Archive of Digital Chirp Subbottom Profile Data Collected During USGS Cruises 09CCT03 and 09CCT04, Mississippi and Alabama Gulf Islands, June and July 2009
In June and July of 2009, the U.S. Geological Survey conducted geophysical surveys to investigate the geologic controls on island framework from Cat Island, Mississippi, to Dauphin Island, Alabama, as part of a broader USGS study of Coastal Change and Transport (CCT). This report serves as an archive of unprocessed digital Chirp seismic reflection data, trackline maps, navigation files, Geographic Information System (GIS) files, Field Activity Collection System (FACS) logs, observer's logbook, and formal Federal Geographic Data Committee (FGDC) metadata. Gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided.
Purpose:
To archive all digital Chirp subbottom profile data and associated files collected during cruises 09CCT03 and 09CCT04. NOTE: Cruise 09CCT03A survey data were collected as a subset during cruise 09CCT03; this dataset is restricted to Cat Island. Although listed as a separate cruise (in this archive and on the FACS forms), it was not officially assigned a unique ID by the St. Petersburg Coastal and Marine Science Center (SPCMSC); this naming convention was adopted in the field to help distinguish this smaller cruise from the larger one during the data acquisition and archival processes.
Supplemental_Information:
The USGS SPCMS assigns a unique identifier to each cruise or field activity. For example, 09CCT03 and 09CCT04 tell us the data were collected in 2009 for research on Coastal Change and Transport (CCT) and the data were collected during the third and fourth field activities 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 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 and i for 512i 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. All Chirp systems use a signal of continuously varying frequency; the EdgeTech SB-512i and SB-424 Chirp systems used during these surveys produce high resolution, shallow penetration (less than 50-ms) profile images beneath the seafloor. 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 during 09CCT03 consisted of an EdgeTech SB-424 towfish running EdgeTech's DISCOVER v. 3.50 acquisition software and towed about 2 m behind the GPS antenna. The frequency range for the entire cruise was 4 - 20 kHz. Sample frequency of the data was 43 kHz, and record length was 100 ms.
The source utilized during 09CCT04 consisted of an EdgeTech SB-512i towfish also running DISCOVER v. 3.50 acquisition software; however, it was towed about 9 m behind the GPS antenna. The frequency range varied between 1 - 10 kHz and 0.7 - 12 kHz. Sample frequency of the data was 43 kHz, and record length was 75 ms. Based on survey speeds of 3.5 knots, the shot spacing for both cruises 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 are in ASCII, instead of EBCDIC format. Some data were collected in the EdgeTech's proprietary JSF format and later converted to SEG-Y; all remaining lines were collected in both formats. The SEG-Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). 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 version 3.16.0096 PRO 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 cursor position; this information is displayed in the status bar of the browser. Please note that clicking on the profile image switches it to "Expanded View" (a compressed image of the entire line), and cursor tracking is not available in this mode. 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.com/en-US/firefox/>. Macintosh Instructions (Firefox Only): From the Menu Bar go to Firefox > Preferences > Content (tab) > Checkmark "Enable JavaScript"> Click Advanced... > Checkmark "Change Status Bar Text". Verify that the status bar is enabled by selecting View from the Menu Bar and looking for a checkmark next to "Status Bar"; if the check is missing, highlight and select the text to activate the bar.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20090609
Ending_Date: 20090701
Currentness_Reference: Data collection interval
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -89.167925
East_Bounding_Coordinate: -88.316583
North_Bounding_Coordinate: 30.269472
South_Bounding_Coordinate: 30.186064
Keywords:
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: geoscientificinformation
Theme_Keyword: oceans
Theme:
Theme_Keyword_Thesaurus: General
Theme_Keyword: Geology
Theme_Keyword: Coastal Information
Theme_Keyword: Marine
Theme_Keyword: Subbottom profile
Theme_Keyword: Seismic Reflection
Theme_Keyword: Chirp
Theme_Keyword: Society of Exploration Geophysicists
Theme_Keyword: SEG-Y
Theme_Keyword: Coastal Change and Transport
Theme_Keyword: CCT
Theme_Keyword: 09CCT03
Theme_Keyword: 09CCT04
Place:
Place_Keyword_Thesaurus: Names Information System (GNIS) Content Charcterization
Place_Keyword: Mississippi
Place_Keyword: Alabama
Place_Keyword: Cat Island
Place_Keyword: West Ship Island
Place_Keyword: East Ship Island
Place_Keyword: Horn Island
Place_Keyword: Petit Bois Island
Place_Keyword: Dauphin Island
Place_Keyword: Biloxi Bay
Place_Keyword: Dog Keys Pass
Place_Keyword: Mississippi Sound
Place_Keyword: Gulf of Mexico
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.
Location map of all digital subbottom profile data collected during USGS field activities 09CCT03, 09CCT03A, and 09CCT04. This map was created at a scale of 1:726,775.
Area 1 trackline map of digital subbottom profile data collected from Horn Island to Dauphin Island (refer to figure 2 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:229,950.
Area 1a detailed trackline map of digital subbottom profile data collected offshore of Horn Island (refer to figure 3 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:50,000.
Area 1b detailed trackline map of digital subbottom profile data collected offshore of Horn and Petit Bois Islands (refer to figure 3 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:32,000.
Area 1c detailed trackline map of digital subbottom profile data collected offshore of Petit Bois Island (refer to figure 3 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:49,250.
Area 1d detailed trackline map of digital subbottom profile data collected offshore of Dauphin Island (refer to figure 3 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:44,470.
Area 2 trackline map of digital subbottom profile data collected offshore of Cat Island (refer to figure 2 for location) during USGS field activity 09CCT03A. This map was created at a scale of 1:71,000.
Directory containing printable images of all subbottom profiles. The record lengths for cruises 09CCT03 and 09CCT04 are 100 ms and 75 ms, respectively. Since no geologically significant structures could be seen in the 09CCT03 profiles below 50 ms, the printable profiles do not display data beyond this point.
Processed 1,000 shotpoint navigation file for all tracklines collected during field activity 09CCT04.
Browse_Graphic_File_Type: ASCII Text File
Data_Set_Credit:
Funding for this study was provided by the USGS CMGP. We thank R/V Survey Cat captains Nancy DeWitt and B.J. Reynolds and R/V G.K. Gilbert captain Rich Young of the USGS - St. Petersburg, FL for their assistance in data collection. We would also like to thank Elizabeth Pendleton of the USGS Coastal and Marine Science Center - Woods Hole, MA, for her help in data processing. This document was improved by the reviews of Mark Hansen (USGS - SPCMSC) and Jamie Bonisteel-Cormier (Jacobs Technology Inc. - St. Petersburg, FL).
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
The validity or accuracy of marine subbottom 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.
Logical_Consistency_Report:
These data are from three different cruises. Differences may occur in navigation, acquisition equipment, and acquisition geometry between vessels and field activities. Horizontal accuracy varies with navigation equipment used, and signal-to-noise ratio of the data changes with towfish used. However, for most purposes, the profile data are comparable for all systems used.
Completeness_Report:
These data are collected along tracklines (2-D) and are therefore inherently incomplete. Geologic details between lines must be inferred. As a result of either generator failure or an unknown software malfunction, no SEG-Y data were recorded for lines 09c653, 09c654, 09c655, 09c657, 09c667, 09c668, 09c669, 09c670, 09c676, 09c694, and 09i31.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
As the subbottom 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 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 and 9-m offsets between the Chirp and GPS antenna. Refer to figures 1A and 1B included with this archive (Data Series 590) for a diagram of the acquisition geometries, including the GPS offset measurements. Line navigation maps and interactive profiles generated with CTI SonarWeb v. 3.16.0096 PRO software have been corrected for the GPS offsets.
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
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 should be recorded in the logbooks and is evident on the subbottom profiles by steep, abrupt shifts in the seafloor return.
Lineage:
Process_Step:
Process_Description:
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 many lines; consequently, they were renumbered to start at 1 (this was achieved by using the trace sequence number within line [tracl] header values instead of the recorded shot values) during post-processing with SU. These corrected SEG-Y files are included in this archive.
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 and converting channel 0 for each shot to SU format, (2) applying automatic gain control, (3) displaying PostScript, (4) converting of PostScript image to a GIF image (including a thumbnail image), and (5) saving gained data in SEG-Y format. For additional SU processing and script details, please refer to <https://pubs.usgs.gov/ds/590/software/su/readme.txt>
All the processed SEG-Y data were then exported to CTI SonarWeb v. 3.16.0096 PRO software to produce a geospatially interactive version of each profile that allows the user to obtain a geographic location and depth for a cursor position on the profile. Refer to the Supplemental Information section above for details on how to use the geospatial profiles.
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 comma-delimited text files (for use with ESRI software), one containing unique shotpoint positions (09cct03.txt, 09cct03a.txt, and 09cct04.txt) and another containing the 1,000 shot interval locations (s09cct03.txt, s09cct03a.txt, and s09cct04.txt); all can be viewed within the nav folder; refer to the Browse_Graphic section above for details.
Process_Date: 2009
Process_Step:
Process_Description:
All concatenated, comma-delimited text files were imported into ArcGIS 9.3 (Build 1770) and saved as either a point or polyline file in the ESRI shapefile format.
Process_Date: 2009
Process_Step:
Process_Description:
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. 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.
Process_Date: 2009
Process_Step:
Process_Description:
Trackline map editing: The trackline maps were exported to Adobe Illustrator v. 12.0.1 for additional editing and later converted into JPEG format by Adobe GoLive v. 8.0.1.
Process_Date: 2009
Process_Step:
Process_Description:
Line navigation map creation: A map of trackline navigation for each subbottom profile was also produced with CTI SonarWeb v. 3.16.0096 PRO software.
Process_Date: 2009
Process_Step:
Process_Description:
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.
Process_Date: 2010
Spatial_Data_Organization_Information:
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.
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Geographic:
Latitude_Resolution: 0.000001
Longitude_Resolution: 0.000001
Geographic_Coordinate_Units: decimal degrees
Geodetic_Model:
Horizontal_Datum_Name: WGS84
Ellipsoid_Name: WGS_1984
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.25722356300
Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label:
09cct03.txt, s09cct03.txt, and 09cct03_s.txt; 09cct03a.txt, s09cct03a.txt, and 09cct03a_s.txt; 09cct04.txt, s09cct04.txt, and 09cct04_s.txt
Society of Exploration Geophysicists (SEG)-Y headers (<http://www.seg.org/>).
Attribute:
Attribute_Label: FID*
Attribute_Definition: Internal feature number.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: Shape*
Attribute_Definition: Feature geometry.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain: Coordinates defining the features.
Attribute:
Attribute_Label: UTMX
Attribute_Definition: UTM-X coordinate (Zone 16)
Attribute_Definition_Source: Universal Transverse Mercator Geographic Coordinate System
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 300696
Range_Domain_Maximum: 388062
Attribute:
Attribute_Label: UTMY
Attribute_Definition: UTM-Y coordinate (Zone 16)
Attribute_Definition_Source: Universal Transverse Mercator Geographic Coordinate System
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 3341355
Range_Domain_Maximum: 3358278
Attribute:
Attribute_Label: Line
Attribute_Definition: Trackline number
Attribute_Definition_Source: U.S. Geological Survey
Attribute_Domain_Values:
Unrepresentable_Domain: Trackline name - 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), '##' 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.
Attribute:
Attribute_Label: Shot
Attribute_Definition: Shotpoint number
Attribute_Definition_Source: U.S. Geological Survey
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 1
Range_Domain_Maximum: 20000
Attribute:
Attribute_Label: Lon
Attribute_Definition: Longitude (decimal degrees)
Attribute_Definition_Source: World Geodetic System 1984 Geographic Coordinate System
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: -89.167867
Range_Domain_Maximum: -89.035461
Attribute:
Attribute_Label: Lat
Attribute_Definition: Latitude (decimal degrees)
Attribute_Definition_Source: World Geodetic System 1984 Geographic Coordinate System
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 30.268000
Range_Domain_Maximum: 30.187328
Attribute:
Attribute_Label: YEAR
Attribute_Definition: Year
Attribute_Definition_Source: U.S. Geological Survey
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 2009
Range_Domain_Maximum: 2009
Attribute:
Attribute_Label: DOY:HR:MIN:SEC
Attribute_Definition: Day of year:hour:minute:second
Attribute_Definition_Source: Coordinated Universal Time
Attribute_Domain_Values:
Unrepresentable_Domain: Day of year, hour, minute and second of data acquisition
Overview_Description:
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 0.021 to 385 MB for 09CCT03 and 2 to 193 MB for 09CCT04.
Entity_and_Attribute_Overview:
Graphic image file: Printable versions of the subbottom 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 printable subbottom profiles images.
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 remaining attributes listed in the above section that do not have an accompanying asterisk are found in 09cct03.txt, s09cct03.txt, and 09cct03_s.txt; 09cct03a.txt, s09cct03a.txt, and 09cct03a_s.txt; 09cct04.txt, s09cct04.txt, and 09cct04_s.txt
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.
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/>.
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>
Contact_Instructions: All of this report except the SEG-Y files is available on-line.
Resource_Description: U.S. Geological Survey Data Series 590
Distribution_Liability:
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.
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: SEG-Y
Format_Information_Content:
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 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.
File_Decompression_Technique: None
Transfer_Size: 19.2 GB
Digital_Transfer_Option:
Offline_Option:
Offline_Media: DVD
Recording_Format: ISO 9660
Compatibility_Information: Unix, Linux, DOS, Macintosh
Digital_Form:
Digital_Transfer_Information:
Format_Name: map document, shapefile, metadata
Format_Information_Content:
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 ESRI desktop software including their free software, ArcGIS Explorer (<http://www.esri.com/software/arcgis/explorer/>), or GeoMapApp (<http://www.geomapapp.org/>) software, which is compatible with all platforms.
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).
Technical_Prerequisites:
Use of SEG-Y data requires specialized seismic processing software, such as public domain software Seismic Unix (<http://www.cwp.mines.edu/cwpcodes/>).
U.S. Department of the Interior |
U.S. Geological Survey