Seafloor character from sidescan sonar data-Santa Barbara Channel

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Frequently anticipated questions:

What does this data set describe?

Seafloor character from sidescan sonar data-Santa Barbara Channel
Substrate was classified using the method of (Cochrane and Lafferty, 2002) for this study. Sea floor character derived from towed sidescan sonar data is available for the mainland coast within the study area from USGS online publications (Cochrane and others, 2003; Cochrane and others, 2005). The number of substrate classes was reduced because rugosity could not be derived for all areas due to the lack of bathymetry data for other data sets used in the study.
References Cited:
Cochrane, G.R., Nasby, N.M., Reid, J.A., Waltenberger, B., Lee, K.M., 2003, Nearshore Benthic Habitat GIS for the Channel Islands National Marine Sanctuary and Southern California State Fisheries Reserves Volume 1: U.S. Geological Survey Open-File Report 03-85,
Cochrane, G.R., and Lafferty, K.D., 2002, Use of acoustic classification of sidescan sonar data for mapping benthic habitat in the Northern Channel Islands, California: Continental Shelf Research, v. 22, p. 683-690.
Cochrane, G.R., Conrad, J.E., Reid, J.A., Fangman, S., Golden, N.E., 2005, The Nearshore Benthic Habitat GIS for the Channel Islands National Marine Sanctuary and Southern California State Fisheries Reserves, Volume II; Version 1.0: U.S. Geological Survey Open-File Report 2005-1170,
  1. How might this data set be cited?
    Cochrane, Guy R., 2015, Seafloor character from sidescan sonar data-Santa Barbara Channel: data release DOI:10.5066/F7QF8QXF, U.S. Geological Survey, Coastal and Marine Geology Program, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Cochrane, Guy R., 2015, Data Release for Santa Barbara Channel Regional Importance of Manmade Structures as Rockfish Nurseries Study: Data Release doi:10.5066/F7QF8QXF, U.S. Geological Survey, Coastal and Marine Geology Program, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -119.674
    East_Bounding_Coordinate: -119.331
    North_Bounding_Coordinate: 34.084
    South_Bounding_Coordinate: 33.960
  3. What does it look like? (map service)
    Seafloor character types Santa Barbara Channel and Northern Channel Islands.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2002
    Ending_Date: 2004
    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 7465 x 16191 x 1, type Pixel
    2. What coordinate system is used to represent geographic features?
      The map projection used is WGS 1984 UTM 11N.
      Projection parameters:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -117
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000
      False_Northing: 0.0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.0001
      Ordinates (y-coordinates) are specified to the nearest 0.0001
      Planar coordinates are specified in Meter
      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?
    The attributes include VALUE - code for the seafloor character classes, COUNT - number of pixels. The raster can be added to any ESRI ArcMap project. (Source: ESRI)
    Internal feature number. (Source: ESRI) Sequential unique whole numbers that are automatically generated.
    This seafloor-character class was produced using video-supervised maximum-likelihood classification of sidescan sonar backscatter (intensity of return). Derivative homogeneity, entropy, and backscatter intensity were used as variants in the classification. In order to combine the results with results for areas that had no rugosity information this data set was reduce to a simple hard versus sogt bottom classification. A value of 1 indicates deposits of mud and sand thick enough to support infauna. A value of 2 indicates hard bottom including gravel, cobble, boulder, and bedrock. (Source: ESRI)
    Range of values
    Units:Integers representing seafloor character classes
    The number of pixels (2m x 2m size grid cell) represented in each seafloor class (see Attribute: VALUE). (Source: ESRI)
    Range of values
    Units:Integer representing pixel count

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Guy R. Cochrane
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Guy R. Cochrane
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA

    (831)460-7554 (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 to identify local seafloor character.

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: 2011 (process 1 of 3)
    The seafloor-character map was produced using video-supervised maximum likelihood classification of and intensity of return from sidescan sonar and textural indices derived from the backscatter data. The classification was supervised using signatures defined by hand-drawn polygons located through sediment samples and video-observation ground truthing applying methodology described in Cochrane (2002). The two variants used in this classification were homogeneity and . Both mimic terrain ruggedness using the variation in intensity of grid cells within a neighborhood. This method effectively captures variability into a single measure.
    Classes I, II and III values were delineated using maximum likelihood analysis. The resulting map (gridded at 2 m) was cleaned by hand to remove data-collection artifacts (for example trackline nadir). Editing was performed in Photoshop, with which individual pixels were selected and values adjusted to remove noise. Selection occurred without antialiasing, and the resulting grid was identical but for the edited pixels.
    Date: 2011 (process 2 of 3)
    The sea floor character rasters were reclassed combining classes II and III. The blocked rasters were mosaicked into a single raster.
    Date: 19-Oct-2020 (process 3 of 3)
    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)
  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?
    Pixel resolution 2 m.
  2. How accurate are the geographic locations?
    Positional information reflects the position of the ship and was collected using a WAAS-enabled GSP unit, recording at between 1 to 2 nm. DGPS (WAAS) accuracy for position is less than 3 meters. (From Garmin GPSMAP 76C/76CS Specifications, M01-10108-00, Rev0304, <https://>). Towed sidescan distance from ship is variable depending on water depth and layback distance between the gps unit and the stern. Accuracy is on the order of 100 meters.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Survey area is defined by coverage of sidescan backscatter datasets.
  5. How consistent are the relationships among the observations, including topology?
    Classification was done on the basis of training samples delineated by interpreter. The classification was performed using mathematical algorithms then hand-edited by the interpreter to remove noise.

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 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 - 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?
  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,, 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 ‚ÄúSantaBarbaraChannelGeohab‚ÄĚ 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?

Last modified: 19-Oct-2020
Metadata author:
Guy R. Cochrane
U.S. Geological Survey, Pacific Coastal and Marine Science Center
2885 Mission Street
Santa Cruz, California

(831)460-7554 (voice)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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