Archive of Digital Chirp Sub-bottom Profile Data Collected During USGS Cruises 08CCT02 and 08CCT03, Mississippi Gulf Islands, July and September 2008

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Frequently anticipated questions:

What does this data set describe?

Title:
Archive of Digital Chirp Sub-bottom Profile Data Collected During USGS Cruises 08CCT02 and 08CCT03, Mississippi Gulf Islands, July and September 2008
Abstract:
In July and September of 2008, the U.S. Geological Survey conducted geophysical surveys to investigate the geologic controls on island framework from Ship Island to Horn Island, MS, as part of a broader USGS study on Coastal Change and Transport (CCT). This report serves as an archive of unprocessed digital Chirp sub-bottom profile data, trackline maps, navigation files, GIS information, FACS logs, observer's logbook, and formal FGDC metadata. Gained digital images of the sub-bottom profiles are also provided.
For more information on the seismic surveys see http://walrus.wr.usgs.gov/infobank/c/c208mi/html/c-2-08-mi.meta.html and http://walrus.wr.usgs.gov/infobank/s/s308mi/html/s-3-08-mi.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:
The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 08CCT02 and 08CCT03 tells us the data were collected in 2008 for research on Coastal Change and Transport (CCT) and the data were collected during the second and third field activity for that study 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 or field activity ID. The naming convention used for each sub-bottom 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 Chirp), '##' is a 2-digit number representing a specific track, and 'a' is a letter representing the section of a line if recording was prematurely terminated or rerun for quality or acquisition problems. The Chirp system uses a signal of continuously varying frequency. The towfish is a sound source and receiver, which is typically towed 1 - 2 m below the sea surface. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by a receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.125 s) and recorded for specific intervals of time (for example, 50 ms). In this way, a two-dimensional vertical image of the shallow geologic structure beneath the ship track is produced. The seismic source employed for Chirp data collection consisted of an EdgeTech SB-424 towfish running EdgeTech's DISCOVER version 3.42 acquisition software and towed about 2 m behind the GPS antenna. The frequency range for both cruises was usually 4 - 16 kHz; however, the frequency range for lines 08c535 - 08c548 and 08c578 - 08c583 of 08CCT02 was 4 - 24 kHz. Sample frequency of the data was 43 kHz, and record length was approximately 75 ms. Shot spacing was about 0.386 m. Standard SEG-Y format allows for the collection of 3 channels of trace data for each recorded shot of Chirp data. Channel 2 is the "real," or in-phase component of the signal, channel 1 is the "imaginary," or quadrature component of the signal, and channel 0 is the "envelope," or product of channels 1 and 2. The acquisition software used for these cruises only saves the envelope data; consequenly, only channel 0 was used to produce the profiles presented here. The archived trace data are in standard SEG-Y, IBM float format (Barry and others, 1975), the first 3,200 bytes of the card image header is in EBCDIC format. The SEG-Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). See the How To Download SEG-Y Data page for download instructions. The SEG-Y formatted trace files have a .sgy extension. Also provided are example SU scripts that allow the user to strip off navigation fixes from the SEG-Y headers, along with a fix for every 1,000 shots, and produce a printable, gained GIF image of each profile. The processed SEG-Y data were exported to Chesapeake Technology, Inc. (CTI) SonarWeb software to produce a geospatially interactive version of the profile that allows the user to obtain a geographic location and depth from the profile for a given cursor position. This information is displayed in the status bar of the browser. NOTE: The only supported Web browsers that properly display all features of the geospatial profiles are Internet Explorer 8 or greater for Windows and Firefox 3.6 or greater for all platforms. For both browsers, the status bar and JavaScript must be enabled. Firefox also requires "Change status bar text" to be checked under Advanced JavaScript Options. If using Internet Explorer 8, you must disable scripts/Active X controls. To do this, right click the information bar (found at the top of the page), left click "Allow Blocked Content...", and then select "Yes". Use of other browsers may result in spurious or no information given in the status window. Firefox may be downloaded at <http://www.mozilla.org/products/firefox>.
  1. How might this data set be cited?
    Forde, Arnell S., Dadisman, Shawn V., Flocks, James G., and Wiese, Dana S., 2011, Archive of Digital Chirp Sub-bottom Profile Data Collected During USGS Cruises 08CCT02 and 08CCT03, Mississippi Gulf Islands, July and September 2008: U.S. Geological Survey Data Series 569, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -89.003140
    East_Bounding_Coordinate: -88.654523
    North_Bounding_Coordinate: 30.267508
    South_Bounding_Coordinate: 30.202395
  3. What does it look like?
    http://pubs.usgs.gov/ds/569/maps/cruisenav/08cct02_03_location.jpg (JPEG)
    Location map of all digital sub-bottom profile data collected during USGS field activities 08CCT02 and 08CCT03. This map was created at a scale of 1:727,850.
    http://pubs.usgs.gov/ds/569/maps/cruisenav/08cct02_area1.jpg (JPEG)
    Trackline map of digital sub-bottom profile data collected offhore of West Ship Island (refer to Area 1 on the location map) during USGS field activity 08CCT02. This map was created at a scale of 1:39,370.
    http://pubs.usgs.gov/ds/569/maps/cruisenav/08cct02_area2.jpg (JPEG)
    Trackline location map of digital sub-bottom profile data collected offshore of East Ship Island (refer to Area 2 on the location map) during USGS field activity 08CCT02. This map was created at a scale of 1:59,500.
    http://pubs.usgs.gov/ds/569/maps/cruisenav/08cct02_area2a.jpg (JPEG)
    Detailed trackline map of digital sub-bottom profile data collected offshore of East Ship Island (refer to Area 2a on the location map) during USGS field activity 08CCT02. This map was created at a scale of 1:31,480.
    http://pubs.usgs.gov/ds/569/maps/cruisenav/08cct02_area2b.jpg (JPEG)
    Detailed trackline map of digital sub-bottom profile data collected offshore of East Ship Island (refer to Area 2b on the location map) during USGS field activity 08CCT02. This map was created at a scale of 1:30,000.
    http://pubs.usgs.gov/ds/569/maps/cruisenav/08cct02_area3.jpg (JPEG)
    Trackline map of digital sub-bottom profile data collected offshore of Horn Island (refer to Area 3 on the location map) during USGS field activity 08CCT02. This map was created at a scale of 1:66,650.
    http://pubs.usgs.gov/ds/569/maps/cruisenav/08cct02_area3a.jpg (JPEG)
    Detailed trackline map of digital sub-bottom profile data collected in Dog Keys Pass and offshore of Horn Island (refer to Area 3a on the Area 3 map) during USGS field activity 08CCT02. This map was created at a scale of 1:22,360.
    http://pubs.usgs.gov/ds/569/maps/cruisenav/08cct03_location.jpg (JPEG)
    Location map of all digital sub-bottom profile data collected during USGS field activity 08CCT03. This map was created at a scale of 1:83,550. Refer to the Lineage section below for the trackline map creation process and other details.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 08-Jul-2008
    Ending_Date: 26-Sep-2008
    Currentness_Reference:
    Data collection interval
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Sub-bottom 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 (latitude and longitude coordinates) for each shot are provided as ASCII text files, along with the day of year and time (UTC) the shot was recorded.
      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 0.000001. 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?
    08cct02.txt, s08cct02.txt, and 08cct02_s.txt; 08cct03.txt, s08cct03.txt, and 08cct03_s.txt
    Shotpoint navigation files (Source: Society of Exploration Geophysicists (SEG)-Y headers (<http://www.seg.org/resources/publications/misc/technical-standards>).)
    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:340738
    Maximum:307302
    UTMY
    UTM-Y coordinate (Zone 16) (Source: Universal Transverse Mercator Geographic Coordinate System)
    Range of values
    Minimum:3342369
    Maximum:3350126
    Line
    Trackline number (Source: U.S. Geological Survey)
    Range of values
    Minimum:08c01
    Maximum:08c729
    Shot
    Shotpoint number (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:20000
    Lon
    Longitude (decimal degrees) (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:-89.274896
    Maximum:-88.856922
    Lat
    Latitude (decimal degrees) (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:29.419127
    Maximum:30.143049
    YEAR
    Year (Source: U.S. Geological Survey)
    Range of values
    Minimum:2008
    Maximum:2008
    DOY:HR:MIN:SEC
    Day of year:hour:minute:second (Source: Coordinated Universal Time) 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 3 to 492 MB.
    Entity_and_Attribute_Overview:
    Graphic image file: Printable profiles are available as GIF images. Interactive profiles are available as HTML pages with accompanying JPEG images. The line navigation maps and trackline maps are JPEG images. The trackline maps contain links to the sub-bottom profiles and line navigation maps.
    Entity_and_Attribute_Overview:
    Navigation file: Navigation files are available as ASCII text files. Provided are raw (unprocessed) shotpoint navigation files, processed shotpoint navigation files, and processed 1,000-shot-interval location files. Fields/Attributes [FID, Shape] marked above with an asterisk (*) were created by ESRI ArcGIS and are used exclusively by the shapefiles created from the aforementioned .txt files; these fields are not included in the original navigation files. All remaing attributes listed in the above section that do not have an accompanying asterisk are found in 08cct02.txt, s08cct02.txt, and 08cct02_s.txt; 08cct03.txt, s08cct03.txt, and 08cct03_s.
    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:
    Barry, K.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended standards for digital tape formats: Geophysics, v. 40, no. 2, p. 344-352. Also available on-line at http://www.seg.org/resources/publications/misc/technical-standards.
    Entity_and_Attribute_Detail_Citation:
    Cohen, J.K., and Stockwell, J.W., Jr., 2010, CWP/SU: Seismic Unix Release 41: A free package for seismic research and processing: Center for Wave Phenomena, Colorado School of Mines. Available on-line at <http://www.cwp.mines.edu/cwpcodes/index.html>.
    Entity_and_Attribute_Detail_Citation:
    Zihlman, F.N., 1992, DUMPSEGY V.1.0: A program to examine the contents of SEG-Y disk-image seismic data: U.S. Geological Survey Open-File Report 92-590, 28 p. Also available on-line at <http://pubs.er.usgs.gov/usgspubs/ofr/ofr92590>.
    Entity_and_Attribute_Detail_Citation:
    Disc Image Credit: Descloitres, J., MODIS Land Rapid Response Team at the NASA Goddard Space Flight Center, 2001, Mississippi.A2001361.1640.250m.jpg. Available on-line at <http://visibleearth.nasa.gov/view_rec.php?id=2364>

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
    • Shawn V. Dadisman
    • James G. Flocks
    • Dana S. Wiese
  2. Who also contributed to the data set?
    Funding for this study was provided by the USGS CMGP. We thank R/V Survey Cat captains Nancy DeWitt and B.J. Reynolds of the USGS - St. Petersburg, FL, for their assistance in data collection. This document was improved by the reviews of Ray Sliter (USGS - Menlo Park, CA) and Ginger Tiling-Range (Jacobs Technology Inc. - St. Petersburg, FL).
  3. To whom should users address questions about the data?
    James Flocks
    USGS
    Geologist
    600 4th Street South
    Saint Petersburg, FL
    USA

    (727) 803-8747 ext. 3012 (voice)
    jflocks@usgs.gov

Why was the data set created?

To archive all digital Chirp sub-bottom profile data and associated files collected during cruises 08CCT02 and 08CCT03.

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: 2008 (process 1 of 8)
    SEG-Y header processing: An issue associated with the acquisition software caused incorrect, initial field record numbers, to be recorded to the trace headers for all lines; consequently, they were renumbered to start at 1 (this was achieved by using the trace sequence numer within line [tracl] header values instead of the recorded shot values) during post-processing. These corrected SEG-Y files are included in this archive.
    Date: 2008 (process 2 of 8)
    Chirp processing: The SEG-Y data were processed with Seismic Unix to produce gained GIF images of the sub-bottom profiles included in this report. A representative Chirp data processing sequence consisted of (1) stripping off navigation data and channel 0 for each shot and converting to SU format, (2) applying automatic gain control, (3) displaying PostScript, and (4) converting of PostScript image to a GIF image. All the processed SEG-Y data were then exported to CTI SonarWeb software to produce a geospatially interactive version of each profile that allows the user to obtain a geographic location and depth for a given cursor position on the profile. Refer to the Supplemental Information section above for details on how to use the interactive profiles. Person who carried out this activity:
    Arnell S. Forde
    U.S. Geological Survey
    Geologist
    600 4th Street South
    St. Petersburg, FL

    (727) 803-8747, ext. 3111 (voice)
    aharrison@usgs.gov
    Date: 2008 (process 3 of 8)
    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 UTM coordinates from latitude and longitude coordinates. Text files for each seismic line were concatenated into two comma-delimited text files (for use with ESRI software), one containing unique shotpoint positions (08cct02.txt and 08cct03.txt) and another containing the 1,000 shot interval locations (s08cct02.txt and s08cct03.txt); both can be viewed within the nav folder, refer to the Browse_Graphic section above for details.
    Date: 2008 (process 4 of 8)
    All concatenated, comma-delimited text files were imported into ArcGIS and saved as either a point or polyline file in the ESRI shapefile format.
    Date: 2008 (process 5 of 8)
    Trackline map creation: The trackline maps and shapefiles provided in this archive were created using the Points to Lines ArcScript (D. Rathert, <http://arcscripts.esri.com/details.asp?dbid=12702>) along with ESRI ArcGIS 9.3 software and then exported to Adobe Illustrator for further editing. The maps were later converted into JPEG format by Adobe GoLive version 8.0.1. The maps are unprojected (geographic coordinates, WGS84). The cities and interstates layers used on the trackline maps were created by ESRI. The USGS is the originator of all other layers used. A map of trackline navigation for each sub-bottom profile was also produced with CTI SonarWeb software.
    Date: 2010 (process 6 of 8)
    Data Series preparation: In addition to the process steps described above, the following steps were taken to produce this Data Series: the handwritten logs were scanned and saved as PDF files, digital FACS logs were created using the handwritten logs and personal accounts of the crew members and saved as PDF files, and an HTML-based format was used to present the various parts of this archive.
    Date: 24-Jan-2017 (process 7 of 8)
    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
    Date: 13-Oct-2020 (process 8 of 8)
    Added keywords section with USGS persistent identifier as theme keyword. 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)
    vatnipp@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 sub-bottom profile 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 sub-bottom profile data were acquired, the position of the vessel was continuously determined by a Coda Octopus F190 receiver, which is accurate to within 20 cm. Positions were recorded and written to the SEG-Y trace headers in latitude and longitude coordinates about every 1 s. The ASCII navigation files and trackline maps have not been corrected to reflect the approximately 2-m offset between the Chirp and GPS antenna. Refer to figure 1 included with this archive (Data Series 569) for a diagram of the acquisition geometries, including the GPS offset measurements. Line navigation maps and interactive profiles generated with CTI SonarWeb software have been corrected for the GPS offsets.
  3. How accurate are the heights or depths?
    These data are not to be used for bathymetry. Depths shown on the Chirp profiles are relative to the depth of the towfish, not to sea level. Furthermore, the raising or lowering of the towfish during a survey (to avoid obstacles or follow relief) produces a relative shift in the multiple reflections seen in the profile, which may be confused as a geologic feature. Any elevation change of the towfish is recorded in the logbooks and is evident on the sub-bottom profiles by steep, abrupt shifts in the seafloor return.
  4. Where are the gaps in the data? What is missing?
    These data are collected along tracklines (2-D) and are therefore inherently incomplete. Geologic details between lines must be inferred. An unknown software malfunction resulted in no SEG-Y data being recorded to the headers for lines 08c565, 08c656 and 08c674.
  5. How consistent are the relationships among the observations, including topology?
    This dataset is from two field activities 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 USGS requests that it 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) 803-8747, ext. 3111 (voice)
    aharrison@usgs.gov
    Contact_Instructions: All of this report except the SEG-Y files is available on-line.
  2. What's the catalog number I need to order this data set? U.S. Geological Survey Data Series 569
  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 standard format (Barry and others, 1975) consists of the following: a 3,600-byte reel identification header, with the first 3,200 bytes consisting of an EBCDIC 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 Size: 18550
      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 PC-compatible ESRI ArcGIS 9.3 software. The shapefiles provided may also be viewed using other versions of ArcView, ArcGIS, or public domain software ArcExplorer (<http://www.esri.com/software/arcexplorer/index.html>) or GeoMapApp (<http://www.geomapapp.org/>) software, which is compatible with all platforms. in format map document, shapefile, metadata Size: 161
      Network links: http://pubs.usgs.gov/ds/569/software/arc/arc.zip
      Data format: The SEG-Y standard format (Barry and others, 1975) consists of the following: a 3,600-byte reel identification header, with the first 3,200 bytes consisting of an EBCDIC 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 Download SEGY data Size: 18550
      Network links: http://cmgds.marine.usgs.gov/data/08cct02/chirp/
      http://cmgds.marine.usgs.gov/data/08cct03/chirp/
    • Cost to order the data: 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: 13-Oct-2020
Metadata author:
Arnell Forde
U.S. Geological Survey
Geologist
600 4th Street South
St. Petersburg, FL
USA

(727) 803-8747, ext. 3111 (voice)
aharrison@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-569metadata.faq.html>
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