Acoustic backscatter intensity from multibeam echosounder data collected offshore of Cape Mendocino, California

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Frequently anticipated questions:


What does this data set describe?

Title:
Acoustic backscatter intensity from multibeam echosounder data collected offshore of Cape Mendocino, California
Abstract:
This 2-m-resolution acoustic backscatter data for the Offshore of Cape Mendocino, California, map area is part of USGS Data Series 781 (Golden, 2019). Backscatter data were collected by Fugro Pelagos in 2008 using a combination of 400-kHz Reson 7125, 240-kHz Reson 8101, and 100-kHz Reson 8111 multibeam echosounder systems. The data were post-processed by the California State University Monterey Bay Seafloor Mapping Lab. The acoustic backscatter data are available as a georeferenced TIFF image. Within the final imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and composition. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).
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. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology.
  1. How might this data set be cited?
    Kvitek, Rikk, and Cochrane, Guy R., 20231130, Acoustic backscatter intensity from multibeam echosounder data collected offshore of Cape Mendocino, California: data release DOI:10.5066/P9U0SUGL, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Cochrane, Guy R., 2023, Bathymetry, backscatter intensity, and benthic habitat offshore of Cape Mendocino, California: data release DOI:10.5066/P9U0SUGL, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Cochrane, G.R., 2023, Bathymetry, backscatter intensity, and benthic habitat offshore of Cape Mendocino, California: U.S. Geological Survey data release, https://doi.org/10.5066/P9U0SUGL.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -124.541854
    East_Bounding_Coordinate: -124.375972
    North_Bounding_Coordinate: 40.539173
    South_Bounding_Coordinate: 40.37736
  3. What does it look like?
    Backscatter_OffshoreCapeMendocino.jpg (JPEG)
    Preview image of the acoustic-backscatter data offshore of Cape Mendocino
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2008
    Currentness_Reference:
    ground condition at time data were collected.
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: GeoTIFF
  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. It contains the following raster data types:
      • Dimensions 9131 x 7027 x 1, type Grid Cell
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 10
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123.00000
      Latitude_of_Projection_Origin: 0.00000
      False_Easting: 500000.0
      False_Northing: 0.00
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 10.0
      Ordinates (y-coordinates) are specified to the nearest 10.0
      Planar coordinates are specified in Meters
      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_844.
      The semi-major axis of the ellipsoid used is 6378137.00.
      The flattening of the ellipsoid used is 1/298.257223563.
  7. How does the data set describe geographic features?
    value
    backscatter intensity as a digital value (Source: Producer defined)
    Entity_and_Attribute_Overview:
    The complete 2-m resolution Offshore of Cape Mendocino backscatter raster is an 8-bit integer raster. It has a minimum (least reflective) value of 0 and a maximum (most reflective) value of 254.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Rikk Kvitek
    • Guy R. Cochrane
  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)
    pcmsc_data@usgs.gov

Why was the data set created?

The surveys were conducted to map surficial geology and benthic habitat as part of the USGS California Seafloor Mapping Program, a collaboration with California State University Monterey Bay (CSUMB) and the National Oceanic and Atmospheric Administration (NOAA) funded by the California Ocean Protection Council. These data are intended to provide regional bathymetric information in California State waters for offshore resource and ecosystem management. These data are also intended for science researchers, students, policy makers, and the general public. These data can be used with geographic information systems or other software to help identify geomorphologic features and surficial lithology. These data are not intended to be used for navigation.

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: 2016 (process 1 of 2)
    Multibeam echosounder (MBES) data were collected by Fugro Pelagos in 2008, using a combination of 400-kHz Reson 7125, 240-kHz Reson 8101, and 100-kHz Reson 8111 multibeam echosounders. An Applanix POS-MV (Position and Orientation System for Marine Vessels) was used to accurately position the vessels during data collection, and it also accounted for vessel motion such as heave, pitch, and roll, with navigational input from GPS receivers. Smoothed Best Estimated Trajectory (SBET) files were postprocessed from logged POS-MV files. Sound-velocity profiles were collected with an Applied Microsystems (AM) SVPlus sound velocimeter. Soundings were corrected for vessel motion using the Applanix POS-MV data, for variations in water-column sound velocity using the AM SVPlus data, and for variations in water height (tides) and heave using the postprocessed SBET data (California State University, Monterey Bay, Seafloor Mapping Lab, 2016). The Reson backscatter data were postprocessed using Geocoder software. The backscatter intensities were radiometrically corrected (including despeckling and angle-varying gain adjustments), and the position of each acoustic sample was geometrically corrected for slant range on a line-by-line basis. After the lines were corrected, they were mosaicked into 0.5-m resolution images (California State University, Monterey Bay, Seafloor Mapping Lab, 2016).
    Date: 2023 (process 2 of 2)
    The 0.5-m-resolution images were mosaiced and clipped to the study area boundary by the USGS. The mosaics were then exported as 2-m resolution georeferenced TIFF images.
  3. What similar or related data should the user be aware of?
    Golden, Nadine E., 2019, California State Waters Map Series Data Catalog: Data Series DS 781, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Golden, N.E., compiler, 2019, California State Waters Map Series Data Catalog, https://doi.org/10.3133/ds781.
    California State University, Monterey Bay, Seafloor Mapping Lab, 2016, Southern California 2008 CSMP surveys: California State University, Monterey Bay, Seafloor Mapping Lab Data Library.

    Online Links:

    Other_Citation_Details:
    California State University, Monterey Bay, Seafloor Mapping Lab, 2016, Southern California 2008 CSMP surveys: California State University, Monterey Bay, Seafloor Mapping Lab Data Library.

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

  1. How well have the observations been checked?
    Not applicable for raster data.
  2. How accurate are the geographic locations?
    The POS MV position and motion compensation system has a horizontal positional accuracy of about 0.5 m with DGPS corrections and roll and pitch accuracies of about 0.02 degrees (http://www.measutronics.com/wp-content/uploads/2011/01/posmv320_specifications.pdf). Accuracies of final products may be lower due to water depth and total propagated uncertainties of the mapping systems, which include sonar system, position and motion compensation system, and navigation, as well as data processing that includes sounding cleaning, gridding, and datum transformations.
  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?
    No formal logical accuracy tests were conducted.

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 and the California State University Monterey Bay Seafloor Mapping Lab as the originators of the dataset and in products derived from these data. This information is not intended for navigation purposes.
  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 GeoTIFF format (Backscatter_OffshoreCapeMendocino.tif), along with a tif world file (.tfw) and 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?
  5. What hardware or software do I need in order to use the data set?
    The downloadable data file has been compressed with the Windows 10 "zip" command and can be unzipped using Windows File Explorer or with Winzip (or other tools). To utilize these data, the user must have software capable importing and viewing a GeoTIFF file.

Who wrote the metadata?

Dates:
Last modified: 30-Nov-2023
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)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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Generated by mp version 2.9.51 on Fri Dec 15 14:16:32 2023