Archive of Chirp Subbottom Profile, Imagery, and Geospatial Data Collected in 2022 Offshore of Breton Island, Louisiana

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Frequently anticipated questions:

What does this data set describe?

Title:
Archive of Chirp Subbottom Profile, Imagery, and Geospatial Data Collected in 2022 Offshore of Breton Island, Louisiana
Abstract:
On August 5, 2022, researchers from the U.S. Geological Survey (USGS) conducted an offshore geophysical survey to map the shoreface and determine Holocene stratigraphy near Breton Island, Louisiana (LA). The Breton Island Post Construction Monitoring project objective includes the investigation of nearshore geologic controls on surface morphology in addition to mapping the seafloor to evaluate coastal change. This publication (Forde and others, 2023) serves as an archive of high-resolution chirp subbottom trace data, survey trackline map, navigation files, geographic information system (GIS) data, and formal Federal Geographic Data Committee (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM). Processed subbottom profile images are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y revision 0 format (Barry and others, 1975). In addition to this data release, the SEG-Y files can be downloaded from the USGS Coastal and Marine Geoscience Data System (CMGDS) at, https://cmgds.marine.usgs.gov.
Supplemental_Information:
Chirp systems use a signal of continuously varying frequency; the system used during this survey produces high-resolution, shallow-penetration (typically less than 75-milliseconds [ms]) profile images of sub-seafloor stratigraphy. The towfish contains a transducer that transmits and receives acoustic energy and is typically towed 1–2 meters (m) below the sea's surface. As transmitted acoustic energy intersects density boundaries, such as the seafloor or sub-surface sediment layers, energy is reflected 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 (2D) image of the shallow geologic structure beneath the towfish is produced.
  1. How might this data set be cited?
    Forde, Arnell S., 20231101, Archive of Chirp Subbottom Profile, Imagery, and Geospatial Data Collected in 2022 Offshore of Breton Island, Louisiana:.

    This is part of the following larger work.

    Forde, Arnell S., Flocks, James G., and Farmer, Andrew S., 20231101, Archive of Chirp Subbottom Profile Data Collected in 2022 From Breton Island, Louisiana: U.S. Geological Survey data release doi:10.5066/P9Q28MFD, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -89.13140
    East_Bounding_Coordinate: -89.09300
    North_Bounding_Coordinate: 29.48070
    South_Bounding_Coordinate: 29.45830
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 05-Aug-2022
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: SEG-Y, 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?
      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 0.0197905763. Longitudes are given to the nearest 0.0226039207. Latitude and longitude values are specified in Decimal Degrees. The horizontal datum used is WGS_1984.
      The ellipsoid used is WGS_84.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
  7. How does the data set describe geographic features?
    2022-328-FA_nav.csv (102329 data records), 2022-328-FA_1000sht.csv (82 data records), 2022-328-FA_sol.csv (46 data records).
    These files, which are located in 2022-328-FA_nav.zip (Forde and others, 2023), represent the August 2022 subbottom navigation data. The attributes described below are for the survey's shotpoint navigation file, 2022-328-FA_nav.csv. For detailed information specific to the ArcGIS data, please see the associated shapefile metadata. (Source: U.S. Geological Survey)
    UTMX
    UTM-X coordinate (Zone 16N) (Source: Universal Transverse Mercator Coordinate System)
    Range of values
    Minimum:293317.012
    Maximum:297048.59
    Units:meters
    UTMY
    UTM-Y coordinate (Zone 16N) (Source: Universal Transverse Mercator Coordinate System)
    Range of values
    Minimum:3260639.805
    Maximum:3263096.896
    Units:meters
    Line
    Trackline name (Source: U.S. Geological Survey) Line numbers were automatically assigned by the EdgeTech 3100P chirp topside unit during data acquisition. Trackline names consist of sequentially increasing numbers, with the survey date (20220805) serving as a prefix that is followed by a UTC timestamp (for example, 134905) corresponding to when the line was collected.
    Shot
    Shotpoint number (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:6231
    Lon
    Longitude (decimal degrees) (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:-89.131444
    Maximum:-89.093025
    Units:decimal degrees
    Lat
    Latitude (decimal degrees) (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:29.458328
    Maximum:29.480694
    Units:decimal degrees
    YEAR
    Year of data acquisition (Source: U.S. Geological Survey)
    Range of values
    Minimum:2022
    Maximum:2022
    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, in Coordinated Universal Time (UTC).
    Entity_and_Attribute_Overview:
    Navigation file: Navigation files are available as ASCII delimited text files in comma-separated values (CSV) file format. The final navigation files are provided in 2022-328-FA_nav.zip (Forde and others, 2023) and represent the reprojected survey shotpoint navigation, 1,000-shot-interval locations, and start of line files.
    Entity_and_Attribute_Overview:
    Binary data file: Seismic trace data are available as binary files in SEG-Y format (46 files). These files have a .sgy extension and range in size from 2.9 to 95.5 MB. These data are included in the download file, 2022-328-FA_segy.zip (Forde and others, 2023), and can also be found by going to the USGS CMGDS at, https://cmgds.marine.usgs.gov. The SEG-Y rev. 0 format (Barry and others, 1975) data 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.
    Entity_and_Attribute_Overview:
    Graphic image file: Printable versions of the processed subbottom profiles are available as GIF images (46 files) and are included in the download file, 2022-328-FA_seisimag.zip.
    Entity_and_Attribute_Overview:
    GIS file: The GIS data associated with this survey are provided as a compressed zip file, 2022-328-FA_gis.zip (Forde and others, 2023), which is composed of an Esri map document, shapefiles, individual shapefile metadata, a Google Earth KMZ file, a folder of processed subbottom profile images, survey area map, and a readme file.
    Entity_and_Attribute_Detail_Citation:
    The entity and attribute information were generated by the individual and (or) agency identified as the originator of the dataset. Please review the rest of the metadata record for additional details and information.

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
  2. Who also contributed to the data set?
    Funding and (or) support for this study were provided by the USGS Coastal and Marine Hazards and Resources Program. This document was improved by scientific/editorial and metadata reviews from Lesley Quezergue of the Bureau of Ocean Energy Management and Tess Rivenbark-Terrano and St. Petersburg Coastal and Marine Science Center.
  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?

The purpose of this data release is to archive digital chirp subbottom profile data and associated files collected during USGS Field Activity Number 2022-328-FA. Additional survey and data details are available from the USGS CMGDS at, https://cmgds.marine.usgs.gov/fan_info.php?fan=2022-328-FA.

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: 05-Aug-2022 (process 1 of 4)
    Chirp acquisition - Subbottom data were acquired from the chirp towfish, which was towed by the 26-foot research vessel R/V Sallenger and positioned approximately 1 m below the water surface. The seismic source utilized during 2022-328-FA was an EdgeTech SB-424 running DISCOVER version 10 acquisition software and towed on the port side of the vessel, approximately 3.4 m behind the GNSSS reference point. 46 lines, equivalent to a total of 49.75 line-kilometers, were surveyed. The data were acquired at 5 hertz (Hz), which equates to a roughly 0.2 s sample interval, using a frequency sweep of 2-15 kilohertz (kHz), and recording length was 173.42 ms. Based on survey speeds of about 4 knots, the shot spacing is approximately 0.450 m. The binary portion of the seismic data provided in Forde and others (2023) is stored in SEG-Y rev. 0, IBM 32-bit float [big-endian byte order] 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 ASCII format instead of Extended Binary Coded Decimal Interchange Code (EBCDIC) format. The SEG-Y formatted trace files have a .sgy extension and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). The printable profiles provided are chirp subbottom profile images that were processed using SU software. Survey Field Activity Collection System (FACS) logs, acquisition geometry, and geophysical operations log are also provided as supplemental information in the download file, 2022-328-FA_logs.zip (Forde and others, 2023). Person who carried out this activity:
    James G. Flocks
    U.S. Geological Survey
    Research Geologist
    600 4th Street South
    St. Petersburg, FL

    (727) 502-8000 (voice)
    jflocks@usgs.gov
    Date: 12-Jan-2023 (process 2 of 4)
    Chirp processing - The SEG-Y data were processed with Seismic Unix (Release 44) software to produce gained Graphics Interchange Format (GIF) images of the subbottom profiles included in this data release. A representative chirp data processing sequence consisted of (1) removing raw [vessel] navigation data for each shot and converting the SEG-Y file to SU format, (2) applying automatic gain control, (3) trimming the trace data TWT to 30 ms (no observable features, aside from multiples, were encountered below that point in the profiles), (4) generating a PostScript image of the traces, and (5) converting the PostScript image to a GIF image. 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:
    • *.sgy
    Data sources produced in this process:
    • *.gif
    Date: 12-Jan-2023 (process 3 of 4)
    Navigation acquisition and processing - A SP90M GNSS using a Spectra Precision GNSS (SPGA) receiver (positioned amidships) was used for positioning onboard the R/V Sallenger. Real-time positions from the SP90M were recorded and written to the seismic trace headers via a RS232 cable running from the SP90M receiver to the topside unit of the chirp system every 0.20 seconds. During subbottom processing, location data were extracted from the SEG-Y headers of the processed chirp profiles, using Seismic Unix (Cohen and Stockwell, 2010) software and output as ASCII text files; PROJ.5.1.0 (https://proj.org/) software was used to project WGS84 latitude and longitude coordinates to Universal Transverse Mercator (UTM) northings and eastings (WGS84, Zone 16 North [N], meters). Navigation files for each subbottom line, saved by line number, were concatenated into comma-delimited text files so they could be represented geospatially using Esri ArcGIS software. The final output files are as follows: (1) 2022-328-FA_nav.csv contains unique shotpoint positions (along each line) for the entire survey, (2) 2022-328-FA_1000sht.csv includes the 1,000-shot-interval locations that were generated to correlate shot locations on the trackline map with evenly spaced 1,000-shot index markers along the top of the printable profile images, and (3) 2022-328-FA_sol.csv has the start-of-line locations for each trackline. The concatenated, comma-delimited text files were later imported into ArcMap and saved as either a point or polyline file (in Esri's shapefile format) for use in the map document (.mxd) included in 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
    Data sources used in this process:
    • 2022*.txt
    Data sources produced in this process:
    • 2022-328-FA_nav.csv
    • 2022-328-FA_1000sht.csv
    • 2022-328-FA_sol.csv
    Date: 26-Apr-2023 (process 4 of 4)
    Trackline map creation - 2022-328-FA_location.mxd and associated shapefiles (.shp) were created with Esri ArcMap 10.8.2 software. The survey navigation file, 2022-328-FA_nav.csv, was imported into ArcMap and processed using the ArcScript "Points to Line" to create a polyline shapefile of the cruise tracklines called 2022-328-FA_trkln.shp. The 1,000-shot-interval and start-of-line files, 2022-328-FA_1000sht.csv and 2022-328-FA_sol.csv, were imported into ArcMap and saved as point shapefiles. A non-proprietary version of the location map was created by utilizing the ArcToolbox "Map to KML" tool, which converted each layer included in the map document (.mxd) to keyhole markup language (.kml) format prior to them being compressed (zipped) and saved as a .kmz file. The ArcGIS and Google Earth geospatial files provided in this publication are unprojected (geographic coordinates, WGS84). For detailed information about the GIS files provided in this data release, please refer to the individual metadata records (*_metadata.txt and *.shp.xml) accompanying each shapefile and the readme file included in 2022-328-FA_gis.zip (Forde and others, 2023). 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:
    • 2022-328-FA_nav.csv
    • 2022-328-FA_1000sht.csv
    • 2022-328-FA_sol.csv
    Data sources produced in this process:
    • 2022-328-FA_trkln.shp
    • 2022-328-FA_shots.shp
    • 2022-328-FA_sol.shp
    • 2022-328-FA.kmz
  3. What similar or related data should the user be aware of?
    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
    Cohen, J.K., and Stockwell, J.W., Jr., 2010, Seismic Un*x Release No. 44: An open source software package for seismic research and processing: Center for Wave Phenomena, Colorado School of Mines, Golden, Colorado.

    Online Links:

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 dependent on equipment and operating condition variables.
  2. How accurate are the geographic locations?
    Location information associated with each seismic profile was determined by a SP90M global navigation satellite system (GNSS) receiver positioned aboard the R/V Sallenger, where pre-determined trackline locations were imported into HYPACK 2021 navigation software and followed during seismic data collection. During acquisition, positions from the SP90M GNSS receiver located on the R/V Sallenger were recorded and written to seismic trace headers in arcseconds every 0.20 s and were subsequently converted to latitude and longitude coordinates (World Geodetic System of 1984, WGS84). The approximately 3.4-m offset between the chirp shot position and ship's global positioning system (GPS) antenna reference point were not accounted for during acquisition, nor have the American Standard Code for Information Interchange (ASCII) navigation files and trackline map 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 times (TWT) shown on the printable profile images are relative to the chirp towfish position (below the sea surface), not to the sea surface.
  4. Where are the gaps in the data? What is missing?
    A total of 46 seismic lines were collected during this field activity are included in this data release (Forde and others, 2023).
  5. How consistent are the relationships among the observations, including topology?
    These datasets are 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 Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. 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 S. Forde
    U.S. Geological Survey
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    aforde@usgs.gov
    Contact_Instructions:
    The SEG-Y files included in this data release are also downloadable from the Coastal and Marine Geoscience Data System at, https://cmgds.marine.usgs.gov.
  2. What's the catalog number I need to order this data set?
  3. What legal disclaimers am I supposed to read?
    This publication was prepared by an agency of the United States Government. Although these data were 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?
  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 (https://github.com/JohnWStockwellJr/SeisUnix).

Who wrote the metadata?

Dates:
Last modified: 25-Oct-2023
Metadata author:
Arnell S. 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/2022-328-FA_metadata.faq.html>
Generated by mp version 2.9.51 on Wed Nov 1 14:59:11 2023