Backscatter A [CSUMB]--Offshore of Ventura, California

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What does this data set describe?

Title: Backscatter A [CSUMB]--Offshore of Ventura, California
This part of SIM 3254 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3254) of the Offshore of Ventura map area, California. The raster data file is included in "," which is accessible from <>. The acoustic-backscatter map of the Offshore of Ventura map area, California, was generated from backscatter data collected by California State University, Monterey Bay, Seafloor Mapping Lab (CSUMB) and by the U.S. Geological Survey (USGS). These metadata describe the acoustic-backscatter data collected by CSUMB and reprocessed by the USGS (see "BackscatterB_USGS_OffshoreVentura_metadata.txt" metadata for a description of the acoustic-backscatter data collected by the USGS). The majority of the acoustic-backscatter data within the Offshore of Ventura map area, California, was collected by CSUMB in the summers of 2006 and 2007, using a 244-kHz Reson 8101 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 sediment type. 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).
  1. How should this data set be cited?

    Dartnell, Peter, Kvitek, Rikk G. , Phillips, Eleyne L. , and Cochrane, Guy R. , 2013, Backscatter A [CSUMB]--Offshore of Ventura, California:.

    This is part of the following larger work.

    Johnson, Samuel Y. , Dartnell, Peter, Cochrane, Guy R. , Golden, Nadine E. , Phillips, Eleyne L. , Ritchie, Andrew C. , Kvitek, Rikk G. , Greene, H. Gary , Krigsman, Lisa M. , Endris, Charles A. , Seitz, Gordon G. , Gutierrez, Carlos I. , Sliter, Ray W. , Erdey, Mercedes D. , Wong, Florence L. , Yoklavich, Mary M. , Draut, Amy E. , Hart, Patrick E. , and Cochran, Susan A. , 2013, California State Waters Map Series--Offshore of Ventura, California: Scientific Investigations Map SIM 3254, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -119.44
    East_Bounding_Coordinate: -119.25
    North_Bounding_Coordinate: 34.38
    South_Bounding_Coordinate: 34.22

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 2006
    Ending_Date: 2007
    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, type Grid Cell

    2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 11
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -117.00000
      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 2.0
      Ordinates (y-coordinates) are specified to the nearest 2.0
      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 meters.
      The flattening of the ellipsoid used is 1/298.257223563.

  7. How does the data set describe geographic features?

    The complete 2006 - 2007 backscatter data were originally archived as an ESRI grid with the following attributes:
    Cell size = 2.0
    Number of rows = 8955
    Number of columns = 8955
    Data type = floating point
    Xmin = 274890.00
    Xmax = 292800.00
    Ymin = 3788680.00
    Ymax = 3806590.00
    Minimum value = 0
    Maximum value = 253
    Mean = 130.68
    Standard deviation = 17.89
    Coordinate system description
    Projection  UTM
    Zone  11
    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)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    Peter Dartnell
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Physical Scientist
    400 Natural Bridges Dr.
    Santa Cruz, CA 95060-5792

    (831) 460-7415 (voice)
    (831) 427-4709 (FAX)

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.

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: 2007 (process 1 of 2)
    CSUMB acoustic-backscatter data were collected in the summers of 2006 and 2007, using a 244-kHz Reson 8101 multibeam echosounder. During the CSUMB mapping missions, an Applanix position and motion compensation system (POS/MV) was used to accurately position the vessel during data collection, and it also accounted for vessel motion such as heave, pitch, and roll (position accuracy, +/-2 m; pitch, roll, and heading accuracy, +/-0.02 degrees; heave accuracy, +/-5 percent, or 5 cm). NavCom 2050 GPS receiver (CNAV) data were used to account for tidal-cycle fluctuations, and 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) using vertical-position data from the CNAV receiver.

    Person who carried out this activity:

    Carrie Bretz
    Seafloor Mapping Lab, California State University Monterey Bay
    Projects Manager, GIS; Metadata Supervisor
    100 Campus Center, Bldg 13
    Seaside, CA 93955

    (831) 582-4197 (voice)

    Date: 2009 (process 2 of 2)
    USGS received original Caris HIPS/SIPS projects from CSUMB for CSUMB survey blocks A-H. Backscatter data were postprocessed by the USGS using CARIS7.0/Geocoder software. Geobars were created for each survey line using the beam-averaging engine. 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. The contrast and brightness of some geobars were adjusted to better match the surrounding geobars. Individual geobars were mosaicked together at 2-m resolution using the auto-seam method. The mosaics were then exported from CARIS as georeferenced TIFF images, imported into a GIS, converted to GRIDs, and clipped to the Offshore of Ventura map boundary.

    Person who carried out this activity:

    Pete Dartnell
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Physical Scientist
    400 Natural Bridges Dr.
    Santa Cruz, CA 95060-5792

    (831) 460-7415 (voice)

  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?

    Not applicable for raster data.

  2. How accurate are the geographic locations?

    Estimated to be no less than 2 m, owing to 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

  4. Where are the gaps in the data? What is missing?


  5. How consistent are the relationships among the observations, including topology?


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Please recognize the U.S. Geological Survey (USGS) and California State University, Monterey Bay, Seafloor Mapping Lab (CSUMB). USGS-authored or produced data and information are in the public domain. This information is not intended for navigational purposes. Read and fully comprehend the metadata prior to data use. Uses of these data should not violate the spatial resolution of the data. Where these data are used in combination with other data of different resolution, the resolution of the combined output will be limited by the lowest resolution of all the data. Acknowledge the USGS and CSUMB in products derived from these data. Share data products developed using these data with the U.S. Geological Survey. This database has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use. Although this Federal Geographic Data Committee-compliant metadata file is intended to document these data in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.

Who wrote the metadata?

Last modified: 15-Mar-2013
Last Reviewed: 15-Mar-2013
Metadata author:
Peter Dartnell
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Physical Scientist
400 Natural Bridges Dr.
Santa Cruz, CA 95060-5792

(831) 460-7415 (voice)
(831) 427-4709 (FAX)

Metadata standard:
Content Standard for Digital Geospatial Metadata ("CSDGM version 2") (FGDC-STD-001-1998)

Generated by mp version 2.9.6 on Mon Jul 08 15:33:19 2013