PNG formatted images of EdgeTech SB-424 seismic-reflection profiles collected by the U.S. Geological Survey -Woods Hole Coastal and Marine Science Center offshore of the Elizabeth Islands, MA, 2010.

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Frequently-anticipated questions:

What does this data set describe?

Title:
PNG formatted images of EdgeTech SB-424 seismic-reflection profiles collected by the U.S. Geological Survey -Woods Hole Coastal and Marine Science Center offshore of the Elizabeth Islands, MA, 2010.
Abstract:
These data were collected under a cooperative agreement between the Massachusetts Office of Coastal Zone Management (CZM) and the U.S. Geological Survey (USGS), Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center (WHCMSC). Initiated in 2003, the primary objective of this program is to develop regional geologic framework information for the management of coastal and marine resources. Accurate data and maps of seafloor geology are important first steps toward protecting fish habitat, delineating marine resources, and assessing environmental changes due to natural or human impacts. The project is focused on the inshore waters of coastal Massachusetts, primarily in water depths of 2-30 meters. Data collected for the mapping cooperative have been released in a series of USGS Open-File Reports (<http://woodshole.er.usgs.gov/project-pages/coastal_mass/html/current_map.html>). The data collected in this study area located around the western extent of the Elizabeth Islands includes high resolution bathymetry, acoustic-backscatter intensity, seismic-reflection, and navigation data. These data were collected during a nearshore cruise in September 2010 onboard the R/V Rafael using the following equipment: an SEA Ltd SwathPlus interferometric sonar (234 kHz), Klein 3000 dual frequency sidescan sonar, an Edgetech 424 chirp subbottom profiling system, and 4 GPS antennae. More information about the cruise conducted as part of the project: Geologic Mapping of the Seafloor Offshore of Massachusetts can be found on the Woods Hole Coastal and Marine Science Center Field Activity webpage: <http://quashnet.er.usgs.gov/data/2010/10003/>
  1. How should this data set be cited?

    U.S. Geological Survey, 2012, PNG formatted images of EdgeTech SB-424 seismic-reflection profiles collected by the U.S. Geological Survey -Woods Hole Coastal and Marine Science Center offshore of the Elizabeth Islands, MA, 2010.: Open-File Report 2011-1184, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Pendleton, Elizabeth A. , Twichell, David C. , Foster, David S. , Worley, Charles R. , Irwin, Barry J. , and Danforth, William W. , 2012, High-Resolution Geophysical Data From the Sea Floor Surrounding the Western Elizabeth Islands, Massachusetts: Open-File Report 2011-1184, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -70.992374
    East_Bounding_Coordinate: -70.849060
    North_Bounding_Coordinate: 41.460852
    South_Bounding_Coordinate: 41.388525

  3. What does it look like?

    <https://pubs.usgs.gov/of/2011/1184/GIS_catalog/seisimage/seisimage.png> (PNG)
    PNG image of SB-424 chirp seismic reflection profile

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

    Beginning_Date: 10-Sep-2010
    Ending_Date: 16-Sep-2010
    Currentness_Reference: Data were not collected on 20100915 due to weather conditions.

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

    Geospatial_Data_Presentation_Form: remote-sensing image

  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 pixel

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

  7. How does the data set describe geographic features?

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?

    David C. Twichell
    U.S. Geological Survey
    Oceanographer
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2266 (voice)
    508-457-2310 (FAX)
    dtwichell@usgs.gov

Why was the data set created?

PNG images of each seismic profile were generated in order to incorporate images of the seismic data into Geographic Information System (GIS) projects and data archives utilizing HTML. These PNG images represent approximately 253 km of chirp seismic data collected with the EdgeTech 424 in Sept. 2010. This format is universal and yields an easily browseable pictorial view of the seismic profiles. Each profile image is hotlinked to its corresponding trackline navigation contained within a polyline shapefile ('2010-003-FA_Chirp424_tracklines.shp'), and even 500 shot-point locations are available in a point shapefile ('2010-003-FA_Chirp424_500sht.shp). All of these data are available in an ESRI ArcMap project, as well as separate .zip archives on this digital data DVD archive (<https://pubs.usgs.gov/of/2011/1184/GIS_catalog/>).

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    U.S. Geological Survey.

    Type_of_Source_Media: disc
    Source_Contribution:
    Approximately 253 km of high-resolution chirp seismic-reflection profiles were collected using an EdgeTech 3100 portable sub-bottom system and SB-424 towfish (4-24 kHz) on the R/V Rafael of Woods Hole, MA. SonarWiz.MAP +SBP (version 4) acquisition software was used to control the Geo-Star topside unit and digitally log trace data in the Society of Exploration Geophysicists Y (SEG-Y), revision 1, standard format (Norris and Faichney, 2002). The SB-424 towfish was towed astern of the starboard side of the vessel. Navigation coordinates were obtained from a DGPS antenna mounted 3-m above the waterline on the interferometric sonar pole and logged to the SEG-Y trace headers. Data were acquired using a 4.0 to 24.0 kHz frequency sweep, a 10 millisecond pulse length, a 0.1667 second shot rate, a 23 microsecond sample interval, and a 130 millisecond record length. A total of 253 km of seismic data were collected.

  2. How were the data generated, processed, and modified?

    Date: 30-Oct-2010 (process 1 of 2)
    An executable C-shell script called on SIOSEIS (version 10.2.25) to: 1) read the raw SEG-Y data so that shot number begins at one and increments by one for each SEG-Y file; 2) apply a time varying gain: a(i) = a(i) * (t*1000.)**alpha where a(i) is the trace and t is the time of the trace sample in seconds (alpha was 1.5).; 3) apply Automatic Gain Control (AGC) to every trace. AGC is a type of amplitude normalization (modification) that results in the amplitudes being more uniform, especially when the window length decreases. AGC starts by finding the first non-zero sample and then calculates the average absolute value of the window. Successive windows are calculated by shifting the window down one sample. Each average absolute value is then turned into a multiplier by dividing the average by an output level. A window length of 10 ms was used and 65 percent of the computed multiplier was applied.; and, 4) write the gained traces to new SEG-Y files.

    Person who carried out this activity:

    David S. Foster
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2271 (voice)
    508-457-2310 (FAX)
    dfoster@usgs.gov

    Date: Oct-2010 (process 2 of 2)
    A Seismic Unix (version 4.1) script was used to read the gained SEG-Y files and plot the data as 8-bit gray scale Postscript files using the Seismic Unix 'psimage' algorithm. All images were created with a horizontal scale of 100 traces per inch. Images were plotted within a constant 14-inch vertical window of 60 milliseconds (Two-Way Travel Time) duration, yielding a vertical resolution of about 5 milliseconds per inch. The Postscript images were then converted with ImageMagick to PNG format for visualization in an image viewer.

    Person who carried out this activity:

    David S. Foster
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700x2271 (voice)
    (508) 457-2310 (FAX)
    dfoster@usgs.gov

  3. What similar or related data should the user be aware of?

    Stockwell, John, 2008, CWP/SU: Seismic Uni*x: Center for Wave Phenomena - Colorado School of Mines, Golden, CO.

    Online Links:

    Henkart, Paul, 2007, SIOSEIS: Scripps Institution of Oceanography, University of California - San Diego, LaJolla, CA.

    Online Links:

    Norris, Michael W. , and Faichney, Alan K. , 2002, SEGY Rev.1 Data Exchange Format1: Society of Exploration Geophysicists, Tulsa, OK.

    Online Links:

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?

    The SB-424 was towed from a starboard-side davit with 2-m of cable out on the R/V Rafael. The navigation for these data were acquired with an Communications Systems International (CSI), Inc. LGBX Pro Differential Global Positioning System (DGPS) receiver and an antenna mounted on the cabin of the R/V Rafael. All DGPS data are referenced to WGS84. The SonarWiz.MAP +SBP acquisition software logged the navigation coordinates (in arcseconds) to individual trace headers, but towfish layback and horizontal distance between the CSI antenna and the towfish was not accounted for. Based on horizontal offsets between the towfish and GPS receiver, and towfish motion behind the vessel, the resulting horizontal accuracy is assumed to be +/- 25 m.

  3. How accurate are the heights or depths?

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

    l8f3 and l26f1.001 had fewer than 50 shot points, so these lines were not included.

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

    Processed seismic data were converted to portable network graphic (PNG) format for ease of seismic trace display. Quality control was conducted during processing. File naming is generally lxfy.png. Where x is the survey line number and y is the file number along a given survey line. There are a few exceptions that resulted from autofile changing in SonarWiz.MAP +SBP. A few lines are named lxfy_.png, and a few others are lxfy_00z.png; where x and y are the same as above and z is the autofile change number.

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 are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.

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

    Elizabeth Pendleton
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700x2259 (voice)
    (508) 457-2310 (FAX)
    ependleton@usgs.gov

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

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. 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 materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

  4. How can I download or order the data?

  5. Is there some other way to get the data?

    Digital copies of these chirp seismic data may also be obtained in the SEG-Y Rev. 1 standard format upon request. The data would be packaged on DVD, and contain the chirp-processed, envelope traces.

  6. What hardware or software do I need in order to use the data set?

    These data can be viewed with any PNG image viewing software.

Who wrote the metadata?

Dates:
Last modified: Oct-2010
Metadata author:
Elizabeth Pendleton
U.S. Geological Survey
Geologist
384 Woods Hole Rd.
Woods Hole, MA 02543-1598

(508) 548-8700x2259 (voice)
(508) 457-2310 (FAX)
ependleton@usgs.gov

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

Generated by mp version 2.8.25 on Fri Nov 18 14:46:50 2011