Sea floor topography and backscatter intensity of the Hudson Shelf Valley Region.

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Frequently anticipated questions:

What does this data set describe?

Sea floor topography and backscatter intensity of the Hudson Shelf Valley Region.
This data set includes topography and backscatter intensity of the sea floor of the Hudson Shelf Valley, located offshore of New York and New Jersey. The data were collected with a multibeam sea floor mapping system on surveys conducted November 23 - December 3, 1996, October 26 - November 11, 1998, and April 6 - 30, 2000. The surveys were conducted using a Simrad EM 1000 multibeam echo sounder mounted aboard the Canadian Hydrographic Service vessel Frederick G. Creed. This multibeam system utilizes 60 electronically aimed receive beams spaced at intervals of 2.5 degrees that insonify a strip of sea floor up to 7.5 times the water depth (swath width of 100 to 200 m within the survey area). Maps derived from the mulitbeam observations show sea floor topography, shaded relief, and backscatter intensity (a measure of sea floor texture and roughness). The data are gridded at 12 m/pixel. THIS DATA SET IS PRELIMINARY; PUBLICATION OF A FINAL DATA SET IS PLANNED IN 2003
  1. How might this data set be cited?
    U.S. Geological Survey, 2003, Sea floor topography and backscatter intensity of the Hudson Shelf Valley Region.: U.S. Geological Survey Open-File Report 01-470, U.S. Geological Survey, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Butman, Bradford, Gutierrez, Benjamin T., ten Brink, Marilyn Buchholtz, Schwab, William C., Blackwood, Dann S., Mecray, Ellen L., and Middleton, Tammie J., 2003, Photographs of the sea floor offshore of New York and New Jersey: U.S. Geological Survey Open-File Report 01-470, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -73.901667
    East_Bounding_Coordinate: -72.166667
    North_Bounding_Coordinate: 40.433333
    South_Bounding_Coordinate: 39.4333333
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1996
    Ending_Date: 2000
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: remote-sensing image 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 Raster data set. It contains the following raster data types:
      • Dimensions 5074 x 6165, type Pixel
    2. What coordinate system is used to represent geographic features?
      The map projection used is Mercator.
      Projection parameters:
      Standard_Parallel: 40.0
      Longitude_of_Central_Meridian: -75
      False_Easting: 0
      False_Northing: 0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 12
      Ordinates (y-coordinates) are specified to the nearest 12
      Planar coordinates are specified in meters
      The ellipsoid used is World Geodetic System 84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257.
      Depth_Datum_Name: Mean sea level
      Depth_Resolution: 0.3
      Depth_Distance_Units: Meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates
  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)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
    Multibeam data collected by the U.S. Geological Survey, Bradford Butman principal investigator. Parts of the data presented here are published in Butman and others (1998) (USGS Open-File Report 98-616; online at and Butman and others (2002) (USGS Open-File Report 00-503; online at Publication of a final data set planned for 2003.
  3. To whom should users address questions about the data?
    U. S. Geological Survey
    Attn: Bradford Butman
    384 Woods Hole Rd
    Woods Hole, MA

    508-457-2212 (voice)
    508-457-2309 (FAX)

Why was the data set created?

These preliminary data are included in this publication to provide bathymetry and backscatter intensity for maps showing the locations of images and samples obtained in the New York Bight. THIS DATA SET IS PRELIMINARY; PUBLICATION OF A FINAL DATA SET IS PLANNED IN 2003.

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: 1996 (process 1 of 2)
    (1) Data and acquisition processing at sea After the echo sounder data were logged onto the hard disk of the Sun workstation, a suite of processing software developed by the Ocean Mapping Group ( was used to correct for artifacts and errors that may have been introduced during data collection. This software also enhanced the corrected data by resolving beam pattern and aspect ratio distortions and by imposing a linear contrast stretch before it generated bathymetric and sidescan sonar image mosaicks in a Mercator projection. All data processing described here is initiated using Silicon Graphics workstations as soon as each acquisition file is closed by the Simrad Mermaid workstation (usually at the end of each survey line). Additional processing was done in the lab to correct for fluctuations in sea level during the survey and for artifacts in the data files that were not corrected in the field (see below).
    The processing and editing steps on board the ship were:
    (A.) Demultiplex, or unravel, the acquired Simrad data files using RT to generate separate files containing navigation, depth soundings, sidescan sonar backscatter values, and sound velocity information.
    (B.) Automatically reject bad data (autoRejectSoundings). For the multibeam soundings, reject data outside expected depth ranges (operator's decision based on nautical chart data); for navigation data, reject fixes with poor GPS statistics.
    (C.) Edit the navigation data on-screen using jview to remove undesirable points, including turns at the ends of survey lines.
    (D.) Edit the multibeam soundings on-screen using swathed to remove individual anomalous soundings.
    (F.) Map the bathymetric soundings from each processed data file onto a Mercator grid using weigh_grid with node spacings and scale selected by the operator.
    (G.) Map the extracted sidescan sonar backscatter values onto a digital mosaic using mos2 in the Mercator projection at a scale selected by the user.
    (H.) Using addSUN, generate bathymetric raster files using the mapped grid node information to depict the depth information in a shaded relief Mercator map. A Mercator projection allows individual map areas to be joined edge to edge when creating a composite image. The shaded relief images were generated using a sun elevation angle of 45 degrees from an azimuth of 0 degrees, and a vertical exaggeration of four times to emphasize sea floor features.
    (I.) Generate a false colored image using mix_ci by combining the bathymetric and backscatter raster mosaics into a single image, also in the Mercator projection.
    Additional processing in the laboratory included adjusting the bathymetric observations to mean sea level using predictions of the ADCIRC tidal model (see Westerink, J.J., R.A. Luettich, Jr. and J. Muccino, 1994, "Modeling Tides in the Western North Atlantic Using Unstructured Graded Grids", Tellus, 46a(2):178-199.)

    All mapped files are in the Mercator projection, having a central longitude of -75 degrees West, a latitude of true scale of 40 degrees north and the horizontal datum is WGS84. The vertical datum is mean sea level, referenced to the ADCIRC model.
    Person who carried out this activity:
    William Danforth
    U.S. Geological Survey
    Operational Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2274 (voice)
    508-457-2310 (FAX)
    Date: 16-Dec-2002 (process 2 of 2)
    Creation of original metadata record Person who carried out this activity:
    Brad Butman
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA

    508.548.8700x2212 (voice)
  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?
    These data were navigated with a Differential Global Positioning System (DGPS); they are accurate to +/- 3 meters, horizontally.
  3. How accurate are the heights or depths?
    These data have been corrected for vessel motion (roll, pitch, heave, yaw). They have been corrected for tidal offsets using the sea level predicted using the ADCIRC tidal model. Additional corrections will be made. The vertical resolution of the Simrad EM-1000 multibeam echosounder is about 1 % of water depth.
  4. Where are the gaps in the data? What is missing?
    These data are prelimary. Additional processing will be carried out to correct to mean low water, and to correct projection issues.
  5. How consistent are the relationships among the observations, including topology?

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: This information is not for navigational purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    Bradford Butman
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, Massachusetts

    508-548-2212 (voice)
    508-457-2309 (FAX)
  2. What's the catalog number I need to order this data set?
  3. What legal disclaimers am I supposed to read?
    These data were prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Although all data 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 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 materials.
  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 04-Feb-2015
Last Reviewed: 22-Jul-2004
Metadata author:
Peter N Schweitzer
USGS Midwest Area
Collection manager, USGS Geoscience Data Clearinghouse,
Mail Stop 954
12201 Sunrise Valley Dr
Reston, VA

703-648-6533 (voice)
703-648-6252 (FAX)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

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