Archive of Boomer Seismic Reflection Data, collected on USGS Cruise 99ASR01, Lake Okeechobee, Florida, 29 June - 30 June, 1999.

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Frequently anticipated questions:


What does this data set describe?

Title:
Archive of Boomer Seismic Reflection Data, collected on USGS Cruise 99ASR01, Lake Okeechobee, Florida, 29 June - 30 June, 1999.
Abstract:
This report consists of two-dimensional marine seismic reflection profile data from Lake Okeechobee, Fla., that were acquired in June of 1999 aboard the R/V G. K. Gilbert. These data are available in a variety of formats, including binary, ASCII and GIF images. Binary data are in Society of Exploration Geophysicists (SEG) SEG-Y format and may be downloaded for further processing or display.
For more information on the seismic surveys see http://walrus.wr.usgs.gov/infobank/g/g399fl/html/g-3-99-fl.meta.html
These data are also available via GeoMapApp (http://www.geomapapp.org/) and Virtual Ocean (http://www.virtualocean.org/) earth science exploration and visualization applications.
Supplemental_Information:
Seismic reflection profiles are acquired by means of an acoustic source (usually generated electronically), and a hydrophone or hydrophone array. Both elements are typically towed in the water behind a survey vessel. The sound source emits a short acoustic pulse, which propagates through the water and sediment columns. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), and detected at the hydrophone. This process is repeated at intervals ranging between 100 ms and 1 s depending on the source type. In this way a two-dimensional image of the geologic structure beneath the ship track is constructed. Seismic data are stored in SEG-Y format, which is a standard digital format that can be read and manipulated by most seismic-processing software packages. The SEG-Y file format includes a 3200-byte descriptive header that contains detailed information regarding the data acquisition and processing parameters. All data presented here are stored in SEG-Y, Integer, Motorola format. The SEG-Y formatted trace data files have a .tra extension. Additional recording parameters for each seismic data file can also be found in the .par file associated with each .tra file. However, the .par files and the cent_rmc.pln file are only needed to replay the data with Triton Elics Delph Seismic software. The seismic energy source employed here was a boomer transducer towed on a sled at the lake surface providing 200 joules per shot. The reflected energy was received by an Innovative Transducer Inc. (ITI) solid core streamer and recorded by PC-based Triton Elics Delph Seismic acquisition software. The ITI streamer contains 10 hydrophones evenly spaced over 6 meters, however only data received by elements 5-8 where summed, resulting in a higher signal to noise ratio for the data. The streamer was positioned parallel to the boomer sled and laterally separated from it by 7 m. The sled was towed 20 m behind the Global Positioning System (GPS) antennae. The sample frequency of the data was 16000 Hz and the total record length was 200 ms for tracklines oke699_1 to oke699_7 and 300 ms for tracklines oke699_8 to oke69911. The fire rate was every 0.5 s, which resulted in a shot spacing of about 1 m based on survey speeds of 3.5-4 knots. GPS navigation was provided by a Trimble Centurian P-Code receiver directly fed to the acquisition system. The shotpoint navigation provided in this report has not been corrected to reflect the 20 m offset of the source to the GPS antenna. The horizontal accuracy of the navigation data was within 31m. The navigation data are stored as flat ASCII files. The raw navigation files were generated by the Delph Seismic Software for each trackline and provide the following information for each unique position fix, all separated by commas: shotpoint number, longitude, latitude, heading, speed, date, and Greenwich Mean Time(GMT). The edited navigation file contains all the unique fixes for each trackline with spurious points removed. A separate file containing edited navigation for every 500th shotpoint interval is also provided. Both the edited navigation and the 500th shotpoint navigation files contain six fields separated by commas: shotpoint number, date, GMT, longitude, latitude, and the trackline number. This navigation data can be used to plot trackline maps of the seismic profiles at any scale or map projection desired. The trackline map provided on this disc is a Mercator projection and was created with ESRI's GIS software ArcView 3.2. The map was then exported to Adobe Illustrator and saved as a GIF image. This GIF image is viewable with your WWW browser.
  1. How might this data set be cited?
    Brewer, Gina M., Dadisman, Shawn V., Kindinger, Jack L., Weise, Dana S., and Flocks, James G., 2001, Archive of Boomer Seismic Reflection Data, collected on USGS Cruise 99ASR01, Lake Okeechobee, Florida, 29 June - 30 June, 1999.: U.S. Geological Survey Open-File Report OFR-01-165, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -80.834383 W
    East_Bounding_Coordinate: -80.72581 W
    North_Bounding_Coordinate: +27.19386 N
    South_Bounding_Coordinate: +27.11907 N
  3. What does it look like?
    http://pubs.usgs.gov/of/2001/of01-165/MAPS/okeemap.GIF (GIF)
    Map of trackline data collected on USGS Cruise 99ASR01, in June of 1999, in Lake Okeechobee, Fla. This map is a mercator projection prepared in ESRI's ArcView 3.2, exported to Adobe Illustrator for further editing and then saved as a GIF image.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 29-Jun-1999
    Ending_Date: 30-Jun-1999
    Currentness_Reference:
    Data assumed to be constant over time but may change due to geologic processes.
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Seismic Reflection Profile Section
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference:
      Horizontal X and Y locations for each shot location are provided in ASCII position files, along with the time the shot was recorded in Greenwich Mean Time (GMT).
      This is a Point data set.
    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 0.000278. Longitudes are given to the nearest 0.000278. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is WGS 84.
      The ellipsoid used is WGS 1984.
      The semi-major axis of the ellipsoid used is 6378137 m.
      The flattening of the ellipsoid used is 1/298.257.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    Binary data file: Each profile is available as a binary file in Society of Exploration Geophysicists SEG-Y format. A SEG-Y file consists of 1) a 3200-byte file identification record of ASCII formatted general information; 2) a 400-byte binary record with information such as sample rate and record length specific to the data set; and 3) multiple records, one seismic reflection trace per record. Each trace record is preceded by a 240-byte "trace header" containing information such as trace number and acquisition day and time specific to each trace. The trace data are represented as a time series of unitless 16-bit integer or 32-bit real numbers proportional to the reflection coefficient. The SEG-Y file is useful only if you have access to specialized software designed to process and display seismic reflection data. These SEG-Y files have a .tra extension. These .tra files range in size from 21 MB to 80 MB.
    Entity_and_Attribute_Overview:
    Graphic image file: Each profile is available as a GIF image. The trackline maps provided are GIF images that contain hot-links to the seismic profile GIF images. The profiles range in size from 508KB to 1.9MB.
    Entity_and_Attribute_Detail_Citation:
    Barry, K.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended standards for digital tape formats: Geophysics, v. 40, n. 2, p. 344 - 352. Also available online at: <http://www.seg.org/publications/tech-stand/index_body.html>

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Gina M. Brewer
    • Shawn V. Dadisman
    • Jack L. Kindinger
    • Dana S. Weise
    • James G. Flocks
  2. Who also contributed to the data set?
    We thank Keith Ludwig, captain of the R/V G. K. Gilbert for his help in the data collection; Dave Foster and Jenna Hill, of the USGS Seafloor Mapping Group in Woods Hole, Mass., for providing examples of their archives; Jon Childs with the USGS in Menlo Park, Calif., who provided examples of his formal metadata; and Trent Faust and Rob Wertz with the USGS here in St.Petersburg, Fla., for their help in the web design and technical layout of the CD-ROM.
  3. To whom should users address questions about the data?
    Jack Kindinger
    U.S. Geological Survey
    Oceanographer
    600 Fourth Street South
    St. Petersburg, FL
    USA

    (727)803-8747 X3018 (voice)
    jkindinger@usgs.gov

Why was the data set created?

Marine seismic reflection data are used to image and map sedimentary and structural features of the seafloor and subsurface. The main objective of this cruise was to ascertain if data useful to the Everglades Aquifer Storage and Recovery Project could be acquired using seismic techniques. These data proved to be useful in mapping the extent and thickness of shallow sedimentary units beneath Lake Okeechobee, Fla., and in assessing other submarine geologic characteristics and 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: 2001 (process 1 of 4)
    Boomer processing: Raw SEG-Y data was processed with SU to produce the GIF formatted seismic profiles included in this report. A representative data processing sequence consisted of: 1)Bandpass filter: 300-500-2500-3000 Hz; 2)Automatic gain control; 3)Postscript display at 50 ms/in and 300 shots/in for tracklines oke699_1 to oke699_7 and at 75 ms/in and 300 shots/in for tracklines oke699_8 to oke699_11; 4)Convert Postscript files to GIF format
    Date: 2001 (process 2 of 4)
    Positional (navigation) data: As the seismic reflection data were acquired, the position of the vessel was determined continuously with the Global Positioning System (GPS). GPS positions were recorded approximately every second, and written to the SEG-Y header. The ASCII navigation files were extracted from the SEG-Y headers using SU scripts and edited for obvious spurious data values.
    Date: 2001 (process 3 of 4)
    Open File preparation: No processing has been done to the SEG-Y data files provided on this CD-ROM. The data were displayed as 8-bit gray scale Postscript files using the Seismic Unix 'psimage' algorithm. The Postscript images were then converted to GIF images with Aladdin Ghostscript. Only the GIF images are presented here.
    Date: 24-Jan-2017 (process 4 of 4)
    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
  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?
    The validity or accuracy of marine seismic reflection profiles is highly qualitative, and depends on equipment and operating condition variables. Visual inspection of the images rendered from the data did not show any major anomalies.
  2. How accurate are the geographic locations?
    The position accuracy was determined with a Trimble Centurian P-Code Receiver. Absolute position accuracy was within 31 m.
  3. How accurate are the heights or depths?
    The vertical position was lake level and there has been no corrections to a datum or for tidal variations.
  4. Where are the gaps in the data? What is missing?
    These data are collected along tracklines (2D). Therefore, data are inherently incomplete. Geologic details between lines must be inferred. Tracklines oke699_1 to oke699_7 were recorded to 200 ms. Tracklines oke699_8 to oke69911 were recorded to 300 ms.
  5. How consistent are the relationships among the observations, including topology?
    This data set is from a single cruise with consistent instrument calibrations.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None. These data are held in the public domain.
Use_Constraints:
The U.S. Geological Survey requests to be acknowledged as the originator of the data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    Rob Wertz
    U.S. Geological Survey
    Manager, Data Management Group
    600 Fourth Street South
    St. Petersburg, FL
    USA

    (727)803-8747 X3045 (voice)
    rwertz@usgs.gov
    Contact_Instructions:
    Data may be available online only by special arrangement with the distributor above.
  2. What's the catalog number I need to order this data set? U.S. Geological Survey Open-File Report 01-XXX CD-ROM
  3. What legal disclaimers am I supposed to read?
    This Compact Disc-Read Only Memory (CD-ROM) publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Although all data published on this CD-ROM have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: The SEG-Y standard format (Barry and others, 1975) consists of the following: A 3600-byte reel identification header with the first 3200 bytes consisting of an EBCDIC header block and a 400-byte binary header block. Both headers include information specific to line and reel number. The trace data block follows the reel identification header. The first 240 bytes of each trace block is the binary trace identification header. The seismic data samples follow the trace identification header. Our data uses an ASCII header block instead of the standard EBCDIC. in format SEG-Y Size: 650
      Media you can order: CD-ROM (format ISO 9660)
      Note: Unix, Linux, DOS, MAC
      Data format: The SEG-Y standard format (Barry and others, 1975) consists of the following: A 3600-byte reel identification header with the first 3200 bytes consisting of an EBCDIC header block and a 400-byte binary header block. Both headers include information specific to line and reel number. The trace data block follows the reel identification header. The first 240 bytes of each trace block is the binary trace identification header. in format SEGY data download Size: 650
      Network links: http://cmgds.marine.usgs.gov/data/99asr01/
    • Cost to order the data:

      available from the Denver Open-File Sales Department, for $50.00.

    • Special instructions:
      This archive is stored on an ISO 9660 CD-ROM.
  5. What hardware or software do I need in order to use the data set?
    Use of SEG-Y data requires specialized seismic processing software, such as Unix or Linux based public-domain software Seismic Unix developed by the Colorado School of Mines Center for Wave Phenomena, which can be downloaded from <http://www.cwp.mines.edu/cwpcodes> free of charge.

Who wrote the metadata?

Dates:
Last modified: 17-Apr-2018
Metadata author:
Gina M. Brewer
U.S. Geological Survey
Geologist, Data Management Group
600 Fourth Street South
St. Petersburg, FL
USA

(727)803-8747 X3120 (voice)
gmbrewer@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/of2001-165metadata.faq.html>
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