504.20
    Units:Seconds since beginning of UTC day at start of line
    flight
    Flight number (Source: Producer defined)
    Range of values
    Minimum:9
    Maximum:23
    Units:integer
    Flux_X
    Fluxgate magnetometer X component value (Source: Producer defined)
    Range of values
    Minimum:-48701.734
    Maximum:-29421.870
    Units:nanotesla
    Flux_Y
    Fluxgate magnetometer Y component value (Source: Producer defined)
    Range of values
    Minimum:-25681.289
    Maximum:27615.556
    Units:nanotesla
    Flux_Z
    Fluxgate magnetometer Z component value (Source: Producer defined)
    Range of values
    Minimum:-37331.591
    Maximum:31020.602
    Units:nanotesla
    gpsz
    Aircraft GPS elevation, referenced to mean sea level (meters) (Source: Producer defined)
    Range of values
    Minimum:238.830
    Maximum:1607.430
    Units:meter
    height
    Aircraft height above above surface from digital elevation model (Source: Producer defined)
    Range of values
    Minimum:191.915
    Maximum:1322.758
    Units:meter
    igrf
    International geomagnetic reference field (IGRF) value (Source: Producer defined)
    Range of values
    Minimum:48766.773
    Maximum:49602.675
    Units:nanotesla
    latitude_WGS84
    Aircraft latitude value in WGS84 (Source: Producer defined)
    Range of values
    Minimum:40.56619
    Maximum:41.93837
    Units:degrees
    line
    Flight line number (Source: Producer defined)
    Range of values
    Minimum:10010
    Maximum:90210
    Units:integer
    longitude_WGS84
    Aircraft longitude value in WGS84 (Source: Producer defined)
    Range of values
    Minimum:-124.52850
    Maximum:-123.71929
    Units:degrees
    mag_comp
    Compensated total magnetic field value (Source: Producer defined)
    Range of values
    Minimum:48708.471
    Maximum:50757.584
    Units:nanotesla
    mag_diu
    Diurnal and lag corrected total magnetic field value (Source: Producer defined)
    Range of values
    Minimum:48697.039
    Maximum:50772.720
    Units:nanotesla
    mag_raw
    Uncompensated total magnetic field value (Source: Producer defined)
    Range of values
    Minimum:48698.268
    Maximum:50741.332
    Units:nanotesla
    mag_rmi
    Final residual magnetic intensity value (Source: Producer defined)
    Range of values
    Minimum:-410.827
    Maximum:1333.362
    Units:nanotesla
    mag_tmi
    Final total magnetic intensity value (Source: Producer defined)
    Range of values
    Minimum:48696.157
    Maximum:50781.935
    Units:nanotesla
    northing_WGS84
    Aircraft northing value (UTM10N, WGS84) (Source: Producer defined)
    Range of values
    Minimum:4491493.189
    Maximum:4643535.896
    Units:meter
    time_ssm
    Elapsed time in seconds since midnight (Source: Producer defined)
    Range of values
    Minimum:0.00
    Maximum:86399.90
    Units:seconds
    Entity_and_Attribute_Overview:
    The data in this release are as provided to the USGS by the contractor, Xcalibur Multiphysics. The file trinidad_aeromag.csv provides point measurements along each flight line and tie line in comma-separated-value (CSV) format. Additional information is available in the accompanying document 2400075_YurokTribe_Tech_Report_508.pdf.
    Entity_and_Attribute_Detail_Citation:
    Airborne survey procedures, quality control, and data processing methods are described in the document 2400075_YurokTribe_Tech_Report_508.pdf, provided by the contractor. Point data are available in the file Trinidad_aeromag.csv provided by the contractor and in CSV format.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Janet T. Watt
    • Victoria E. Langenheim
    • Lydia M. Staisch
  2. Who also contributed to the data set?
    The Trinidad aeromagnetic survey was conducted by Xcalibur Multiphysics, working under contract with the Yurok Tribe and under supervision of the U.S. Geological Survey. David Miles was project manager and data processing was done by Fabian Linares and Tonia Bojkova. The Yurok Tribe coordinated flight and access permissions.
  3. To whom should users address questions about the data?
    PCMSC Science Data Coordinator
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA
    US

    831-427-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

These data were acquired to support earthquake hazard investigations and geologic mapping of the greater Trinidad area of northwestern California. The primary focus was to map continuity and geometry of faults and folds from the town of Fortuna north to Smith River.

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: 01-Nov-2024 (process 1 of 2)
    While in the field, the base-station magnetometers located in McKinleyville were monitored for magnetic field variations in excess of contract specifications. In the airborne magnetics, a fourth difference was calculated on the compensated total magnetic field in order to verify noise level and identify and remove discrete spikes. Data were corrected for the lag in time between the onboard GPS system and the tail-mounted magnetometer. Uncompensated and compensated total magnetic field profiles were monitored on a daily basis to assess compensation effectiveness. Readings from the two base stations were used to calculate and remove diurnal variations. Please see contractor report (2400075_YurokTribe_Tech_Report_508.pdf) for additional details. Person who carried out this activity:
    Janet T. Watt
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Research Geophysicist
    2885 Mission Street
    Santa Cruz, CA
    US

    831-460-7565 (voice)
    jwatt@usgs.gov
    Date: 01-Nov-2024 (process 2 of 2)
    Flight and tie lines were "levelled" using the statistical distribution of total field differences at each flight-line-tie-line crossing. The goal was to obtain the smoothest possible correction model for each line that minimizes the difference in magnetic field measured at each tie-line-flight-line crossing. Finally, the full International Geomagnetic Reference Field (IGRF, Alken and others, 2021), updated to the date of the survey, was subtracted from the measured, corrected total magnetic intensity, thus providing the residual magnetic intensity.
  3. What similar or related data should the user be aware of?
    Alken, P., Thébault, E., Beggan, C.D., Amit, H., Aubert, J., Baerenzung, J., Bondar, T.N., Brown, W.J., Califf, S., Chambodut, A., Chulliat, A., Cox, G.A., Finlay, C.C., Fournier, A., Gillet, N., Grayver, A., Hammer, M.D., Holschneider, M., Huder, L., Hulot, G., Jager, T., Kloss, C., Korte, M., Kuang, W., Kuvshinov, A., Langlais, B., Léger, J.-M., Lesur, V., Livermore, P.W., Lowes, F.J., Macmillan, S., Magnes, W., Mandea, M., Marsal, S., Matzka, J., Metman, M.C., Minami, T., Morschhauser, A., Mound, J.E., Nair, M., Nakano, S., Olsen, N., Pavón-Carrasco, F.J., Petrov, V.G., Ropp, G., Rother, M., Sabaka, T.J., Sanchez, S., Saturnino, D., Schnepf, N.R., Shen, X., Stolle, C., Tangborn, A., Tøffner-Clausen, L., Toh, H., Torta, J.M., Varner, J., Vervelidou, F., Vigneron, P., Wardinski, I., Wicht, J., Woods, A., Yang, Y., Zeren, Z., and Zhou, B., 2021, International Geomagnetic Reference Field: the thirteenth generation.

    Online Links:

    Other_Citation_Details:
    Alken, P., Thébault, E., Beggan, C. D., Amit, H., Aubert, J., Baerenzung, J., Bondar, T. N., Brown, W. J., Califf, S., Chambodut, A., Chulliat, A., Cox, G. A., Finlay, C. C., Fournier, A., Gillet, N., Grayver, A., Hammer, M. D., Holschneider, M., Huder, L., Hulot, G., Jager, T., Kloss, C., Korte, M., Kuang, W., Kuvshinov, A., Langlais, B., Léger, J.-M., Lesur, V., Livermore, P. W., Lowes, F. J., Macmillan, S., Magnes, W., Mandea, M., Marsal, S., Matzka, J., Metman, M. C., Minami, T., Morschhauser, A., Mound, J. E., Nair, M., Nakano, S., Olsen, N., Pavón-Carrasco, F. J., Petrov, V. G., Ropp, G., Rother, M., Sabaka, T. J., Sanchez, S., Saturnino, D., Schnepf, N. R., Shen, X., Stolle, C., Tangborn, A., Tøffner-Clausen, L., Toh, H., Torta, J. M., Varner, J., Vervelidou, F., Vigneron, P., Wardinski, I., Wicht, J., Woods, A., Yang, Y., Zeren, Z., and Zhou, B., 2021, International Geomagnetic Reference Field: the thirteenth generation: Earth, Planets and Space, v. 73, n. 49, https://doi.org/10.1186/s40623-020-01288-x

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

  1. How well have the observations been checked?
    Magnetic field values were measured with a Scintrex CS-3 cesium-vapor magnetometer, with a resolution of 0.002 nanotesla (nT). Total magnetic field values were measured at 0.05-sec intervals. Magnetic signals caused by aircraft motion and heading were compensated using a Billingsley TMF 100 Triaxial (X,Y,Z) fluxgate magnetometer mounted in the tail stinger. Prior to the survey, the aircraft and its instrumentation were put through a series of roll, pitch, and yaw maneuvers to form a model of the aircraft's magnetic characteristics. These maneuvers were performed in a region of low magnetic gradient and high altitude to minimize influence of magnetic geologic sources and to develop a compensation correction for the survey data. Two stationary magnetometers were deployed within the survey area at McKinleyville to monitor and subsequently correct for diurnal magnetic field and magnetic storm variations. The base magnetometers were GEM Systems magnetometers sampled at 1-sec intervals. Navigation was accomplished with a GPS system mounted on the tail of the aircraft. The NovAtel Model OEMV-2 receiver has a real-time accuracy of 1.5 meters (L1), sampled at 0.5-sec intervals.
  2. How accurate are the geographic locations?
    Three-dimensional positions were determined with ta NovAtel OEMV-2 receiver with an antenna mounted on the tail of the aircraft. Realtime accuracy is estimated to be 1.5 m.
  3. How accurate are the heights or depths?
    Altitude was determined with the same GPS systems and a Bendix King KRA 10 radar altimeter. Altitude accuracy is estimated to be within 2 to 3 m.
  4. Where are the gaps in the data? What is missing?
    This data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    This dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints. Please see 'Distribution Info' for details.
Use_Constraints USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data. Users are advised to read the data set's metadata thoroughly to understand appropriate use and data limitations.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - CMGDS
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov
  2. What's the catalog number I need to order this data set? These data are available in csv format (Trinidad_aeromag.csv) accompanied by CSDGM FGDC-compliant metadata
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: File contains table in .csv format in format comma-delimited text (version Notepad, 11.2412.16.0) Size: 856.1
      Network links: https://doi.org/10.5066/P13SZBH7
    • Cost to order the data: None

  5. What hardware or software do I need in order to use the data set?
    Data can be viewed with any text reader software.

Who wrote the metadata?

Dates:
Last modified: 03-Apr-2025
Metadata author:
PCMSC Science Data Coordinator
U.S. Geological Survey, Pacific Coastal and Marine Science Center
2885 Mission Street
Santa Cruz, CA
US

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
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