In June of 2007, the U.S. Geological Survey (USGS), in cooperation with the Louisiana Department of Natural Resources (LDNR), conducted a geophysical survey offshore of the Chandeleur Islands, Louisiana. 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.
Purpose:
The data archived here were collected as part of the USGS Barrier Island Comprehensive Monitoring (BICM) project, which is part of a broader study focused on Subsidence and Coastal Change. The purpose of the study was to investigate the shallow geologic framework and monitor the enviromental impacts of Hurricane Katrina (Louisiana landfall was on August 29, 2005) on the Gulf Coast's barrier island chains.
Supplemental_Information:
The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 07SCC01 tells us the data were collected in 2007 for the Subsidence and Coastal Change (SCC) study and the data were collected during the first 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 trackline 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 SB-424 and i for SB-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.
The Chirp systems used a signal of continuously varying frequency. The towfish is the 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 sub-bottom 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 sub-bottom source employed for Chirp data collection, during this cruise, consisted of an EdgeTech (FSSB) XStar SB-424 and SB-512i towfish running Triton Imaging SB Logger V. 1.6.4.37.73 acquisition software that was towed about 5.83 m behind the GPS antenna. The frequency range was 4 - 16 kHz (SB-424) and from 0.5 - 8 kHz to 0.5 - 6 kHz (SB-512i). Sample frequencies of the data for the 512i and 424 were 21 and 25 kHz, respectively, and record length was approximately 50 ms. A total of 2 lines were collected using the 424 system and 47 were collected with the 512i.
For each recorded shot of the Chirp data, 3 channels of trace data are collected. 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. Only channel 0 was used to produce the profiles presented here. However, all channels are included in the SEG-Y data files.
The archived trace data are in standard SEG-Y rev 1, 4-byte integer, IBM float format (Norris and Faichney, 2002); an ASCII format is used for the first 3,200 bytes of the card image header instead of the SEG-Y rev 0 (Barry and others, 1975) EBCDIC format. The SEG-Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) Release 41 (Cohen and Stockwell, 2005). 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 version 3.16.0096 PRO software to produce an 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. NOTE: The only supported Web browsers that properly display all features of the interactive profiles are Internet Explorer 8 or greater for Windows and Firefox 3.6 or greater for all platforms. For all 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>.
Post-processing of the data also revealed the first shot value recorded to the SEG-Y headers of lines 07i1, 07i4, 07i5, 07i7, 07i9, 07c14, 07c15, 07i16, 07i17, 07i18, 07i21, 07i22, 07i24, 07i27, 07i31, 07i32, 07i35, 07i36, 07i37, 07i40, 07i42, 07i45, 07i47 to be something other than one. A conversion program called Fixping V. 1.0.0 was used to correct this issue; these corrected SEG-Y files are provided in this archive.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20070602
Ending_Date: 20070613
Currentness_Reference: Data collection interval
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -89.300898
East_Bounding_Coordinate: -88.855756
North_Bounding_Coordinate: 30.148091
South_Bounding_Coordinate: 29.417192
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: Sub-bottom profile
Theme_Keyword: Seismic reflection
Theme_Keyword: Chirp
Theme_Keyword: Society of Exploration Geophysicists
Theme_Keyword: SEG-Y
Theme_Keyword: Subsidence and Coastal Change
Theme_Keyword: SCC
Theme_Keyword: 07SCC01
Theme_Keyword: Barrier Island Comprehensive Monitoring
Theme_Keyword: BICM
Place:
Place_Keyword_Thesaurus: Geographic Names Information System (GNIS) Content Charcterization
Place_Keyword: United States of America
Place_Keyword: Louisiana
Place_Keyword: Chandeleur Islands
Place_Keyword: Freemason Islands
Place_Keyword: New Harbor Islands
Place_Keyword: North Islands
Place_Keyword: South Islands
Place_Keyword: Chandeleur Sound
Place_Keyword: Breton 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 sub-bottom profile data collected during USGS field activity 07SCC01. This map was created at a scale of 1:1,000,000. Refer to the Lineage section below for the trackline map creation process and other details.
Trackline map of digital sub-bottom profile data collected around the northern Chandeleur Islands (refer to Northern Islands area on the location map) during USGS field activity 07SCC01. This map was created at a scale of 1:250,000.
Trackline map of digital sub-bottom profile data collected around the southern Chandeleur Islands (refer to Southern Islands area on the location map) during USGS field activity 07SCC01. This map was created at a scale of 1:215,000.
Processed 1,000 shotpoint navigation file for all tracklines collected during field activity 07SCC01.
Browse_Graphic_File_Type: ASCII Text File
Data_Set_Credit:
Funding for this study was provided by the LDNR and USGS CMGP. We thank R/V G.K. Gilbert captain Richard Young of the USGS in St. Petersburg, FL, for his assistance in data collection. This document was improved by the reviews of Jordan Sanford (USGS) and Jamie Bonisteel-Cormier (Jacobs Technology Inc.) of the USGS St. Petersburg Coastal and Marine Science Center.
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
The validity or accuracy of marine sub-bottom 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. Minor anomalies include a distortion in the profile image after shot 1500 of line 07i20 (this was due to interference in the acquisition system introduced by a nearby thunderstorm) and lines 07c14, 07c15, and 07i40 (the interference was of unknown origin). During data collection, the frequency range for lines 07i46 - 07i48 was changed from 0.5 - 8 kHz to 0.5 - 6 kHz; the effects of this change can be observed in both the water column and the subsurface of the profile.
Logical_Consistency_Report:
This dataset is from one field activity with consistent instrument calibrations. Tracklines 07i1 - 07i13 and 07i16 - 07i49 were collected using the EdgeTech SB-512i system. Tracklines 07c14 and 07c15 were collected using the EdgeTech SB-424 system.
Completeness_Report:
These data are collected along tracklines (2-D) and are therefore inherently incomplete. Geologic details between lines must be inferred.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
As the sub-bottom profiles were acquired, the position of the vessel was continuously determined by a Coda Octopus F190 DGPS 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 5.83-m offset between the Chirp and GPS antenna. Refer to figure 1 included with this archive (Data Series 553) for a diagram of the acquisition geometry, including the GPS offset measurements. Line navigation maps and interactive profiles generated with CTI SonarWeb software have been corrected for the GPS offset.
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 sub-bottom profiles by steep, abrupt shifts in the seafloor return.
Lineage:
Process_Step:
Process_Description:
SEG-Y header processing: All erroneous lines were first processed with FixPing V.1.0.0 software to correct first shot values that were other than 1 within the trace headers. These corrected SEG-Y files are included in this archive.
Process_Date: 2007 and 2010
Process_Step:
Process_Description:
Chirp processing: The SEG-Y data were processed with Seismic Unix software 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 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. For additional SU processing and script details, please refer to <https://pubs.usgs.gov/ds/553/software/su/readme.txt>
All the processed SEG-Y data were later exported to CTI SonarWeb V.3.16.0096 PRO software to produce an interactive, geospatial 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.
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 (07scc01.txt) and another containing the 1,000 shot interval locations (s07scc01.txt); both can be viewed within the nav folder, refer to the Browse_Graphic section above for details.
NOTE: During data collection of line 07i47, the navigation system cable became disconnected from the acquisition system; consequently, no navigation data were collected between shot 584 and 9484 (an interval of approximately 30 minutes). [This line is displayed on the Northern Islands map as as dashed yellow line.] Due to the aforementioned error and the lack of other concurrently running acquisition systems, additional/replacement navigation could not be used and the shotpoint navigation processing script was unable to interpolate between points. Since discrete navigation fixes were not recorded for shots 1000 through 9000, only one latitude and longitude fix (from shotpoint 584), -88.952519, 30.140927, was associated with line 07i47 of the processed shotpoint navigation file.
Process_Date: 2007 and 2010
Process_Step:
Process_Description:
Both concatenated, comma-delimited text files were imported into ESRI ArcGIS 9.3 and saved as either a point (07scc01_shots.shp) or polyline (07scc01_tracklines.shp) file in the ESRI shapefile format.
Process_Date: 2007 and 2010
Process_Step:
Process_Description:
Trackline map creation: The trackline maps 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 V. 12.0.1 for further editing. The maps were later converted into JPEG format by Adobe GoLive 8.0.1. The maps are unprojected (geographic coordinates, NAD83). The coastline layer is a Louisiana Oil Spill Coordinator's Office (LOSCO) dataset. 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 V.3.16.0096 PRO software.
Process_Date: 2007 and 2010
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: North American Datum of 1983
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: 276868
Range_Domain_Maximum: 3320625
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: 3256523
Range_Domain_Maximum: 3336173
Attribute:
Attribute_Label: Line
Attribute_Definition: Trackline number
Attribute_Definition_Source: U.S. Geological Survey
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 07i01
Range_Domain_Maximum: 07i49
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: Geographic Coordinate System North American Datum of 1983
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: -89.274896
Range_Domain_Maximum: -88.856922
Attribute:
Attribute_Label: Lat
Attribute_Definition: Latitude (decimal degrees)
Attribute_Definition_Source: Geographic Coordinate System North American Datum of 1983
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 29.419127
Range_Domain_Maximum: 30.143049
Attribute:
Attribute_Label: YEAR
Attribute_Definition: Year
Attribute_Definition_Source: U.S. Geological Survey
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 2007
Range_Domain_Maximum: 2007
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 9 to 262 MB.
Entity_and_Attribute_Overview:
Graphic image file: Printable versions of the sub-bottom 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 asterick (*) 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 asterick are found in 07scc01.txt, s07scc01.txt, and 07scc01_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 sub-bottom research and processing, Center for Wave Phenomena, Colorado School of Mines. Available on-line at <http://www.cwp.mines.edu/cwpcodes/>.
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>
Zihlman, F.N., 1992, DUMPSEGY V1.0: A program to examine the contents of SEG-Y disk-image sub-bottom 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>.
Contact_Instructions: All of this report except the SEG-Y files is available on-line.
Resource_Description: U.S. Geological Survey Data Series 553
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 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 sub-bottom data samples that follow the trace identification header.
File_Decompression_Technique: None
Transfer_Size: 9.59 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 ESRI ArcGIS 9.3 software. The shapefiles provided may also be viewed using other versions of of ESRI desktop software including their free software, ArcGIS Explorer (http://www.esri.com/software/arcgis/explorer/), or GeoMapApp (<http://www.geomapapp.org/>).
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 sub-bottom processing software, such as public domain software Seismic Unix (<http://www.cwp.mines.edu/cwpcodes/>).
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U.S. Geological Survey