Water column acoustic backscatter data from the mouth of the Columbia River, Oregon and Washington, 2013

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Frequently anticipated questions:


What does this data set describe?

Title:
Water column acoustic backscatter data from the mouth of the Columbia River, Oregon and Washington, 2013
Abstract:
Spatial surveys of water column acoustic backscatter were performed between May 28 and June 2, 2013, in the mouth of the Columbia River, Oregon and Washington. These data were collected using a Biosonics DTX single-beam echosounder with 430 kHz transducer.
Supplemental_Information:
Information about the data collection field activities can be found at: https://cmgds.marine.usgs.gov/fan_info.php?fan=S0313WO
  1. How might this data set be cited?
    Stevens, Andrew W., Gelfenbaum, Guy, MacMahan, Jamie, Reniers, Ad J.H.M., Elias, Edwin P., Sherwood, Christopher R., and Carlson, Emily M., 2017, Water column acoustic backscatter data from the mouth of the Columbia River, Oregon and Washington, 2013: data release DOI:10.5066/F7NG4NS1, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Stevens, Andrew W., Gelfenbaum, Guy, MacMahan, Jamie, Reniers, Ad J.H.M., Elias, Edwin P., Sherwood, Christopher R., and Carlson, Emily M., 2017, Oceanographic measurements and hydrodynamic modeling of the mouth of the Columbia River, Oregon and Washington, 2013: data release DOI:10.5066/F7NG4NS1, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -124.029598
    East_Bounding_Coordinate: -123.987173
    North_Bounding_Coordinate: 46.267905
    South_Bounding_Coordinate: 46.238508
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/590b751ce4b0e541a0378cba?name=mcr13_biosonics_map.png&allowOpen=true (PNG)
    Map showing locations of survey transects
    https://www.sciencebase.gov/catalog/file/get/590b751ce4b0e541a0378cba?name=mcr13_biosonics_ex.png&allowOpen=true (PNG)
    Image showing water column backscatter data from one of the transects surveyed at three different stages of the tide cycle
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 28-May-2013
    Ending_Date: 02-Jun-2013
    Currentness_Reference:
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: NetCDF files
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference:
      Data were collected continuously along survey transects. Refer to self-contained NetCDF files for more location information.
    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 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is D_WGS_1984.
      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.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    NetCDF files are self-contained and attribute information may be found in the header of the file itself.
    Entity_and_Attribute_Detail_Citation:
    The entity and attribute information was generated by the individual and/or agency identified as the originator of the data set. Please review the rest of the metadata record for additional details and information.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Andrew W. Stevens
    • Guy Gelfenbaum
    • Jamie MacMahan
    • Ad J.H.M. Reniers
    • Edwin P. Elias
    • Christopher R. Sherwood
    • Emily M. Carlson
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Andrew W. Stevens
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Oceanographer
    2885 Mission Street
    Santa Cruz, CA
    USA

    831-460-7424 (voice)
    831-427-4748 (FAX)
    astevens@usgs.gov

Why was the data set created?

These water column acoustic backscatter data were collected as a part of a larger investigation into hydrodynamics in the mouth of the Columbia River, Oregon and Washington.

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: 02-Jun-2013 (process 1 of 2)
    A total of 62 km of tracklines were surveyed with a Biosonics single-beam echosounder in the mouth of the Columbia River (MCR) between May 28 and June 2, 2013. Several cross-channel transects were surveyed repeatedly to characterize changes in water column acoustic backscatter amplitude at different stages of the tide cycle. Measurements of acoustic backscatter amplitude in the water column were collected using a Biosonics single-beam echosounder with a 430 kHz transducer pole-mounted to the R/V Park Snavely. A Trimble R7 global navigation satellite system (GNSS) receiver and Trimble Zephyr Model 2 GNSS antenna was used to provide positioning during the surveys. Real-time differential corrections from the Washington State Reference Network (http://www.wsrn3.org/) were applied to achieve survey-grade horizontal and vertical GNSS positions while the vessel was underway. Biosonics Visual Acquisition software (version 6.1.0.7382) was used for data acquisition and merging of the acoustic and positioning data. Raw backscatter data from each ping were digitized with an analog to digital converter in the echosounder at a rate of 41667 Hz, resulting in a profile of acoustic backscatter counts versus depth at intervals of 1.8 cm. Raw counts of acoustic backscatter were converted to target strength assuming a seawater absorption coefficient of 0.085 dB/m, a source level of 216 dB re 1 microPa m, and receiver sensitivity of -61.4 dB/count derived from calibrations performed in a test tank by the manufacturer.
    Date: 14-Jan-2016 (process 2 of 2)
    Data were accumulated into NetCDF files.
  3. What similar or related data should the user be aware of?
    International Hydrographic Organization (IHO), 2008, IHO standards for hydrographic surveys (5th ed.): International Hydrographic Bureau Special Publication 44, 28p., Monaco.

    Online Links:


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?
    Manufacturer reported accuracy for the differentially corrected horizontal positions for the Trimble R7 rover trajectories is 0.8 cm + 0.5 ppm. Baselines from the GNSS base station were typically less than 5 km, suggesting a horizontal accuracy of survey-vessel positions to be 0.825 cm.
  3. How accurate are the heights or depths?
    Manufacturer reported accuracy for the differentially corrected vertical positions for the Trimble R7 rover trajectories is 1.5 cm + 1 ppm. Baselines from the GNSS base station were typically less than 5 km, suggesting the vertical accuracy of survey vessel positions to be 2 cm relative to the base station coordinate. Additional uncertainty in the final computed elevations data is related to unmeasured variability in the speed of sound used to compute depths from bathymetric soundings and, thus, are depth-dependent. Based on analysis of all available speed of sound measurements, we estimate uncertainties in the final depth soundings to be 1 percent of the water depth. The total vertical uncertainty is calculated using Equation 1: sigmat=sqrt(a^2+(b×d)^2), where sigmat is the total vertical uncertainty, a is the uncertainty of the GNSS vertical position, b is the depth-dependent uncertainty factor (0.01), and d is water depth (International Hydrographic Organization, 2008). Maximum water depths surveyed on this mapping mission are approximately 35 m yielding a maximum total vertical uncertainty of 37 cm. Uncertainty in the vertical positions associated with pitch and roll of the survey vessels is unknown.
  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 metadata for each part of this data release carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    Data fall within expected ranges.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: none
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.
  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
    USA

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? Downloadable data in NetCDF format. NetCDF were compressed in zip files (e.g. mcr13_XXXX…, where XXXX is the MMDD) for each day of survey operations.
  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?

Who wrote the metadata?

Dates:
Last modified: 01-Dec-2021
Metadata author:
Andrew W. Stevens
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Oceanographer
2885 Mission Street
Santa Cruz, CA
USA

831-460-7424 (voice)
831-427-4748 (FAX)
astevens@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/mcr13_backscatter_metadata.faq.html>
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