U.S. Geological Survey, 2010, DH_SeismicTrackline: Survey lines along which EdgeTech SB-512i and SB-424 chirp seismic-reflection data were collected by the U.S. Geological Survey offshore of Massachusetts between Duxbury and Hull.: Open-File Report 2009-1072, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, Massachusetts.This is part of the following larger work.Online Links:
- <https://pubs.usgs.gov/of/2009/1072/GIS/shapefile/DH_SeismicTrackline.zip>
- <https://pubs.usgs.gov/of/2009/1072/html/appendix1.html>
Barnhardt, Walter A. , Ackerman, Seth D. , Andrews, Brian D. , and Baldwin, Wayne E. , 2010, Geophysical and Sampling Data from the Inner Continental Shelf: Duxbury to Hull, Massachusetts.: Open-File Report 2009-1072, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, Massachusetts.Online Links:
This is a Vector data set. It contains the following vector data types (SDTS terminology):
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.
Sequential unique whole numbers that are automatically generated
Coordinates defining the features
Character string of width 50
Character string of width 254
Character string of width 254
Character string of width 254
| Range of values | |
|---|---|
| Minimum: | 0.565872 |
| Maximum: | 14.599348 |
Character string of width 10
Character string of width 15
Character string of width 25
508-548-8700 x2226 (voice)
508-457-2310 (FAX)
wbaldwin@usgs.gov
This dataset contains trackline navigation for approximately 1920 km of EdgeTech SB-512i and SB-424 chirp seismic-reflection data collected by the U.S. Geological Survey during two Woods Hole Science Center cruises (06012 and 07001) offshore of Massachusetts between Duxbury and Hull.
Seismic-reflection data acquisition 07001: Chirp seismic data were collected using an EdgeTech Geo-Star FSSB sub-bottom profiling system and an SB-424 towfish (4-24 kHz), which was mounted on a rigid pole on the starboard side of the R/V Rafael of Woods Hole, MA. EdgeTech J-Star and Triton Imaging Inc. SB-Logger seismic acquisition software was used to control the Geo-Star topside unit and digitally log trace data in EdgeTech JSF and SEG-Y Rev. 1 formats, respectively. Data were acquired using a 0.25-s shot rate, a 10-ms pulse length, and a 4 to 16 kHz frequency sweep. Recorded trace lengths were approximately 250 ms. Tracklines were spaced 100 m apart in the shore parallel direction and between 200 m and 2 km apart in the shore perpendicular direction.
Person who carried out this activity:
508-548-8700 x2226 (voice)
508-457-2310 (FAX)
wbaldwin@usgs.gov
Person who carried out this activity:
508-548-8700 x2226 (voice)
508-457-2310 (FAX)
wbaldwin@usgs.gov
During the initial loop through the script: 1) Easting and northing coordinates (UTM Zone 19, WGS84) for the first five traces of input navigation were read and easting and northing differentials between the consecutive positions were calculated; 2) The signs (+/-) of the differential values were compared to a look-up table to determine the appropriate conversion of the arc tangent (atan2(dy,dx)) angle between consecutive positions to a polar azimuth; 3) The average of the polar azimuths was calculated; 4) The sine and cosine of the average azimuth was calculated and multiplied by the linear distance between the catamaran and the shipboard RTK-GPS receiver, providing absolute values for easting and northing offsets, respectively; 5) A look-up table was used to determine the quadrant of the average azimuth and appropriately add or subtract the calculated offsets to the easting and northing coordinates of the first three input traces, producing final layback positions for those traces; 6) Layback and original easting and northing coordinates for the three adjusted traces were printed to a new layback navigation file that also retained additional attributes input records; and 7) Easting and northing coordinates of the fourth and fifth traces, the three azimuths computed between traces two, three, four, and five, and the average azimuth were held as input for calculations conducted in the subsequent loop.
During subsequent loops through the script: 1) Easting and northing coordinates for three additional traces from input navigation were read, and easting and northing differentials were calculated between the consecutive positions, including the last trace position held from the previous loop; 2) Three new polar azimuths were calculated using the differential values, then a new average azimuth was calculated from the three that were held, the new three, and the average held from the previous loop (the previously calculated average was factored into the new average to smooth "kinks" along the layback navigation that can result from significantly different average azimuths calculated from one loop to the next); 3) New layback offset values were computed, and applied to the easting and northing coordinates of the last two traces input during the previous loop, and the fist trace input during the present loop. 4) Layback and original easting and northing coordinates for the three adjusted traces were appended to the layback navigation file started in the previous loop; and 5) Easting and northing coordinates of the second and third traces, the three new azimuths, and the average azimuth from the present loop were held as input for calculations conducted in the subsequent loop.
Near the end of the input navigation file: 1) If less than three traces were present during a new loop, the layback offsets calculated during the previous loop were applied to remaining trace coordinates; 2) Layback and original easting and northing coordinates for the remaining adjusted traces were appended to the layback navigation file; and 3) The script reached its end, closed, and saved the layback navigation file.
In this fashion, the script approximated a moving window, in which the average of six trace to trace azimuths was used to calculate layback offsets for three central trace positions. Exceptions were at the start of a file, where the first three input trace positions were adjusted using offsets calculated from the average of only four azimuths, and possibly at the end of a file, where remaining traces may have been adjusted using the offsets calculated during the previous loop.
Person who carried out this activity:
508-548-8700 x2226 (voice)
508-457-2310 (FAX)
wbaldwin@usgs.gov
Person who carried out this activity:
508-548-8700 x2226 (voice)
508-457-2310 (FAX)
wbaldwin@usgs.gov
Person who carried out this activity:
508-548-8700 x2226 (voice)
508-457-2310 (FAX)
wbaldwin@usgs.gov
Stockwell, John, 2008, CWP/SU: Seismic Uni*x: Center for Wave Phenomena - Colorado School of Mines, Golden, CO.Online Links:
Henkart, Paul, 2007, SIOSEIS: Scripps Institution of Oceanography, University of California - San Diego, LaJolla, CA.Online Links:
Michael W. Norris and Alan K. Faichney, 2002, SEGY Rev.1 Data Exchange Format1: Society of Exploration Geophysicists, Tulsa, OK.Online Links:
Barnhardt, Walter A. , Andrews, Brian D. , and Butman, Bradford, 2006, High-Resolution Mapping of the Inner Continental Shelf: Nahant to Gloucester, Massachusetts: Open-File Report 2005-1293, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.Online Links:
Ackerman, Seth D. , Butman, Bradford, Barnhardt, Walter A. , Danforth, William W. , and Crocker, James M. , 2006, High-Resolution Geologic Mapping of the Inner Continental Shelf: Boston Harbor and Approaches, Massachusetts: Open-File Report 2006-1008, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.Online Links:
Barnhardt, Walter A. , Andrews, Brian D. , Ackerman, Seth D. , Baldwin, Wayne E. , and Hein, Christopher J. , 2009, High-Resolution Geological Mapping of the Inner Continental Shelf: Cape Ann to Salisbury Beach, Massachusetts: Open-File Report 2007-1373, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.Online Links:
All attributes were checked in a consistent manner.
Field activity 06012: The SB-0512i was mounted on a catamaran sled and towed at the sea surface approximately 30 - 40 m astern of the R/V Megan T. Miller. Position data were provided by a Global Positioning System (GPS) navigation receiver mounted on the catamaran, and data were transmitted to the acquisition computer on the vessel via a 2.4 GHz radio link. During some portions of the survey, technical difficulties caused the GPS system mounted on the catamaran to malfunction. In these instances Real Time Kinematic (RTK) GPS navigation was obtained from a receiver mounted above the interferometric sonar head (This applies to files l25f2000 through l84f2000 acquired during Julian days 218 through 222). Layback positions, which account for the linear distance between the shipboard RTK-GPS receiver and the towed catamaran vehicle, were calculated trigonometrically during post-processing (see processing step 3). While the vehicle mounted GPS antenna was operational, positional accuracy is assumed to be ± 10 m. While the vehicle mounted GPS was not operational, positional accuracy is assumed to be ± 20 m; increased uncertainty arises because layback calculations do not account for fish motion behind the vessel, which is caused by sea state and vessel speed induced changes in the angle and scope of the tow cable.
Field activity 07001: The SB-424 was mounted on a rigid pole, approximately 1 m below the sea surface on the starboard side of the R/V Rafael. Position data were provided by a RTK-GPS navigation receiver mounted directly above the interferometric sonar head. While horizontal offsets between the SB-424 transducer and the RTK-GPS navigation receiver were not corrected in the sonar setup, this distance was less than 3 m, and the resulting positional accuracy is assumed to be ± 10 m.
Sections of tracklines where navigation was recorded but no seismic data were logged are not included. Only the subsets of seismic-reflection data collected during field activities 06012 and 07001 that are within the study area between Duxbury and Hull have been included in this spatial dataset. Trackline navigation for approximately 945 km of additional seismic-reflection profiles collected south of Brant Rock, Massachusetts during these field activities will be published in a subsequent data release focused on Cape Cod Bay.
Any spurious data points were removed during processing. For each seismic trackline there is one seismic-profile image that is hyperlinked by the field 'IMAGENAME'. No duplicates exist.
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.
508-548-8700 x2226 (voice)
wbaldwin@usgs.gov
Downloadable Data
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.
| Data format: | Trackline navigation for EdgeTech SB-512i and SB-424 chirp seismic-reflection data collected by the U.S. Geological Survey offshore of Massachusetts between Duxbury and Hull in format SHP (version ArcGIS 9.2) ESRI polyline shapefile Size: 4.4 Mb |
|---|---|
| Network links: |
<https://pubs.usgs.gov/of/2009/1072/GIS/shapefile/DH_SeismicTrackline.zip> |
| Media you can order: |
DVD-ROM
(Density 4.75
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This zip file contains data available in Environmental Systems Research Institute (ESRI) point shapefile format. The user must have ArcGIS or ArcView 3.0 or greater software to read and process the data file. 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.
508-548-8700 x2226 (voice)
508-457-2310 (FAX)
wbaldwin@usgs.gov
