BackscatterB [EM300]--Offshore Aptos, California

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Frequently anticipated questions:

What does this data set describe?

Title: BackscatterB [EM300]--Offshore Aptos, California
Abstract:
This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Aptos map area, California. Backscatter data are provided as two separate grids depending on mapping system and processing method. This metadata file refers to the data included in "BackscatterB_EM300_OffshoreAptos.zip," which is accessible from https://doi.org/10.5066/F7K35RQB. These data accompany the pamphlet and map sheets of Cochrane, G.R., Johnson, S.Y., Dartnell, P., Greene, H.G., Erdey, M.D, Dieter, B.E., Golden, N.E., Hartwell, S.R., Ritchie, A.C., Kvitek, r.G., Maier, K.L., Endris, C.A., Davenport, C.W., Watt, J.T., Sliter, R.W., Finlayson, D.P., and Krigsman, L.M., (G.R. Cochrane and S.A. Cochran, eds.), 2016, California State Waters Map Series—Offshore of Aptos, California: U.S. Geological Survey Open-File Report 2016–1025, 43 p., 10 sheets, scale 1:24,000, https://doi.org/10.3133/ofr20161025.
The acoustic-backscatter map of Offshore of Aptos, California was generated from backscatter data collected by the U.S. Geological Survey (USGS) and by Monterey Bay Aquarium Research Institute (MBARI). Mapping was completed between 1998 and 2009, using a combination of a 234-kHz SWATHplus bathymetric sidescan-sonar system and a 30-kHz Simrad EM-300 multibeam echosounder. 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?
    Dartnell, Peter, Ritchie, Andrew C., and Finlayson, David P., 2015, BackscatterB [EM300]--Offshore Aptos, California: Data Series DS 781, U.S. Geological Survey, Reston, VA.

    Online Links:

    This is part of the following larger work.

    Golden, Nadine E., 2015, California State Waters Map Series Data Catalog: Data Series DS 781, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.00
    East_Bounding_Coordinate: -121.80
    North_Bounding_Coordinate: 37.00
    South_Bounding_Coordinate: 36.84
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5576269de4b032353caef2b1?f=__disk__b8%2Fb7%2F78%2Fb8b778256890d471466bd6bebdef342ebb30be7b&allowOpen=true (JPEG)
    Acoustic backscatter imagery offshore of Aptos, California
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1998
    Ending_Date: 2009
    Currentness_Reference:
    ground condition
  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 3522 x 3566 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 5.0
      Ordinates (y-coordinates) are specified to the nearest 5.0
      Planar coordinates are specified in Meters
      The horizontal datum used is WGS84.
      The ellipsoid used is WGS84.
      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
    BackscatterB [EM300] intensity value (Source: ESRI)
    VALUE
    Backscatter intensity values (Source: ESRI)
    Range of values
    Minimum:-55
    Maximum:-8
    Units:Floating point values representing intensity
    Entity_and_Attribute_Overview:
    The EM-300 acoustic-backscatter grid was originally archived as an ESRI grid with the following attributes: 
    Cell size = 5.0
Number of rows = 3522
Number of columns = 3566

Data type = floating point

Boundary
Xmin = 588830
Xmax = 606660
Ymin = 4077950
Ymax = 4095560

Statistics
Minimum value = -55
Maximum value = -8
Mean = -35.91
Standard deviation = 2.39

Coordinate system description
Projection  UTM
Zone  10
Datum  WGS84
Units  meter
    Entity_and_Attribute_Detail_Citation: none

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Peter Dartnell
    • Andrew C. Ritchie
    • David P. Finlayson
  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
    US

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

Why was the data set created?

These data are intended for science researchers, students, policy makers, and the general public. These data can be used with geographic information systems or other software to identify seafloor features.

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: 2014 (process 1 of 5)
    During the MBARI mapping mission an Applied Analytic POS MV (Position and Orientation System for Marine Vessels) was used to accurately position the vessel and account for vessel motion with navigational input from a kinematic GPS system. Soundings were corrected for variations in water-column sound velocity using data from a SeaBird CTD and Sippican T5 expendable bathythermographs. The MBARI EM-300 backscatter data covering the head of Soquel Submarine Canyon were used in the Offshore of Aptos map. The USGS downloaded the original MBARI survey line files from the National Geophysical Data Center (NGDC) on-line bathymetry server (http://www.ngdc.noaa.gov/mgg/bathymetry/relief.html). Using MB-Systems, amplitude values were extracted from the survey line files and exported as one overall XYZ file. The XYZ file was gridded at 5-m spatial resolution in Fledermaus software (QPS), converted to an ASCIIRaster file, and imported into a geographic information system (GIS). The grid was clipped to the offshore of Aptos map boundary. Person who carried out this activity:
    Pete Dartnell
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Physical Scientist
    2885 Mission Street
    Santa Cruz, CA
    USA

    (831) 460-7415 (voice)
    pdartnell@usgs.gov
    Date: 05-Oct-2017 (process 2 of 5)
    Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Alan O. Allwardt
    Contractor -- Information Specialist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7551 (voice)
    831-427-4748 (FAX)
    aallwardt@usgs.gov
    Date: 26-Apr-2018 (process 3 of 5)
    Added keywords from Coastal and Marine Ecological Classification Standard (CMECS) to metadata. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Alan O. Allwardt
    Contractor -- Information Specialist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7551 (voice)
    831-427-4748 (FAX)
    aallwardt@usgs.gov
    Date: 08-Sep-2020 (process 4 of 5)
    Edits were made to bring the metadata up to current PCMSC standards including standardizing authors' names, adding a doi# link, correcting typos, refining keywords, and using current access and distribution liability statements. Point of Contact and Metadata Contact information sections were changed to static PCMSC contact information. No data were changed. Users are advised to compare the metadata date of this file to any similar file to ensure they are using the most recent version. Person who carried out this activity:
    Susan A Cochran
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission St.
    Santa Cruz, CA
    United States

    831-460-7545 (voice)
    scochran@usgs.gov
    Date: 19-Oct-2020 (process 5 of 5)
    Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?
    Cochrane, Guy R., Johnson, Samuel Y., Dartnell, Peter, Greene, H. Gary, Erdey, Mercedes D., Dieter, Bryan E., Golden, Nadine E., Hartwell, Stephen R., Ritchie, Andrew C., Kvitek, Rikk G., Maier, Katherine L., Endris, Charles A., Davenport, Clifton W., Watt, Janet T., Sliter, Ray W., Finlayson, David P., and Krigsman, Lisa M., 2016, California State Waters Map Series--Offshore of Aptos, California: Open-File Report 2016-1025, U.S. Geological Survey, Reston, VA.

    Online Links:

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?
    Estimated to be no less than 2 m, owing 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?
    Not applicable to acoustic-backscatter imagery.
  4. Where are the gaps in the data? What is missing?
    Complete
  5. How consistent are the relationships among the observations, including topology?
    Unspecified

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. This information is not intended for navigation purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey
    345 Middlefield Rd
    Menlo Park, CA
    USA

    (650) 329-4309 (voice)
  2. What's the catalog number I need to order this data set? The download includes the image (.tif), the world registration file (.tfw), tif.ovr, and a color ramp file. The text (.txt), XML (.tif.xml), HTML, and FAQ versions of the metadata for the BackscatterB [EM300] data layer of Offshore Aptos, California are also included in the download.
  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 "zip" command and can be unzipped with Winzip (or other tool) on Windows systems. To utilize these data, the user must have software capable of uncompressing the WinZip file and importing and viewing an Esri ArcMap TIFF. Users should download the ArcGIS Project File, OffshoreAptosGIS.mxd.zip, a compressed (with the "zip" command) version of the ArcMap document (.mxd) that has all the data layers loaded in the table of contents for "Offshore Aptos" and has all the data symbolized as on the data release map sheets. Download and save this ArcGIS project file, including all data layers, to the directory the user has created for this GIS.

Who wrote the metadata?

Dates:
Last modified: 19-Oct-2020
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
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)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/SeriesReports/DS_DDS/DS_781/XMLs_on_ScienceBase/F7K35RQB_OffshoreAptos/BackscatterB_EM300_OffshoreAptos_metadata.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:17:51 2021