Archive of Digital Chirp Subbottom Profile Data Collected During USGS Cruise 13CCT04 Offshore of Petit Bois Island, Mississippi, August 2013

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Frequently anticipated questions:


What does this data set describe?

Title:
Archive of Digital Chirp Subbottom Profile Data Collected During USGS Cruise 13CCT04 Offshore of Petit Bois Island, Mississippi, August 2013
Abstract:
In August of 2013, the U.S. Geological Survey conducted a geophysical survey offshore of Petit Bois Island, Mississippi to investigate the geologic controls on barrier island framework and long-term sediment transport. This report serves as an archive of unprocessed digital chirp subbottom data, trackline maps, navigation files, GIS information, and formal FGDC metadata. Gained digital images of the seismic profiles are provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG Y revision 0 format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG Y files (Zihlman, 1992) are also provided. These data are available for viewing using GeoMapApp (<http://www.geomapapp.org/>) and Virtual Ocean (<http://www.virtualocean.org/>) multi-platform open source software. In addition, the SEG Y files can also be downloaded from the USGS Coastal and Marine Geoscience Data System (<http://cmgds.marine.usgs.gov>).
Supplemental_Information:
The USGS Saint Petersburg Coastal and Marine Science Center (SPCMSC) - St. Petersburg, Fla., assigns a unique identifier to each cruise or field activity. For example, 13CCT04 indicates the data were collected in 2013 for the Coastal Change and Transport (CCT) study, during the fourth field activity for that project in that calendar year. Refer to <http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html> for a detailed description of the method used to assign the cruise ID. The naming convention used for each subbottom line is as follows: yye##a, where 'yy' are the last two digits of the year in which the data were collected, 'e' is a 1-letter abbreviation for the equipment type (for example, c for 424 chirp; i for 512i chirp), '##' is a 2-digit number representing a specific track, and 'a' is a letter representing a section of the line if recording was prematurely terminated or rerun for quality or acquisition problems. All Chirp systems use a signal of continuously varying frequency; the systems used during this survey produce high-resolution, shallow-penetration (typically less than 50-ms) profile images of sub-seafloor stratrigraphy. The towfish contains a transducer that transmits and receives acoustic energy and is typically towed 1–2 meters (m) below the sea surface. As transmitted acoustic energy intersects density boundaries, such as the seafloor or sub-surface sediment layers, some energy is reflected back toward the transducer, received, and recorded by a PC-based seismic acquisition system. This process is repeated at regular intervals (for example, 0.125 seconds (s)) and returned energy is recorded for a specific duration (for example, 50 ms). In this way, a two-dimensional (2-D) vertical image of the shallow geologic structure beneath the towfish is produced. The seismic source utilized during 13CCT04 consisted of an EdgeTech SB-424 and 512i towfish running Discover v. 3.51 acquisition software and towed about 4 m and 28 m, respectively, behind the Global Positioning System (GPS) antenna. The data were acquired using a frequency sweep of 4–20 kilohertz (kHz), a 43 kHz sample frequency, and approximately 65 ms record length. Based on survey speeds of 3.5 knots, the shot spacing was about 0.450 m. The binary portion of the unprocessed seismic data is stored in SEG Y rev. 0 (Barry and others, 1975), IBM float format, which is a standard digital format that can be read and manipulated by most seismic processing software packages; the first 3,200 bytes of the file header are in in American Standard Code for Information Interchange (ASCII) format instead of Extended Binary Coded Decimal Interchange Code (EBCDIC) format. The SEG Y formatted trace files have a .sgy extension. The SEG Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). Also provided are example SU scripts that allow the user to remove navigation fixes from the SEG Y headers, along with a fix for every 1,000 shots, and produce a printable, gained Graphics Interface Format (GIF) image of each profile. The printable profiles provided are GIF images that were gained using SU software. Refer to the Software page of this report for links to example SU processing scripts and USGS software for viewing the SEG Y files (Zihlman, 1992).
  1. How might this data set be cited?
    Forde, Arnell S., Flocks, James G., Kindinger, Jack L., Bernier, Julie C., Kelso, Kyle W., and Wiese, Dana S., 2015, Archive of Digital Chirp Subbottom Profile Data Collected During USGS Cruise 13CCT04 Offshore of Petit Bois Island, Mississippi, August 2013: U.S. Geological Survey Data Series 924, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.541853
    East_Bounding_Coordinate: -88.320964
    North_Bounding_Coordinate: 30.192481
    South_Bounding_Coordinate: 30.077500
  3. What does it look like?
    <http://pubs.usgs.gov/ds/0924/maps/13cct04_location.jpg> (JPEG)
    Figure 2. Location map of all digital chirp subbottom data collected during USGS Field Activity 13CCT04. This map was created at a scale of 1:125,000.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 13-Aug-2013
    Ending_Date: 23-Aug-2013
    Currentness_Reference:
    Data collection interval
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Tabular, vector, and raster digital data
  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 (latitude and longitude and Zone 16 UTM coordinates) for each shot are provided as ASCII text files, along with the date and time time (Universal Coordinated Time (UTC)) the shot was recorded.
    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 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal Degrees. The horizontal datum used is WGS84.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.25722210100002.
  7. How does the data set describe geographic features?
    13cct04.txt, s13cct04.txt, and 13cct04_s.txt
    Shotpoint navigation files (Source: SEG Y headers (<http://www.seg.org/publications/tech-stand>).)
    FID*
    Internal feature number. (Source: ESRI) Sequential unique whole numbers that are automatically generated.
    Shape*
    Feature geometry. (Source: ESRI) Coordinates defining the features.
    UTMX
    UTM-X coordinate (Zone 16) (Source: Universal Transverse Mercator Geographic Coordinate System)
    Range of values
    Minimum:369084
    Maximum:370236
    Units:meters
    UTMY
    UTM-Y coordinate (Zone 16) (Source: Universal Transverse Mercator Geographic Coordinate System)
    Range of values
    Minimum:3335225
    Maximum:3335365
    Units:meters
    Line
    Trackline number (Source: U.S. Geological Survey) The naming convention used for each subbottom line is as follows: yye##a, where 'yy' are the last two digits of the year in which the data were collected, 'e' is a 1-letter abbreviation for the equipment type (for example, c for 424 chirp; i for 512i chirp), '##' is a 2-digit number representing a specific track, and 'a' is a letter representing a section of the line if recording was prematurely terminated or rerun for quality or acquisition problems.
    Shot
    Shotpoint number (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:19000
    Lon
    Longitude (decimal degrees) (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:-88.359261
    Maximum:-88.347286
    Units:decimal degrees
    Lat
    Latitude (decimal degrees) (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:30.141444
    Maximum:30.142586
    Units:decimal degrees
    YEAR
    Year (Source: U.S. Geological Survey)
    Range of values
    Minimum:2013
    Maximum:2013
    DOY:HR:MIN:SEC
    Day of year:hour:minute:second (Source: U.S. Geological Survey) Day of year, hour, minute and second of data acquisition
    Entity_and_Attribute_Overview:
    Binary data file: Trace data are available as binary files in SEG Y format. These files have a .sgy extension and range in size from 4 to 217 MB. These data can be found by going to <http://cmgds.marine.usgs.gov>.
    Entity_and_Attribute_Overview:
    Graphic image file: Printable versions of the subbottom profiles are available as GIF images; links to these images can be found on the Profiles page of this report or by going to <http://pubs.usgs.gov/ds/0924/profiles/printable/>.
    Entity_and_Attribute_Overview:
    Navigation file: Navigation files are available as ASCII text files. Provided are raw (unprocessed) shotpoint navigation files (13c**.txt and 13i**.txt), processed shotpoint navigation (13cct04.txt), processed 1,000-shot-interval location (s13cct04.txt), and a start of line file (13cct04_s.txt). Fields/Attributes [FID, Shape] marked above with an asterisk (*) were created by ESRI ArcGIS and are used exclusively by the shapefiles created from the three aforementioned .txt files; these fields are not included in the original navigation files. All remaining attributes listed above, in the Entity_and_Attribute_Information section, that do not have an accompanying asterisk are found in 13cct04.txt, s13cct04.txt, and 13cct04_s.txt. Raw and processed navigation data files can be found by going to <http://pubs.usgs.gov/ds/0924/nav/>.
    Entity_and_Attribute_Overview:
    GIS file: The GIS project used to create the trackline maps is provided as a .zip file composed of ESRI map documents, shapefiles, and metadata.
    Entity_and_Attribute_Detail_Citation: Information is derived from SEG Y headers.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Arnell S. Forde
    • James G. Flocks
    • Jack L. Kindinger
    • Julie C. Bernier
    • Kyle W. Kelso
    • Dana S. Wiese
  2. Who also contributed to the data set?
    Funding and (or) support for this study was provided by the USGS Coastal and Marine Geology Program, Mississippi Coastal Improvements Program (MsCIP), and the Northern Gulf of Mexico Ecosystem Change and Hazard Susceptibility Project. We thank Research Vessel (R/V) Tommy Munro captain Paul Beaugez and crew (University of Southern Mississippi/Gulf coast Research Laboratory - Biloxi, MS) for their assistance in data collection and Will Pfeiffer and Nancy DeWitt for their assistance with bathymetry data processing. This document was improved by the reviews of Marci Marot and Samantha Kuzma of the USGS - St. Petersburg, Fla. and Cherokee Nation Technology Solutions, respectively. Disc Image Credit: Descloitres, J., MODIS Land Rapid Response Team at the National Aeronautics and Space Administration Goddard Space Flight Center, 2001, Mississippi.A2001361.1640.250m.jpg. Available on-line at http://visibleearth.nasa.gov/view_rec.php?id=2364.
  3. To whom should users address questions about the data?
    Arnell S. Forde
    U.S. Geological Survey
    Geologist
    600 4th Street South
    Saint Petersburg, FL
    USA

    (727) 502-8000 (voice)
    aforde@usgs.gov

Why was the data set created?

To archive all digital chirp subbottom profile data and associated files collected during cruise 13CCT04.

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: 2013 (process 1 of 5)
    Chirp processing: The SEG Y data were processed with Seismic Unix to produce gained GIF images of the subbottom profiles included in this report. A representative chirp data processing sequence consisted of (1) stripping off navigation data for each shot and converting to SU format, (2) applying automatic gain control, (3) generating a PostScript image of the traces, and (4) converting the PostScript image to a GIF image. For additional SU processing and script details, please refer to <http://pubs.usgs.gov/ds/0924/software/su/readme.txt>. Person who carried out this activity:
    Arnell S. Forde
    U.S. Geological Survey
    Geologist
    600 4th Street South
    St. Petersburg, FL

    (727) 502-8000 (voice)
    aforde@usgs.gov
    Data sources used in this process:
    • SEG Y
    Data sources produced in this process:
    • printable/SEG Y.gif
    Date: 2013 (process 2 of 5)
    Navigation processing: Shotpoint navigation, start of line, and 1,000-shot-interval location files were extracted using Seismic Unix software and output as ASCII text files; they were then processed with PROJ.4.7.0 (<http://trac.osgeo.org/proj/>) to generate Universal Transverse Mercator (UTM) coordinates (WGS84, Zone 16, meters) from latitude and longitude coordinates. Text files for each seismic line were concatenated into comma-delimited text files (for use with ESRI (Environmental Systems Research Institute) software); one containing unique shotpoint positions (13cct04.txt), another containing the 1,000-shot-interval locations (s13cct04.txt), and the last containing start of line locations (13cct04_s); which can be viewed within the nav folder. Person who carried out this activity:
    Arnell S. Forde
    U.S. Geological Survey
    Geologist
    600 4th Street South
    St. Petersburg, FL

    (727) 502-8000 (voice)
    aforde@usgs.gov
    Data sources used in this process:
    • 13c**.txt, 13i**.txt
    Data sources produced in this process:
    • 13cct04.txt
    • s13cct04.txt
    • 13cct04_s.txt
    Date: 2013 (process 3 of 5)
    All concatenated, comma-delimited text files were imported into ArcGIS and saved as either a point or polyline file in the ESRI shapefile format. Trackline map creation: The trackline maps were created using ESRI ArcGIS 10.1 software. The processed navigation file, 13cct04.txt, was imported into ArcMap 10.1 and processed using the ArcScript, Points to Lines, to create a line shapefile of the cruise tracklines (13cct04_trkln). The 1,000-shot-interval file, s13cct04.txt, and the start of line file, 13cct04_s.txt, were imported into ArcMap as point shapefiles 13cct04_shots and 13cct04_sol. Please refer to the shapefile metadata included in the ArcGIS map document in the Software section of this archive for additional details. All maps were exported to Adobe Illustrator v. 14 for further editing converted into JPEG format by Adobe Dreamweaver v. 10 Build 4117. The maps are unprojected (geographic coordinates, WGS84). The USGS is the originators of all layers used. Please see the ArcGIS readme file for detailed information about the GIS files used in this report. Person who carried out this activity:
    Arnell S. Forde
    U.S. Geological Survey
    Geologist
    600 4th Street South
    St. Petersburg, FL

    (727) 502-8000 (voice)
    aforde@usgs.gov
    Data sources used in this process:
    • 13cct04.txt
    • s13cct04.txt
    • 13cct04_s.txt
    Data sources produced in this process:
    • 13cct04_trkln.shp
    • 13cct04_shots.shp
    • 13cct04_sol.shp
    Date: 2013 (process 4 of 5)
    Data Series preparation: In addition to the process steps described above, the following steps were taken to produce this Data Series report: the handwritten cruise logs were scanned and saved as a PDF file, digital logs were created by J. Bernier using the cruise logs and the personal accounts of crew members and saved as PDF files, and an HTML-based format was used to present the various parts of this archive. Person who carried out this activity:
    Arnell S. Forde
    U.S. Geological Survey
    Geologist
    600 4th Street South
    St. Petersburg, FL

    (727) 502-8000 (voice)
    aforde@usgs.gov
    Date: 24-Jan-2017 (process 5 of 5)
    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?
    Cohen, J.K., and Stockwell, J.W., Jr., CWP/SU, 2010, Seismic Unix Release 41: A free package for seismic research and processing, Center for Wave Phenomena, Colorado School of Mines.

    Online Links:

    Zihlman, F.N., USGS, 1992, DUMPSEGY V1.0: A program to examine the contents of SEG Y disk-image seismic data: U.S. Geological Survey Open-File Report 92–590.

    Online Links:

    Other_Citation_Details: 28 pages
    Barry, K.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended standards for digital tape formats: Geophysics v. 40, no. 2.

    Online Links:

    Other_Citation_Details: pages 344–352

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 subbottom 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?
    As the subbottom data were acquired, the position of the vessel was continuously determined by a CodaOctopus F190 DGPS [Digital Global Positioning System] and subsequently sent to Hypack 2010 navigation software to ensure a consistent grid spacing during data collection. Positions were recorded and written to trace headers in latitude and longitude coordinates about every 1 s using navigation from the CodaOctopus F190 receiver with OmniSTAR High Performance (HP) correction (accurate to within 20 cm). The approximately 4-m (424 chirp) and 28-m (512i chirp) offset between the chirp shot and ship's GPS was not accounted for during acquisition nor have the ASCII navigation files and trackline maps been corrected to reflect the offset.
  3. How accurate are the heights or depths?
    These data are not to be used for bathymetry. Two-way travel (TWT) times shown on the printable profile images are relative to the chirp towfish position, not to the sea surface.
  4. Where are the gaps in the data? What is missing?
    These data are collected along tracklines (2-D) and are therefore inherently incomplete. Due to system malfunctions, subbottom data using both the 512i and 424 systems.
  5. How consistent are the relationships among the observations, including topology?
    This dataset is from one field activity 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 originator of the data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    Arnell Forde
    U.S. Geological Survey
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    aforde@usgs.gov
    Contact_Instructions:
    All of this report is available online. The SEG Y files are downloadable from the Coastal and Marine Geoscience Data System (<http://cmgds.marine.usgs.gov>).
  2. What's the catalog number I need to order this data set? U.S. Geological Survey Data Series 924
  3. What legal disclaimers am I supposed to read?
    This DVD publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: The SEG Y rev. 0 format (Barry and others, 1975) presented here consists of the following: a 3,600-byte reel identification header, with the first 3,200 bytes consisting of an ASCII header block followed by a 400-byte binary header block, both of which include information specific to line and reel number; a trace data block that follows the reel identification header, with the first 240 bytes of each trace block consisting of the binary trace identification header; and seismic data samples that follow the trace identification header. in format SEG Y rev. 0 Size: 8960
      Network links: https://cmgds.marine.usgs.gov/data/13CCT04/agcsegy/
      Media you can order: DVD (format ISO 9660)
      Note: Unix, Linux, DOS, Macintosh
      Data format: The GIS project used to create the trackline maps is composed of map documents, shapefiles, and metadata. Map documents were created with ESRI ArcGIS 10.1 software. The shapefiles provided may also be viewed using other versions of ESRI desktop software including their free software or ArcGIS Explorer (<http://www.esri.com/software/arcgis/explorer/index.html>). in format map document, shapefile, metadata Size: 138
      Network links: https://pubs.usgs.gov/ds/0924/software/arc/arc.zip
    • Cost to order the data: None, if obtained online; otherwise, prices vary.

    • Special instructions:
      Publications are available from USGS Information Services, Box 25286, Federal Center, Denver, CO 80225-0046 (telephone: 1-888-ASK-USGS, e-mail: infoservices@usgs.gov).
  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 public domain software Seismic Unix (<http://www.cwp.mines.edu/cwpcodes/index.html>).

Who wrote the metadata?

Dates:
Last modified: 19-Mar-2019
Metadata author:
Arnell Forde
U.S. Geological Survey
Geologist
600 4th Street South
St. Petersburg, FL
USA

(727) 502-8000 (voice)
aforde@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/ds-924.faq.html>
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