USGS ASCII trackline bathymetry

Metadata also available as - [Outline] - [Parseable text]

Frequently-anticipated questions:

What does this data set describe?
    Title: USGS ASCII trackline bathymetry
    Abstract:
    These data represent single beam echo sounder (trackline) bathymetry collected in May 1995, May 1996, September 1996, May 1997, and October 1998 during five USGS cruises within the New York Bight region. Trackline spacing during these cruises was 300 meters. These data have been corrected for tidal fluctuations and distance of the transducer below the water line. All values are stored in meters. These data are referenced to Mean Lower Low Water.

  1. How should this data set be cited?

    Denny, Jane F. , 2000, USGS ASCII trackline bathymetry: U.S. Geological Survey, Woods Hole, MA.

    Online Links:

    • http:/woodshole.er.usgs.gov/project-pages/newyork

    This is part of the following larger work.

    Schwab, William C., Denny, Jane F., Foster, David S., Lotto, Linda L., Allison, Mead A., Uchupi, Elazar, Swift, B. Ann, Danforth, William W., Thieler, Robert E., and Butman, Bradford, 2002, High-Resolution Quaternary seismic stratigraphy of the New York Bight Continental Shelf: Open-File Report OFR02-152, U.S. Geological Survey, Woods Hole, MA.

     

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -74.13288
    East_Bounding_Coordinate: -71.71902
    North_Bounding_Coordinate: 41.15827
    South_Bounding_Coordinate: 40.08264

  3. What does it look like?

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

    Beginning_Date: 01-May-1995
    Ending_Date: 01-Nov-1998
    Currentness_Reference: ground condition

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

    Geospatial_Data_Presentation_Form: Raster Grid

  6. How does the data set represent geographic features?

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

      This is a raster data set. It contains the following raster data types:

      • Dimensions 382 x 690, type grid cell

    2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 18
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: .9996
      Longitude_of_Central_Meridian: -075.000000
      Latitude_of_Projection_Origin: +00.000000
      False_Easting: 500000
      False_Northing: 0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 5
      Ordinates (y-coordinates) are specified to the nearest 5
      Planar coordinates are specified in Meters

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298257.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: Mean Lower Low Water
      Altitude_Resolution: 1
      Altitude_Distance_Units: Meters
      Altitude_Encoding_Method: implicit coordinate
      Depth_System_Definition:
      Depth_Datum_Name: Local surface
      Depth_Resolution: 1
      Depth_Distance_Units: Meters
      Depth_Encoding_Method: Attribute values

  7. How does the data set describe geographic features?

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?

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

Why was the data set created?
Beginning in 1995, the USGS, in cooperation with the U.S Army Corps of Engineers (USACE), New York District, began a program to generate reconnaissance maps of the sea floor offshore of the New York-New Jersey metropolitan area, one of the most populated coastal regions of the United States. The goal of this mapping program is to provide a regional synthesis of the sea-floor environment, including a description of sedimentary environments, sediment texture, seafloor morphology, and geologic history to aid in understanding the impacts of anthropogenic activities, such as ocean dumping. This mapping effort differs from previous studies of this area by obtaining digital, sidescan-sonar images that cover 100 percent of the sea floor. This investigation was motivated by the need to develop an environmentally acceptable solution for the disposal of dredged material from the New York- New Jersey Port, by the need to identify potential sources of sand for nourishment of the southern shore of Long island, and by the opportunity to develop a better understanding of the transport and long-term fate of contaminants by investigations of the present distribution of materials discharged into the New York Bight over the last 100+ years (Schwab and others, 1997).

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: 2000 (process 1 of 4)
    Bathymetric data were extracted from the survey navigation and stored as an ASCII file, listing longitude, latitude, and depth in meters. These data were then reformatted and loaded into MATLAB (MathWorks, Inc.). The trackline spacing during data acquisition was 300 meters.

    Person who carried out this activity:

    Jane Denny
    U. S. Geological Survey
    Seafloor Mapping Group
    384 Woods Hole Rd
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

    Date: 2000 (process 2 of 4)
    Within MATLAB (MathWorks, Inc), a median filter with a 15 pixel boxcar size was applied to the bathymetric data to remove spurious spikes and anomolous readings. In order to account for the distance of the transducer below the sea surface, one meter was added to the bathymetric values. These data were then corrected for tidal fluctuations. The ADCIRC circulation model was used to extract tidal coefficients at the locations along the cruise track. A low-pass filter was applied to the Sandy Hook, NJ and Montauk Point, NY tidal stations to determine the wind compenent to the tides within the New York Bight region. A weighted distance interpolation was used between the two tidal stations in order to determine the tidal wind component along the cruise track. Final bathymetric values were determined by subtracting the wind component and tidal offset from the original bathymetric measurement. These values were then exported from Matlab and reformatted to load into EarthVision (Dynamic Graphics, Inc.)

    Person who carried out this activity:

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

    Data sources used in this process:

    Date: 2000 (process 3 of 4)
    The tidally corrected bathymetric soundings were loaded into EarthVision (Dynamic Graphics, Inc.). These point data were gridded at a 300 meter grid cell size, yielding a grid size of 214 rows x 488 columns. (The 300 meter grid cell size was chosen based on the trackline spacing during data acquisition (300m)).The point data were further editted to remove anomolous points by contouring the bathymetric grid, and using the contour and grid information to locate anomolous soundings. The grid was exported from EarthVision as an ASCII Raster file and edited to create a file suitable for import to ArcView software. The order of rows were flipped, so that the file begins with the lower row, left column and ends with the upper row right column. An ArcView header that descibes the lower left origin of the grid, the grid cell size, the number of rows and columns, and the null value used (-9999). Contour data were also exported from within EarthVision, and reformatted for import into ArcView software as an ESRI generate file.

    Person who carried out this activity:

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

    Date: 2002 (process 4 of 4)

    The original bathymetric grid extended beyond the bounds of the 1995 and 1996 study areas; the data covered offshore areas from New York - New Jersey to southern shore of Long Isand. A GRIDCLIP script was used in ArcView 3.2 to clip the original bathymetric grid to the bounds of the 1995 and 1996 surveys.

    Person who carried out this activity:

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

  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?

    These data are internally consistent and have been compared to multibeam and single-beam bathymetric surveys to check for accuracy. Any differences between this bathymetric data set and others were determined to be within acceptable error given the inherent differences in the various bathymetric data sets (i.e. acquisition system, mode of navigation, density of point, and or swath bathymetry).

  2. How accurate are the geographic locations?

    DGPS is assumed to be accurate within 1-2 meters. Standard GPS is assumed accurate within 5-10 meters. 99% of the positional data is DGPS. Unless noted, all GPS/DGPS data is referenced to WGS84 (NAD83). The configuration of the fathometer is as follows: The fathometer is mounted on either the port or starboard side of the vessel. Offset between the sidemount and GPS antennae is measured. No measurements were taken of ship's pitch, yaw, heave, or change in draft due to water and fuel usage. Motion of the fathometer is not measured. Horizontal accuarcy of the fathometer is assumed to be within +/- 3 meters.

  3. How accurate are the heights or depths?

    A one meter offset was measured from the water line to the tranducer. This offset was added to the bathymetric measurements. Tidal fluctuations have also been accounted for within these data. No motion sensor monitors the movement of the fathometer or vessel (pitch, heave, yaw). As such, the working vertical accuracy of these data is +/- 0.5 - 1 meter. These data are referenced to Mean Lower Low Water.

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

    Complete

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

    These data are were checked for consistency by plotting the point data with the contoured surface and eliminating suprious and anomolous soundings.

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:
These data are not to be used for navigational purposes.

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

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

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

    b_of_grd

  3. What legal disclaimers am I supposed to read?

    Altough this data set and its lineage have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or it's related materials. 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 items. Users must assume responsibility for the proper use of this data. This data should not be used at resolutions for which it is not intended. This data has no been reviewed for conformity with US Geological Survey editorial standards, or the North American Strigraphic code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the US Government.

  4. How can I download or order the data?

Who wrote the metadata?
Dates:
Last modified: 19-Jan-2002
Last Reviewed: 2002

Metadata author:
Jane F. Denny
US Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, MA 02543
USA

508-457-2311 (voice)
508-457-2310 (FAX)
jdenny@usgs.gov

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

Generated by mp version 2.7.17 on Thu Apr 11 12:21:34 2002