Vibracore CT scans from the San Lorenzo River

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Frequently anticipated questions:

What does this data set describe?

Title: Vibracore CT scans from the San Lorenzo River
This data release contains information on computed tomography (CT) images of a vibracore that was collected by the U.S. Geological Survey in 2019. A site next to the San Lorenzo River in Henry Cowell Redwoods State Park, California, was cored to understand the history of recent vertical incision and floodplain abandonment. The core was split into 3 segments after collection. Each segment was scanned using a Geotek Rotating X-ray CT (RXCT) System and CT reconstruction was performed using Geotek reconstruction software. Geotek CT_Quickview software was used to select a representative down-core orthogonal slice from each core segment and the Geotek AddRuler software was used to display core-lengths in each image. The downcore orthogonal slice CT images of each core segment are included as three separate TIFF files. Each TIFF file is accompanied by a software-proprietary XML file that contains the x-ray scanning configuration and settings in addition to dimensional data of the TIFF images.
Additional information about the field activity from which these data were derived is available online at:
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?
    Nasr, Brandon M., Selle, SeanPaul La, Chapman, William A.L., and Finnegan, Noah J., 20210604, Vibracore CT scans from the San Lorenzo River: data release DOI:10.5066/P9ZT7ZOX, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.07063
    East_Bounding_Coordinate: -122.07063
    North_Bounding_Coordinate: 37.04239
    South_Bounding_Coordinate: 37.04239
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 05-Nov-2019
    Ground condition at the time the vibracore was collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: TIFF
  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 (1)
    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 NAD83.
      The ellipsoid used is GRS 1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
  7. How does the data set describe geographic features?
    Zip file contains 3 TIFF files and their respective software-proprietary XML files. (Source: Producer defined)
    SL-19-02A_R, SL-19-02B_R, SL-19-02C_R
    CT Core images with the following attributes from the Geotek software-proprietary XML files:
    Image-Type= Orthogonal View
    Core ID= SL-19-02
    Section-number= A (B and C are not listed here)
    Physical Width= 9.10
    Physical Height= 110.03
    Physical Top= 1700.01
    Pixels per CM= 104
    Horizontal resolution= 104 pixels
    Pixel width= 946
    Scan Lines= 11473
    Detector gear ration= 462:1
    Camera Name= Thermo Kevex PSX10-65W
    Average= 1
    Filename= SL-19-02A_R, SL-19-02B_R, SL-19-02C_R
    X-ray Voltage= 130
    X-ray Current= 209.8
    X-ray spot size= 38
    Source object distance= 221.73
    Source detector distance= 575.01
    Detector CCD mode= 2x2
    Enabled= False
    Window Count= 2
    Window= 400
    SigmaA= 0.1
    SigmaV= 0.0005
    Weight= 0.4
    Window= 100
    SigmaA= 0.1
    SigmaV= 0.0005
    Weight= 1
    Reduction= 0.85
    (Source: producer defined)
    Range of values

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Brandon M. Nasr
    • SeanPaul La Selle
    • William A.L. Chapman
    • Noah J. Finnegan
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)

Why was the data set created?

This dataset was collected to better understand the vertical incision and floodplain abandonment in the San Lorenzo 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: 2019 (process 1 of 3)
    A vibracore was collected on November 05, 2019. A handheld global satellite navigation system (GNSS) receiver was used to determine the coordinates of the vibracore site. 76.2 mm OD (outer diameter) aluminum irrigation pipe with 1.27 mm wall thickness (inner diameter is 73.66 mm) was driven into the sediment to capture the stratigraphy. A concrete vibrator head attached to the aluminum pipe, which was powered by a Honda GX160~5 HP 4 stroke (modified by Northrock) was used to drive the pipe into the sediment. The pipe was extracted using a winch attached to a steel tripod. Due to difficulty penetrating through dry silt and sand, the borehole was reoccupied twice, resulting in three core segments (A,B,C).
    Date: 07-Nov-2019 (process 2 of 3)
    The core segments were brought to the USGS Pacific Coastal and Marine Science Center core facility, where they were split into archive halves and working halves. The working halves' internal structures were imaged with a Geotek Rotating X-Ray CT scanner. Rotational images were acquired every 0.2 degrees at 130 kilovolts (kV) and 210 microamperes, and the rotational images were reconstructed by GeoTek's Reconstructor Software. Once reconstructed, the files were imported into GeoTek's Image Viewer software and a representative downcore slice image was chosen. A ruler was added to the TIFF images using the GeoTek Add Ruler software, which exported the final TIFF and software-proprietary XML files, adding 'R' to the file name. The rulers on the TIFF images denote the length of each core segment, not the depths at which the cores were collected.
    Date: 10-Jun-2021 (process 3 of 3)
    Corrected the URL link to the USGS Field Activity listed in the Supplemental Information section. No data were changed. (
  3. What similar or related data should the user be aware of?

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

  1. How well have the observations been checked?
    No formal attribute accuracy tests were conducted.
  2. How accurate are the geographic locations?
    The location of the sample was determined using a Garmin eTrex 30x handheld global satellite navigation system (GNSS) receiver capable of receiving wide area augmentation system (WAAS) signals. The manufacturer reported accuracy for horizontal position is 3-5 m while receiving WAAS signals.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    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.
  5. How consistent are the relationships among the observations, including topology?
    The rulers on the TIFF images denote the length of each core segment, not the depths at which the cores were collected.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
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 and The University of California Santa Cruz as the originator(s) of the dataset and in products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? These data are available as TIFF images along with their software-proprietary XML files contained in a single zip file ( and are accompanied by 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?
  5. What hardware or software do I need in order to use the data set?
    The zip file contains raster data in TIFF format, which can be opened with most graphics and image editing software.

Who wrote the metadata?

Last modified: 10-Jun-2021
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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