Tracklines of Sidescan-Sonar Survey conducted within Gulf of Farallones, 1989, by the U.S. Geological Survey

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Frequently-anticipated questions:

What does this data set describe?

Title:
Tracklines of Sidescan-Sonar Survey conducted within Gulf of Farallones, 1989, by the U.S. Geological Survey
Abstract:
In 1989, the U.S. Geological Survey (USGS) began a major geologic and oceanographic investigation of the Gulf of the Farallones continental shelf system, designed to evaluate and monitor human impacts on the marine environment (Karl and others, 2002). The study region is located off the central California coast, adjacent to San Francisco Bay and encompasses the Gulf of the Farallones National Marine Sanctuary. Geologic mapping of this area included the use of various remote sensing and sampling techniques such as sub-bottom profiling, sidescan-sonar and bathymetric mapping, gravity core and grab sampling, and photography. These data were used to define the surficial sediment distribution, underlying structure and sea floor morphology of the study area. The primary focus of this report is to present a georeferenced, digital sidescan-sonar mosaic of the study region. The sidescan-sonar data were acquired with the AMS-120 (120kHz) sidescan-sonar system during USGS cruise F9-89-NC. The dataset covers approximately 1000 km² of the continental shelf between Point Reyes, California and Half Moon Bay, California, extending west to the continental shelf break near the Farallon Islands. The sidescan-sonar mosaic displays a heterogenous sea-floor environment, containing outcropping rock, ripples, dunes, lineations and depressions, as well as flat, featureless sea floor (Karl and others, 2002). These data, along with sub-bottom interpretation and ground truth data define the geologic framework of the region. The sidescan-sonar mosaic can be used with supplemental remote sensing and sampling data as a base for future research, helping to define the local current regime and predominant sediment transport directions and forcing conditions within the Gulf of Farallones.
  1. How should this data set be cited?

    Sweeney, Edward M. , 2004, Tracklines of Sidescan-Sonar Survey conducted within Gulf of Farallones, 1989, by the U.S. Geological Survey: U.S. Geological Survey, U.S. Geological Survey, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Sweeney, Edward M. , Danforth, William W. , Karl, Herman A. , O'Brien, Thomas F. , and Schwab, William C. , 2004, The Gulf of Farallones: Sidescan-Sonar Imagery: USGS Open-File Report 2004-1082, USGS, USGS, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -123.383570
    East_Bounding_Coordinate: -122.688740
    North_Bounding_Coordinate: 37.977070
    South_Bounding_Coordinate: 37.587810

  3. What does it look like?

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

    Beginning_Date: 02-Aug-1989
    Ending_Date: 15-Aug-1989
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: Vector

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • String (358)

    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 0.000089992. Longitudes are given to the nearest 0.000089992. 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 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.

  7. How does the data set describe geographic features?

    Tracklines
    ESRI ArcGIS 8.3 vector shapefile (Source: ESRI)

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    LineNumber
    Internal Definition (Source: ESRI)

    Internal identification value

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?

    Edward M. Sweeney
    U.S. Geological Survey
    Research Assistant
    384 Woods Hole Rd.
    Woods Hole, MA 02543

    (508) 548-8700 x2307 (voice)
    (508) 457-2310 (FAX)
    esweeney@usgs.gov

Why was the data set created?

These data represent the sidescan-sonar trackline navigation data during the geophysical survey in the Gulf of the Farallones off the coast of central California.

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: 2004 (process 1 of 1)
    Navigation data was acquired using three systems: (1) Global Positioning System (GPS); (2) LORAN-C; and (3) shore-based, line-of-sight transponder net (Del Norte system). For real time positioning, the primary system was chosen either manually by the navigator or selected automatically by computer.

    The navigation is reformatted into a comma-delimited ArcView Ungenerate text format. The file is then imported into ArcView, and a vector line shapefile is generated. The line numbers for each trackline are stored in an ASCII file listing unique track ID and line number. This file is imported into ArcView and ArcMap as a table. The file is then joined to the line shapefile by the unique track ID. The table for the trackline file is then edited, a new field created and the line number information is written to this new field. After writing the line number information to the trackline shapefile, the table join is removed, and the file is saved. This permanently saves the line number with the corresponding trackline.

    Person who carried out this activity:

    Edward M. Sweeney
    U.S. Geological Survey
    Research Assistant
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-548-8700 x2307 (voice)
    508-457-2310 (FAX)
    esweeney@usgs.gov

  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?

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

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

    These data represent the sidescan-sonar tracklines conducted during a geophysical cruise within the Gulf of Farallones in 1989 by the U.S. Geological Survey.

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

    These data represent the sidescan-sonar tracklines conducted during a geophysical cruise within the Gulf of Farallones in 1989 by the U.S. Geological Survey. These data were navigated by GPS and LORAN-C. For real time positioning, the primary system was chosen either manually by the navigator or selected automatically by computer. Tracklines were within 100m of preplotted tracks when using GPD and LORAN-C and within a few meters when navigating under the Del Norte system.

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:
Public domain data from the U.S. government is freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of this dataset.

  1. Who distributes the data set? (Distributor 1 of 1)

    Nancy Soderberg
    U.S. Geological Survey
    Data Librarian
    384 Woods Hole Rd.
    Woods Hole, MA 02543
    USA

    (508) 548-8700 x2275 (voice)
    (580)457-2313 (FAX)
    nsoderberg@usgs.gov

  2. What's the catalog number I need to order this data set?

    Sidescan-sonar Tracklines (ESRI Shapefile)

  3. What legal disclaimers am I supposed to read?

    Although this data set and its lineage have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data or its related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related items. Users must assume responsibility for the proper use of these data. The data should not be used at resolutions for which they are not intended. The data have not been reviewed for conformity with U.S. Geological Survey editorial standards, or the North American Strigraphic code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the US Government.

  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 07-Apr-2004
Metadata author:
Edward M. Sweeney
U.S. Geological Survey
Research Assistant
384 Woods Hole Rd.
Woods Hole, MA 02543

(508) 548-8700 x2307 (voice)
(508) 457-2310 (FAX)
esweeney@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.8.7 on Mon Jul 19 12:01:31 2004