NC_tracklines.shp: Trackline navigation for EdgeTech SB-512i chirp seismic-reflection data collected in May 2012 by the U.S. Geological Survey within the Norfolk Canyon, mid-Atlantic margin (Esri polyline shapefile, Geographic, WGS 84)

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Frequently-anticipated questions:

What does this data set describe?

Title:
NC_tracklines.shp: Trackline navigation for EdgeTech SB-512i chirp seismic-reflection data collected in May 2012 by the U.S. Geological Survey within the Norfolk Canyon, mid-Atlantic margin (Esri polyline shapefile, Geographic, WGS 84)
Abstract:
A large number of high-resolution geophysical surveys between Cape Hatteras and Georges Bank have been conducted by federal, state, and academic institutions since the turn of the century. A major goal of these surveys is providing a continuous view of bathymetry and shallow stratigraphy at the shelf edge in order to assess levels of geological activity during the current sea level highstand. In 2012, chirp seismic-reflection data was collected by the U.S. Geologial Survey aboard the motor vessel Tiki XIV near three United States mid-Atlantic margin submarine canyons. These data can be used to further our understanding of passive continental margin processes during the Holocene, as well as providing valuable information regarding potential submarine geohazards. For more information on the U.S. Geological Survey involvement in this effort, see <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2012-005-FA>.
  1. How should this data set be cited?

    U.S. Geological Survey, 2014, NC_tracklines.shp: Trackline navigation for EdgeTech SB-512i chirp seismic-reflection data collected in May 2012 by the U.S. Geological Survey within the Norfolk Canyon, mid-Atlantic margin (Esri polyline shapefile, Geographic, WGS 84): Open-File Report 2014-1118, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts.

    Online Links:

    This is part of the following larger work.

    Obelcz, Jeffrey, Brothers, Daniel S. , Uri S. ten Brink, Chaytor, Jason D. , Worley, Charles R. , and Moore, Eric M. , 2014, Chirp Seismic-Reflection Data From the Baltimore, Washington, and Norfolk Canyons, U.S. Mid-Atlantic Margin: Open-File Report 2014-1118, U.S. Geological Survey, Reston, Virginia.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -74.818539
    East_Bounding_Coordinate: -74.530725
    North_Bounding_Coordinate: 37.193447
    South_Bounding_Coordinate: 37.003275

  3. What does it look like?

    <https://pubs.usgs.gov/of/2014/1118/Norfolk_Canyon/GIS/NC_tracklines_browse.jpg> (JPEG)
    EdgeTech 512i trackline navigation within and around Norfolk Canyon

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 25-May-2012
    Beginning_Time: 0937 (UTC)
    Ending_Date: 27-May-2012
    Ending_Time: 0715 (UTC)
    Currentness_Reference: ground condition of survey on dates 20120525-20120527

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • String (89)

    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 D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.

  7. How does the data set describe geographic features?

    NC_tracklines
    trackline for seismic profiles (Source: USGS)

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    Id
    attribute automatically generated by the software that converts points to lines (Source: software)

    Range of values
    Minimum:0
    Maximum:0
    Units:unitless

    line
    line name corresponding to PNG format seismic-reflection profile images. The format of the linename is a combination of the survey line and the processing of the SEG-Y data. The line number is in the format LXXFY where XX is the line number, and Y is the file number on that line (in case more than one file was used to acquire a line). Lines with "topmute_sf" indicate that the software SIOSEIS was used to mute the first 10 ms of each seismic trace and then used identify the seafloor and then use this information to process 'swell' to minimize the effect of sea surface heave. Lines with only "sf" in the name had to have the seafloor manually picked and then insert that information into the SEG-Y header to enable the sea surface heaving to be minimized. (Source: USGS)

    character set.

    lon
    longitude value of first shot of line (decimal degree, WGS84) (Source: USGS)

    Range of values
    Minimum:-74.818539
    Maximum:-74.532617
    Units:decimal degrees
    Resolution:0.000001

    lat
    latitude value of first shot of line (decimal degree, WGS84) (Source: USGS)

    Range of values
    Minimum:37.003856
    Maximum:37.193447
    Units:decimal degrees
    Resolution:0.000001

    year
    calendar year data were collected (Source: USGS)

    Range of values
    Minimum:2012
    Maximum:2012
    Units:year
    Resolution:1

    jd_hour_mi
    time of first shot of line (Julian Day:hour:minute:second). Julian day is the integer number representing the interval of time in days since January 1 of the year. (Source: USGS)

    Although the value is represented as a number, the number as a whole doesn't have a meaning. This value has to be broken down to its separate components (julian day, hour, minute, second) to have numerical significance.

    lon_end
    longitude value of last shot of line (decimal degree, WGS84) (Source: USGS)

    Range of values
    Minimum:-74.818094
    Maximum:-74.530725
    Units:decimal degrees
    Resolution:0.000001

    lat_end
    latitude value of last shot of line (decimal degree, WGS84) (Source: USGS)

    Range of values
    Minimum:37.004011
    Maximum:37.193042
    Units:decimal degrees
    Resolution:0.000001

    jd_hou_end
    time of last shot of line (Julian Day:hour:minute:second). Julian day is the integer number representing the interval of time in days since January 1 of the year. (Source: USGS)

    Although the value is represented as a number, the number as a whole doesn't have a meaning. This value has to be broken down to its separate components (julian day, hour, minute, second) to have numerical significance.

    hlink
    Relative path and filename that can be used to hotlink the trackline to the corresponding seismic-reflection profile image. (Source: U.S. Geological Survey)

    Character set.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    Jeffrey Obelcz
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    U.S.A.

    508-548-8700 x. 2245 (voice)
    508-457-2310 (FAX)
    jobelcz@usgs.gov

Why was the data set created?

This dataset contains trackline navigation for over 330 km of EdgeTech SB-512i Chirp seismic-reflection data collected by the U.S. Geological Survey during Woods Hole Coastal and Marine Science Center cruise 2012-005-FA within Norfolk Canyon. This dataset provides the GIS trackline navigation that corresponds readily with images produced from the seismic-reflection data. The dataset also serves as a navigation archive.

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, raw seismic navigation.

    Source_Contribution:
    Seismic-reflection data acquisition: Chirp seismic data were collected using an EdgeTech SB-0512i towfish (0.5-4.5 kHz pulse, 50 ms pulse length), which was towed astern of the M/V Tiki XIV of Ocean City, MD. Chesapeake Technologies' SonarWiz (v.4.04.0031) seismic acquisition software was used to control the chirp, digitally log trace data in the SEG-Y Rev. 1 format (IEEE floating point), and record GPS navigation coordinates to the SEG-Y trace headers (in arc seconds of Latitude and Longitude, multiplied by a scalar of 100). Trace lengths are constant within lines, but vary from line to line due to variable water depth in the survey area (the minimum trace length was 250 ms and the maximum 1400 ms). This yields a range of samples per trace from approximately 5435 (250 ms trace length) to 30435 (1400 ms trace length). Sample interval was kept at a constant .000046 s. The ping rate was set to be consistent with the trace length, so it varied between 250 ms and 1400 ms.

  2. How were the data generated, processed, and modified?

    Date: Jun-2012 (process 1 of 4)
    Seismic Unix (version 4.2) was used to read SEG-Y files, write a Seismic Unix file, and extract SEG-Y trace header information, including shot number, longitude, latitude, year, Julian day, and time of day (UTC). Header information from each SEG-Y file was saved to text files after an AWK (no version) filter was used to maintain shots at multiples of 100 and shots with unique navigation coordinates. End shots and shots at multiples of 100 may not have unique navigation coordinates. Separate text files containing unique shot navigation were also produced.

    Person who carried out this activity:

    Jeffrey Obelcz
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x. 2245 (voice)
    jobelcz@usgs.gov

    Date: May-2013 (process 2 of 4)
    The 100 shot interval text files produced from process step 1 were concatenated into a comma-delimited text file, then the text file was imported into ArcMap (version 9.3) using 'Add XY data' and saved as points (Geographic, WGS84) in the Esri shapefile format.

    Person who carried out this activity:

    Jeffrey Obelcz
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x. 2245 (voice)
    jobelcz@usgs.gov

    Date: May-2013 (process 3 of 4)
    The shapefile containing 100 shot interval positions, created in the previous step, was used as an input for VACExtras (version 3.1.2), a VB collection of tools developed by VeeAnn Cross (USGS-WHSC), which converts point data to a new polyline shapefile ('BC_tracklines.shp').. The 'line' field was used to define which points were used to generate each polyline feature, and the fields "lon " (line beginning longitude), "lat" (line beginning latitude), "jd_hour_mi" (line time start), "year" (year of data acquistion), "lon_end" (line ending longitude), "lat_end" (line ending latitude), and "jd_hou_end" (line ending time) were included as attributes in the output shapefile.

    Person who carried out this activity:

    Jeffrey Obelcz
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x. 2245 (voice)
    jobelcz@coastal.edu

    Date: Jan-2014 (process 4 of 4)
    The attribute "hlink" was added to the shapefile in ArcMap 9.3.1 and populated with the relative path and seismic-reflection profile image filename corresponding to the trackline. This allows the user to "hotlink" to the seismic profiles from within ArcMap. In order for this to work, the user must activate the "Hyperlinks" option of the dataset properties display tab. The field to use is "hlink" and the link type is a document. In the ArcMap - File - Document properties the user needs to supply the hyperlink base This is the remainder of the file location path prior to the data folder indicated in the "hlink" attribute.

    Person who carried out this activity:

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts 02543-1598
    USA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov

  3. What similar or related data should the user be aware of?

    Stockwell, John, 2011, CWP/SU: Seismic Uni*x: Center for Wave Phenomena - Colorado School of Mines, Golden, CO.

    Online Links:

    Henkart, Paul, 2011, SIOSEIS: Scripps Institution of Oceanography, UC San Diego, La Jolla, California.

    Online Links:

    Michael W. Norris and Alan K. Faichney, 2002, SEGY Rev. 1 Data Exchange Format 1: Society of Exploration Geophysicists, Tulsa, OK.

    Online Links:

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    All attributes were checked in a consistent manner.

  2. How accurate are the geographic locations?

    The SB-0512i was towed 3 meters below the sea surface approximately 10 m astern of the M/V Tiki XIV. Position data were provided by a Differential Global Positioning System (DGPS) navigation receiver mounted on the port aft side of the cabin. Layback positions, which account for the linear distance between the shipboard DGPS receiver and the towed chirp fish, were not calculated nor accounted for in the navigation. Positional accuracy is assumed to be +/- 20 m; layback calculations do not account for fish motions behind the vessel caused by sea state/ship speed changes in angle and scope of the tow cable.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Lines were serially recorded during the survey in the format "LXF1". When a file is named "LXF2" or has a file number greater than 2, the recording parameters were usually changed (record length and shot rate), as recorded in the ship's log. The following lines were either not recorded or excluded from this data release: L82F1, L87F1, L99F1, L115F1, L142F1 (all excluded due to negligible length).

  5. How consistent are the relationships among the observations, including topology?

    Any spurious data points were removed during processing. For each seismic trackline there is one seismic-profile image. No duplicates exist.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Use_Constraints:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the source of this information.

  1. Who distributes the data set? (Distributor 1 of 1)

    Jeffrey Obelcz
    U.S. Geological Survey, Woods Hole Science Center
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-548-8700 x. 2245 (voice)
    jobelcz@usgs.gov

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm 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?

    This zip file contains data available in Esri shapefile format. The zip file also contains associated metadata. The user must have software capable of uncompressing the zip file and displaying the shapefile. In lieu of ArcView or ArcGIS, the user may utilize another GIS application package capable of importing the data. A free data viewer, ArcExplorer, capable of displaying the data is available from Esri at www.esri.com.

Who wrote the metadata?

Dates:
Last modified: 23-Jun-2014
Metadata author:
Jeffrey Obelcz
U.S. Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, MA 02543-1598
USA

508-548-8700 x. 2245 (voice)
508-457-2310 (FAX)
jobelcz@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Generated by mp version 2.9.6 on Tue Jun 24 09:53:56 2014