Archive of Chirp Subbottom Profile, Imagery, and Geospatial Data Collected in 2021 Near Pensacola Beach, Florida

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  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?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Forde, Arnell S., 20220503, Archive of Chirp Subbottom Profile, Imagery, and Geospatial Data Collected in 2021 Near Pensacola Beach, Florida:.

   This is part of the following larger work.
   Forde, Arnell S., DeWitt, Nancy T., and Flocks, James G., 20220503, Archive of Chirp Subbottom Profile and Single-Beam Bathymetry Data Collected in 2021 From Santa Rosa Island, Florida: U.S. Geological Survey data release doi:10.5066/P9VRSD9J, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P9VRSD9J

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -87.36180
   East_Bounding_Coordinate: -87.16920
   North_Bounding_Coordinate: 30.34120
   South_Bounding_Coordinate: 30.27280
   

3. What does it look like?
4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 02-Jun-2021

   Ending_Date: 09-Jun-2021

   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 0.0197875056. Longitudes are given to the nearest 0.0227943825. 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?

   2021-322-FA_nav.csv (493434 data records), 2021-322-FA_1000sht.csv (458 data records), 2021-322-FA_sol.csv (91 data records).

   These files, which are located in 2021-322-FA_nav.zip, represent the June 2021 subbottom navigation data. The attributes described below are for the survey's shotpoint navigation file, 2021-322-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:	465216.59
   Maximum:	483734.39
   Units:	meters

   UTMY

   UTM-Y coordinate (Zone 16N) (Source: Universal Transverse Mercator Coordinate System)

   Range of values
   Minimum:	3349049.293
   Maximum:	3356611.581
   Units:	meters

   Line

   Trackline name (Source: U.S. Geological Survey) Line numbers were automatically assigned by the EdgeTech 3400 chirp topside unit during data acquisition and are composed of sequentially increasing numbers. Lines that were collected inshore are denoted by the addition of a prefix, "inshore" or "inshore_", immediately before the line number. If recording was prematurely terminated or reran, due to quality or acquisition issues, sequentially increasing numbers, beginning at .001, were appended to the trackline name (for example, 1.001, 1.002, etc.).

   Shot

   Shotpoint number (Source: U.S. Geological Survey)

   Range of values
   Minimum:	1
   Maximum:	20507

   Lon

   Longitude (decimal degrees) (Source: World Geodetic System 1984 Geographic Coordinate System)

   Range of values
   Minimum:	-87.361772
   Maximum:	-87.169178
   Units:	decimal degrees

   Lat

   Latitude (decimal degrees) (Source: World Geodetic System 1984 Geographic Coordinate System)

   Range of values
   Minimum:	30.272756
   Maximum:	30.341225
   Units:	decimal degrees

   YEAR

   Year of data acquisition (Source: U.S. Geological Survey)

   Range of values
   Minimum:	2021
   Maximum:	2021

   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 2021-322-FA_nav.zip (Forde and others, 2022) 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 (91 files). These files have a .sgy extension and range in size from 1.9 to 124 MB. These data are included in the download file, 2021-322-FA_segy.zip, 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 (91 files) and are included in the download file, 2021-322-FA_seisimag.zip.

   Entity_and_Attribute_Overview:

   GIS file: The GIS data associated with this survey are provided as a compressed zip file, 2021-322-FA_gis.zip, which is composed of an Esri map document, shapefiles, individual shapefile metadata, a Google Earth KMZ file, a folder of processed subbottom profile images, 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. The authors thank Jake Fredericks (former employee) of the USGS for his assistance in data collection and piloting the R/V (Research Vessel) Sallenger. This document was improved by scientific/editorial and metadata reviews from Emily Wei and Breanna Williams of the 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?

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: 02-Jun-2021 (process 1 of 4)

   Chirp acquisition - Subbottom data were acquired from the chirp towfish, which was towed by the 26-foot research vessel, the R/V Sallenger and positioned approximately 1 m below the water surface. 95 lines, equivalent to a total of 219 line-kilometers, were surveyed. The seismic source utilized during 2021-322-FA was a rental unit from Echo81 that consisted of an EdgeTech SB-3400 towfish running DISCOVER version 4.09 acquisition software and towed on the port side of the R/V Sallenger, approximately 3 m behind the GPS reference point. The data were acquired at 5 hertz (Hz), which equates to a 0.2 s sample interval, using a frequency sweep of 3-8 kilohertz (kHz), and recording length was approximately 45.86 ms. Based on survey speeds of approximately 4 knots, the shot spacing is approximately 0.450 m. The binary portion of the seismic data 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) and geophysical logs are also provided as supplemental information in the download file, 2021-322-FA_logs.zip. 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: 05-Aug-2021 (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 profile), (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:

   • SEG-Y

   Data sources produced in this process:

   • SEG-Y.gif

   Date: 05-Aug-2021 (process 3 of 4)

   Navigation acquisition and processing - An Applanix POS MV IANS (positioned amidship) was used for positioning onboard the R/V Sallenger. Real-time positions from the POS MV were recorded and written to the seismic trace headers via a RS232 cable running from the POS MV receiver to the topside unit of the chirp system every second. 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) 2021-322-FA_nav.csv contains unique shotpoint positions (along each line) for the entire survey, (2) 2021-322-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) 2021-322-FA_sol.csv has the start-of-line locations for each trackline. The concatenated, comma-delimited text files were later imported into ArcGIS 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:

   • 1*-6*.txt; inshore*.txt

   Data sources produced in this process:

   • 2021-322-FA_nav.csv
   • 2021-322-FA_1000sht.csv
   • 2021-322-FA_sol.csv

   Date: 16-Feb-2022 (process 4 of 4)

   Trackline map creation - 2021-322-FA_location.mxd and associated shapefiles (.shp) were created with Esri ArcGIS 10.7 software. The survey navigation file, 2021-322-FA_nav.csv, was imported into ArcMap 10.7.1.11595 and processed using the ArcScript "Points to Line" to create a polyline shapefile of the cruise tracklines called 2021-322-FA_trkln. The 1,000-shot-interval and start-of-line files, 2021-322-FA_1000sht.csv and 2021-322-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 .mxd document to keyhole markup language (.kml) format prior to them being compressed 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 ArcGIS 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 2021-322-FA_gis.zip. 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:

   • 2021-322-FA_nav.csv
   • 2021-322-FA_1000sht.csv
   • 2021-322-FA_sol.csv

   Data sources produced in this process:

   • 2021-322-FA_trkln.shp
   • 2021-322-FA_shots.shp
   • 2021-322-FA_sol.shp
   • 2021-322-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:

   • https://doi.org/10.1190/1.1440530

   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:

   • https://github.com/JohnWStockwellJr/SeisUnix

   Farmer, A.S., Fredericks, J.J., and Flocks, J.G., 20201006, Coastal Coastal multibeam bathymetry data collected in 2019 off of Santa Rosa Island, Florida: U.S. Geological Survey data release doi:10.5066/P9IKP27T, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P9IKP27T

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. All lines were acquired with a deep-water delay of 1 ms recorded to the headers. The cause of this issue is unknown but the survey's Electronics Technician, Jake Fredericks, assumed it was attributable to the dual-frequency setting on the EdgeTech SB-3400 rental unit. This deep-water delay was removed during processing by A. Forde; all the corrected SEG-Y files are provided in Forde and others (2022).
2. How accurate are the geographic locations?
   As the subbottom profile data were acquired, the position of the vessel was continuously determined by an Applanix POS MV Wavemaster II inertial aided navigation system (IANS), which is accurate to within 0.5-2 meters (m). To ensure consistent spacing between survey lines acquired aboard the R/V Sallenger, pre-determined trackline locations were imported into HYPACK 2021 navigation software and followed during seismic data collection. During acquisition, positions from the POS MV IANS were recorded and written to seismic trace headers in arcseconds every 1 second (s) and were subsequently converted to latitude and longitude coordinates (World Geodetic System of 1984, WGS84, realization G1762). The approximate 3-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. TWT times shown on the printable profile images are relative to the chirp towfish position (just below the sea surface), not to the sea surface.
4. Where are the gaps in the data? What is missing?
   A total of 95 seismic lines were collected during this field activity, but only 91 were processed. Lines 3.008, 4.002, and inshore_4A were partial lines (< 1 megabyte [MB]) containing no usable data and inshore2A was corrupted during acquisition; consequently, all these lines were excluded from this data release (Forde and others, 2022). For line inshore1, the number of samples was changed (from 1318 to 2290) during recording, which resulted in an issue with the original file. Using the topside unit, the line was played back until shot 1290 and saved (with a shorter two-way travel (TWT) time (~25 ms) than all other lines). This line was processed successfully and has been included in Forde and others (2022).
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?

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?
   • Availability in digital form:

     Data format:	The ZIP file contains the SEG-Y data and support information. in format SEG-Y (version Revision 0) Size: 2320
     Network links:	https://coastal.er.usgs.gov/data-release/doi-P9VRSD9J/data/2021-322-FA_segy.zip

     Data format:	The ZIP file contains the survey navigation data and support information. in format Comma-delimited ASCII Size: 4.2
     Network links:	https://coastal.er.usgs.gov/data-release/doi-P9VRSD9J/data/2021-322-FA_nav.zip

     Data format:	The ZIP file contains the survey navigation data represented geospatially as GIS files, a folder of processed subbottom profile images (accessible via hyperlinks included in the MXD), and support information. in format Shapefile, MXD, KMZ, GIF Size: 50.5
     Network links:	https://coastal.er.usgs.gov/data-release/doi-P9VRSD9J/data/2021-322-FA_gis.zip

     Data format:	The ZIP file contains images of the processed subbottom profile data and support information. in format GIF Size: 47.1
     Network links:	https://coastal.er.usgs.gov/data-release/doi-P9VRSD9J/data/2021-322-FA_seisimag.zip

   • Cost to order the data: None

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: 03-May-2022

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)