Chirp seismic reflection data- shotpoints, tracklines, profile images, and SEG-Y traces for EdgeTech 3400 chirp data collected in Nantucket Sound Massachusetts in the vicinity of Horseshoe Shoal during USGS field activity 2023-001-FA (point and polyline shapefiles, CSV text, PNG Images, and SEGY data, GCS WGS 84)

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Frequently anticipated questions:

What does this data set describe?

Title:
Chirp seismic reflection data- shotpoints, tracklines, profile images, and SEG-Y traces for EdgeTech 3400 chirp data collected in Nantucket Sound Massachusetts in the vicinity of Horseshoe Shoal during USGS field activity 2023-001-FA (point and polyline shapefiles, CSV text, PNG Images, and SEGY data, GCS WGS 84)
Abstract:
In May and June 2023, the U.S. Geological Survey, in collaboration with the Massachusetts Office of Coastal Zone Management, collected high-resolution geophysical and seafloor sampling data, in Nantucket Sound to understand the regional geology in the vicinity of Horseshoe Shoal. Geophysical data collected include swath bathymetry, backscatter, and seismic reflection profile data. Ground-truth data, including sediment samples, underwater video, and bottom photographs were also collected. This effort is part of a long-term collaboration between the USGS and the Commonwealth of Massachusetts to map the State’s waters. In addition to resolving coastal hazards, habitats and resources, these data can be used to better understand the Quaternary history of coastal Massachusetts including the influence of sea-level change and sediment supply on coastal evolution. This collaboration produces high-resolution geologic data that serve the needs of research, management, and the public. Data collected as part of this mapping cooperative continue to be released in a series of USGS Reports and Data Releases https://www.usgs.gov/centers/whcmsc/science/geologic-mapping-massachusetts-seafloor.
Supplemental_Information:
Support for 2023-001-FA was provided to the USGS from the Massachusetts Office of Coastal Zone Management. Approximately 441 linear kilometers of multibeam echosounder data, 400 km of seismic reflection profiling data were collected during 8 survey days along tracklines spaced 87 or 52 meters apart. Part 2 of this survey included ground validation using SEABOSS imagery and sediment samples collected at 59 stations covering both the 2022-001-FA and 2023-001-FA survey area. Data were collected using the R/V Rafael, owned and operated by the USGS Woods Hole Coastal and Marine Science Center. Additional information on both the 2022 and 2023 field activities are available from https://cmgds.marine.usgs.gov/services/activity.php?fan=2022-001-FA, https://cmgds.marine.usgs.gov/services/activity.php?fan=2023-001-FA
  1. How might this data set be cited?
    Baldwin, Wayne E., 20260521, Chirp seismic reflection data- shotpoints, tracklines, profile images, and SEG-Y traces for EdgeTech 3400 chirp data collected in Nantucket Sound Massachusetts in the vicinity of Horseshoe Shoal during USGS field activity 2023-001-FA (point and polyline shapefiles, CSV text, PNG Images, and SEGY data, GCS WGS 84): data release DOI:10.5066/P14NWTX8, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts.

    Online Links:

    This is part of the following larger work.

    Andrews, Brian D., Baldwin, Wayne E., Ackerman, Seth D., Worley, Charles R., Moore, Eric M., Nichols, Alex R., Berube, Patrick J., Huntley, Emily C., and Brothers, Laura L., 2026, High-resolution geophysical and sampling data collected in Nantucket Sound Massachusetts in the vicinity of Horseshoe Shoal, during USGS Field Activity 2023-001-FA: data release DOI:10.5066/P14NWTX8, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Andrews, B.D., Baldwin, W.E., Ackerman, S.D., Worley, C.R., Moore, E.M., Nichols, A.R., Berube, P.J., Huntley, E.C., and Brothers, L.L., 2026, High-resolution geophysical and sampling data collected in Nantucket Sound Massachusetts in the vicinity of Horseshoe Shoal, during USGS Field Activity 2023-001-FA: U.S. Geological Survey data release, https://doi.org/10.5066/P14NWTX8
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.481647
    East_Bounding_Coordinate: -70.324562
    North_Bounding_Coordinate: 41.584612
    South_Bounding_Coordinate: 41.525928
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/68b08553d4be021f0facf2cb?name=2023-001-FA_ET3400_browse.jpg (JPEG)
    Thumbnail image showing the extent of chirp seismic-reflection profile data collected within Nantucket Sound Massachusetts in the vicinity of Horseshoe Shoal, during USGS Field Activity 2023-001-FA.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 01-Jun-2023
    Ending_Date: 11-Jun-2023
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Shapefile, CSV, PNG Image, SEG-Y
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the 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 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 1/298.257224.
  7. How does the data set describe geographic features?
    2023-001-FA_ET3400_Tracklines.shp
    ET3400 Trackline shapefile for survey 2023-001-FA (98 polyline features). (Source: U.S. Geological Survey)
    FID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Coordinates defining the features.
    LineName
    Name of the trackline along which seismic-reflection data were collected in the format: Date and UTC time of file initiation time, as follows YYYYMMDD_HHMMSS (e.g.'20230601_134203'). (Source: U.S. Geological Survey) Character set
    ImageName
    PNG image name of seismic-reflection profile corresponding to survey trackline using the same naming convention as the attribute LineName. (Source: U.S. Geological Survey) Character set
    Shot_init
    Shot number at the start of the survey line. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:1
    Units:shot
    Resolution:1
    Shot_end
    Shot number at the end of the survey line. (Source: U.S. Geological Survey)
    Range of values
    Minimum:518
    Maximum:10567
    Units:shot
    Resolution:1
    Date
    Calendar month, day, and year at start of line as a text string in the format: MM/DD/YYYY. (Source: U.S. Geological Survey) Character set
    UTCDT_init
    Year, Julian day, and UTC time at the start of the survey line in the format: YYYY:JD:HH:MM:SS; Julian day is the integer number (although recorded here in text string format) representing the interval of time in days since January 1 of the year of collection. (Source: U.S. Geological Survey) Character set
    UTCDT_end
    Year, Julian day, and UTC time at the end of the survey line in the format: YYY:JD:HH:MM:SS; Julian day is the integer number (although recorded here in text string format) representing the interval of time in days since January 1 of the year of collection. (Source: U.S. Geological Survey) Character set
    SurveyID
    WHCMSC field activity identifier (e.g., "2023-001-FA" where 2023 is the survey year, 001 is survey number of that year, and FA is Field Activity). (Source: U.S. Geological Survey) Character set
    VehicleID
    Survey vessel name. (Source: U.S. Geological Survey) Character set
    DeviceID
    Sonar device used to collect seismic-reflection data. (Source: U.S. Geological Survey) Character set
    Length_km
    Length of seismic-reflection data line in kilometers (UTM Zone 19N, WGS 84) calculated in the SQLite database. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.366
    Maximum:8.216
    Units:kilometers
    Resolution:0.001
    2023-001-FA_ET3400_sht500.shp
    ET3400 500-interval shot point shapefile for survey 2023-001-FA (1186 point features). (Source: U.S. Geological Survey)
    FID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Coordinates defining the features.
    East
    Easting coordinate in UTM Zone 19 N meters, WGS 84 (Source: U.S. Geological Survey)
    Range of values
    Minimum:376419.33
    Maximum:389521.07
    Units:meters
    Resolution:.01
    North
    Northing coordinate in UTM Zone 19 N meters, WGS 84 (Source: U.S. Geological Survey)
    Range of values
    Minimum:4598075.82
    Maximum:4604560.01
    Units:meters
    Resolution:.01
    Lon
    Longitude coordinate in decimal degrees, WGS 84 (Source: U.S. Geological Survey)
    Range of values
    Minimum:-70.481647
    Maximum:-70.324562
    Units:degrees
    Resolution:1E-06
    Lat
    Latitude coordinate in decimal degrees, WGS 84 (Source: U.S. Geological Survey)
    Range of values
    Minimum:41.525928
    Maximum:41.584612
    Units:degrees
    Resolution:1E-06
    LineName
    Name of the trackline along which seismic-reflection data were collected in the format: Date and UTC time of file initiation time, as follows YYYYMMDD_HHMMSS (i.e.'20230601_134203'). (Source: U.S. Geological Survey) Character set
    ImageName
    PNG image name of seismic-reflection profile corresponding to survey line using the same naming convention as the attribute LineName. (Source: U.S. Geological Survey) Character set
    Shot
    Shot number (values are first, last, and every 500 shot between). (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:10567
    Units:shot
    Resolution:1
    Date
    Calendar month, day, and year at start of line as a text string in the format: MM/DD/YYYY. (Source: U.S. Geological Survey) Character set
    UTC_DT
    Year, Julian day, and UTC time for first, last, and every 500 shot point between of the survey line in the format: YYYY:JD:HH:MM:SS; Julian day is the integer number (although recorded here in text string format) representing the interval of time in days since January 1 of the year of collection. (Source: U.S. Geological Survey) Character set
    SurveyID
    WHCMSC field activity identifier (e.g. "2023-001-FA" where 2023 is the survey year, 001 is survey number of that year, and FA is Field Activity). (Source: U.S. Geological Survey) Character set
    VehicleID
    Survey vessel name. (Source: U.S. Geological Survey) Character set
    DeviceID
    Sonar device used to collect seismic-reflection data. (Source: U.S. Geological Survey) Character set
    NRP_Lon
    The longitude coordinate in decimal degrees, WGS 84 of the navigation reference point (GPS antenna) (Source: U.S. Geological Survey)
    Range of values
    Minimum:-70.481690
    Maximum:-70.324460
    Units:degrees
    Resolution:1E-06
    NRP_Lat
    The latitude coordinate in decimal degrees, WGS 84 of the navigation reference point (GPS antenna) (Source: U.S. Geological Survey)
    Range of values
    Minimum:41.525840
    Maximum:41.584517
    Units:degrees
    Resolution:1E-06
    2023-001-FA_ET3400_shtnav.csv
    ET3400 shot point comma separated values file for survey 2023-001-FA (521554 point features). (Source: U.S. Geological Survey)
    2023-001-FA_ET3400_Images
    Portable network graphic images of processed ET3400 profiles for survey 2023-001-FA (98 PNG images). (Source: U.S. Geological Survey)
    2023-001-FA_ET3400_SegyData
    SEG-Y format files of processed SB512i profiles for survey 2023-001-FA (98 SEG-Y files). (Source: U.S. Geological Survey)
    Entity_and_Attribute_Overview:
    The column headings and range domain values in '2023-001-FA_ET3400_shtnav.csv' match those in '2023-001-FA_ET3400_sht500.shp'. The PNG seismic reflection images can be hyperlinked to their corresponding trackline or shotpoint locations in a GIS using the shapefiles '2023-001-FA_ET3400_Tracklines.shp' or '2023-001-FA_ET3400_sht500.shp', respectively. The fist, last, and multiple of 500 shot features in '2023-001-FA_ET3400_sht500.shp' correspond to the x-axis ticks on the PNG images, which show two-way travel time (seconds) on the y-axis and distance along profile (annotation at 500 shot intervals) on the x-axis. The names of segy files included in 2023-001-FA_ET3400_SEG-Y.zip have the string 'proc-env' inserted between the profile line name and the .sgy extension to indicate that the files contain the processed envelope version of the traces.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Wayne E. Baldwin
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Wayne Baldwin
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    US

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

Why was the data set created?

This dataset contains shotpoint and trackline navigation, profile images, and processed SEG-Y trace data for approximately 400 km of EdgeTech 3400 chirp seismic-reflection data collected by the U.S. Geological Survey during USGS field activity 2023-001-FA in Nantucket Sound. Images of each seismic profile were generated in order to provide portable and easily viewable alternatives to the SEG-Y versions of the data. Each profile image can be hyperlinked to its corresponding trackline navigation contained within the Esri polyline shapefile '2023-001-FA_ET3400_Tracklines.shp'. Shotpoint index and tick marks along the top of the PNG images correlate to the positions of 500 shot intervals within the Esri point shapefile '2023-001-FA_ET3400_sht500.shp'. This information allows for spatial correlation of chirp seismic-reflection profiles images with other geophysical and sample data for investigating sea-floor morphology and stratigraphy in the area.

How was the data set created?

  1. From what previous works were the data drawn?
    JSF 3400 chirp data (source 1 of 1)
    U.S. Geological Survey, unpublished material, 3400 chirp JSF trace data.

    Type_of_Source_Media: disc
    Source_Contribution:
    The EdgeTech 3400 subbottom profiler was towed from the port side davit of the R/V Rafael. The towfish was suspended ~ 1 m below the water line from a catamaran float and towed approximately 13 meters astern of the DGPS antenna mounted on the after end of the cabin while underway. Chirp seismic data were collected using the EdgeTech 3400 sub-bottom profiling system topside acquisition and towfish. EdgeTech Discover Subbottom (version 41.0.1.116) seismic acquisition software was used to control the topside unit, digitally log three trace data (envelope, real, and imaginary) in the JSF and SEG-Y Rev. 1 (IEEE floating point) formats, and record DGPS navigation coordinates to the trace headers (in arc seconds of Latitude and Longitude, multiplied by a scalar of 100). JSF files contain header values for latitude, longitude, ffid, year, Julian Day, UTC time, and towfish heave, pitch, roll, and pressure depth. Data were acquired using 25-ms shot rates, a 20-ms pulse length, and a 3 to 12 kHz frequency sweep. Traces were recorded with a 20-microsecond sample interval and trace lengths of 100 ms.
  2. How were the data generated, processed, and modified?
    Date: Oct-2024 (process 1 of 4)
    PROCESS STEP 1: NAVIGATION EXTRACTION, TOWFISH LAYBACK CALCULATION, RAW TRACE IMPORT
    jsf2segy (version 5) and a iPython jupyter notebook, and Shearwater Reveal (version 2023) were used to process JSF data, extract navigation data, and calculate towfish layback position. The processing flows are summarized in the following steps.
    (1.) ‘jsf2segy’ was used to create SEG-Y files containing the real chirp traces from the JSF files. Option '-x' extracted real values from Analytic subbottom data, '-o' allowed writing real traces to an output .sgy file, and '-c' allowed writing a comma separated values (csv) file containing a JSF header values for latitude, longitude, ffid, year, Julian day, UTC time and towfish heave, pitch, roll, and pressure depth for use in additional processing.
    (2.) The output header csv files for each profile line were inspected for erroneous or absent navigation data. Profile line 20230601_152830 contained a section of missing navigation due to interruption of the GPS feed to Discover. A python Jupyter notebook utilized the python modules pandas (version 1.5.2), geopandas (version 0.12.1), pyproj (version 3.4.0), numpy (version 1.23.5), shapely (version 1.8.5.post1), and sqlite3 (version 3.40.0) to process the navigation data for each profile line in the following steps. The csv file was imported to a pandas dataframe. Appropriate time periods were extracted from Hypack raw files and merged by UTC time into the pandas dataframe of files with missing navigation sections. Navigation coordinates repeated over many traces because the DGPS sampling frequency was 1-Hz, while the chirp shot rate was 4-Hz. To account for this, duplicate latitude and longitude coordinate pairs in the dataframe were replaced by NAN values, while maintaining the first occurrence of a unique pair, as well as the last unique pair. The NAN values were replaced by coordinate pairs calculated through linear interpolation between the remaining unique pairs, resulting in unique navigation for every trace. The python function ShotlineLayback (developed by Nathan Miller of USGS-WHCMSC) computed layback navigation coordinates for the 3400 towfish. The algorithm used pyproj to transform the navigation reference point (nrp) coordinates from geographic (decimal degrees) to WGS84 UTM Zone 19 (meters), interpolated a sail line from the nrp coordinates along with a cumulative distance value, then computed layback positions for the 3400 shots by translating the nrp coordinates back along the sail line by the associated GPS to towfish offset value, and finally transformed the calculated layback UTM 19 coordinates back to geographic and wrote both set of coordinates to new data frame columns. A subset of the resulting dataframe consisting of values for layback easting and northing, layback latitude and longitude, profile line name, shot, UTC date/time, nrp longitude and latitude, as well as new fields populated for profile image name, survey ID, vehicle ID, and device ID was generated. The subset dataframe was written to a new 'layback-nav' csv file to be used in additional trace processing, then Geopandas and shapely were used to create a point geometry column from the layback geographic coordinates. SQL queries were used to load the navigation dataframe into a geospatial SQLite database using the pyspatialite interface. Records were appended to three database tables, the first containing the unique shot navigation, the second maintaining the first and last shots and even 500 shot intervals (which correspond to the annotation interval provided along the top of the seismic-reflection profile images), and the third containing trackline features created from the unique layback navigation point geometries.
    (3.) The Reveal flow ImportSegy consisted of the following steps for each seismic file. Input imported the raw real segy traces. DBMerge imported nrp and layback navigation from the 'layback-nav' csv file using the ffid field to merge. HeaderMath converted towfish depth in meters to milliseconds and heave in seconds to milliseconds. Header Filtering smoothed the towfish depth time series using a 31 trace boxcar filter. ApplyStatic shifted the traces by the smoothed towfish depth and heave static values. ObspyPicking used the threshold algorithm to predict the seafloor time and Header2Picks wrote the times to an output csv file for editing. Output wrote the traces to .seis (Reveal’s format) files for additional processing.
    These process steps and all subsequent process steps were conducted by the same person - Wayne Baldwin. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Wayne Baldwin
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA

    (508) 548-8700 x2226 (voice)
    (508) 457-2310 (FAX)
    wbaldwin@usgs.gov
    Data sources produced in this process:
    • Raw real trace seis files, nrp-nav csv files, seafloor time pick tables.
    Date: Oct-2024 (process 2 of 4)
    PROCESS STEP 2: NAVIGATION FEATURE CLASS GENERATION.
    The 500 shot and trackline tables were imported into QGIS (version 3.26) from the SQLite database, then exported (Right click on database feature class > Data > Save Features As) to the new Esri point and polyline shapefiles '2023-001-FA_ET3400_sht500.shp' and '2023-001-FA_ET3400_Tracklines.shp', respectively. Data sources produced in this process:
    • layback-nav csv files, navigation database tables, navigation feature classes.
    Date: Oct-2024 (process 3 of 4)
    PROCESS STEP 3: SEAFLOOR PICK EDITS, FINAL TRACE PROCESSING
    (1.) Using the Reveal 2D profile viewer, the seafloor predictions generated in step one were overlain on their associated seismic traces for quality control. The pick editor was used to eliminate or appropriately adjust erroneous times and edits were saved.
    (2.) The Reveal flow GainSegy consisted of the following steps for each seismic file. Input imported the raw real .seis file. Table2Header imported the edited seafloor picks replacing unedited header values. TraceMath applied a time varying gain to trace samples after the seafloor time (trace sample = trace sample * (trace sample time * 1000) ^ 0.7), and muted trace samples before the seafloor time. Output wrote the processed real traces to seis and SEG-Y files. Complex Trace Analysis (CTAN) computed envelope traces from the real, and finally Output wrote the processed envelope traces to seis and SEG-Y file. Data sources produced in this process:
    • edited seafloor time pick tables, processed real and envelope seis and segy trace files.
    Date: Oct-2024 (process 4 of 4)
    PROCESS STEP 4: DIAGNOSTIC SEISMIC PROFILE PLOTTING
    The Seismic Unix script PlotChirp created variable density postscript plots of the seismic profiles showing two-way travel time (seconds) along the y-axis (left margin) and shots along profile (labeled at 500 shot intervals) on the x-axis (along top of profile). The postscript images were converted to 150 dpi portable network graphic (PNG) images using ImageMagick (version 6.9.11-60). The plots are labeled along the bottom of the X axis. Data sources produced in this process:
    • PNG profile plots.
  3. What similar or related data should the user be aware of?
    Norris, M.W., and Faichney, A.K., 2002, SEG-Y rev. 1 Data Exchange Format - SEG Technical Standards Committee: Society of Exploration Geophysicists, Tulsa, OK.

    Online Links:

    Andrews, Brian D., Baldwin, Wayne E., Worley, Charles R., Moore, Eric M., Nichols, Alex R., Danforth, William W., Foster, David S., Ackerman, Seth D., and Brothers, Laura L., 2023, High-resolution geophysical data collected in Nantucket Sound Massachusetts in the vicinity of Horseshoe Shoal, during USGS Field Activity 2022-001-FA: data release DOI:10.5066/P9O5G5OT, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    This previous data release was also published as part of the USGS/CZM cooperative and may be of interest to others because it is directly south of, and overlaps, with the data collected during USGS Field Activity 2023-001-FA.
    Baldwin, W.E., Foster, D.S., Barnhardt., W.A., Schwab, W.C., Andrews, B.D., and Ackerman, S.D., 2016, Shallow Geology, Sea-floor Texture, and Physiographic Zones of Vineyard and western Nantucket Sounds, Massachusetts: Open-File Report 2016-1119, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Pendleton, E.A., Andrews, B.D., Ackerman, S.D., Danforth, W.W., and Foster, D.S., 2014, High-resolution geophysical data collected aboard the U.S. Geological Survey research vessel Rafael to supplement existing datasets from Buzzards Bay and Vineyard Sound, Massachusetts: Open-File Report 2013–1020, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Andrews, B.D., Ackerman, S.D., Baldwin, W.E., Foster, D.S., and Schwab, W.C., 2013, High-resolution geophysical data from the inner continental shelf at Vineyard Sound, Massachusetts: Open-File Report 2012–1006, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

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?
    The EdgeTech 3400 subbottom profiler was towed from the port side davit of the R/V Rafael. The towfish was suspended ~ 1 m below the water line from a catamaran float, and towed approximately 13 meters astern of the DGPS antenna mounted on the after end of the cabin while underway. Navigation data for the 3400 were collected using a Hemisphere DGPS receiver, and layback positioning of the towfish relative to the GPS antenna was calculated during processing. Positioning data were recorded using EdgeTech Discover Subbottom SBP (version 41.0.1.116) acquisition software, which logged coordinates to individual trace headers in JSF and SEG-Y format. During line 20230601_152830 the navigation feed to Discover was interrupted or provided spurious coordinates, in these instances position and time were derived from the Hypack raw files and merged with the traces during processing. DGPS horizontal positional accuracy is assumed to be within 3 m, but due to uncertainty associated with layback correction we assume a more conservative positional accuracy of within 13 m.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Sections of tracklines where navigation was recorded but no seismic data were logged are not included such as during testing, some turns, and very short files.
  5. How consistent are the relationships among the observations, including topology?
    Chirp seismic-reflection data were collected on the following dates: 20230601-20230602 (Julian day 152-153), 20220606-20220611 (Julian day 157-162). '2023-001-FA_ET3400_sht500.shp' contains the first, last, and 500-interval shotpoints for each seismic trackline, and '2023-001-FA_ET3400_shtnav.csv' contains all unique shot point navigation. The attribute fields 'LineName' and 'ImageName' for each polyline feature in '2023-001-FA_ET3400_Tracklines.shp' correspond to the SEG-Y data files in '2023-001-FA_ET3400_Segy.zip' and the PNG profile images in "2023-001-FA_ET3400_Images.zip", respectively. One SEG-Y file, and PNG image exists for each feature. Processed seismic data were converted to PNG format for ease of seismic trace display. Quality control was conducted during processing.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints. Please see 'Distribution Information' for details.
Use_Constraints These data are marked with a Creative Commons CC0 1.0 Universal License. These data are in the public domain and do not have any use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? USGS data release of EdgeTech 3400 chirp seismic-reflection data collected within Nantucket Sound Massachusetts in the vicinity of Horseshoe Shoal, during USGS Field Activity 2023-001-FA: includes '2023-001-FA_ET3400_sht500.shp' containing the first, last and 500-interval shotpoint locations, '2023-001-FA_ET3400_shtnav.csv' containing unique shot point locations, '2023-001-FA_ET3400_Tracklines.shp' containing trackline features, '2023-001-FA_ET3400_Images.zip' containing 98 PNG images named according to line convention, '2023-001-FA_ET3400_SegyData.zip' containing 98 SEG-Y files of the processed traces, the browse graphic 2023-001-FA_ET3400_browse.jpg, and Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (CSDGM) metadata file '2023-001-FA_ET3400_meta.xml'. These datasets can be downloaded individually (see the Digital Transfer Option section).
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    To utilize these data, the user must have software capable of reading shapefiles, CSV files, PNG images, and/or SEG-Y seismic trace files.

Who wrote the metadata?

Dates:
Last modified: 21-May-2026
Metadata author:
U.S. Geological Survey
Attn: Wayne Baldwin
Geologist
384 Woods Hole Rd.
Woods Hole, MA

(508) 548-8700 x2226 (voice)
(508) 457-2310 (FAX)
whsc_data_contact@usgs.gov
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is no longer with the USGS.
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P14NWTX8/2023-001-FA_ET3400_meta.faq.html>
Generated by mp version 2.9.51 on Tue May 26 15:03:12 2026