Backscatter intensity and sun-illuminated topographic imagery of the seafloor in the Stellwagen Bank National Marine Sanctuary region (bcksctter.tif)

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Frequently anticipated questions:

What does this data set describe?

Title:
Backscatter intensity and sun-illuminated topographic imagery of the seafloor in the Stellwagen Bank National Marine Sanctuary region (bcksctter.tif)
Abstract:
This data set contains the sun-illuminated topographic imagery and backscatter intensity generated from a multibeam sonar survey of the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts, an area of approximately 1100 square nautical miles. The Stellwagen Bank NMS Mapping Project is designed to provide detailed maps of the Stellwagen Bank region's environments and habitats and the first complete multibeam topographic and sea floor characterization maps of a significant region of the shallow EEZ.
Data were collected on four cruises over a two year period from the fall of 1994 to the fall of 1996. The surveys were conducted aboard the Canadian Hydrographic Service vessel Frederick G. Creed, a SWATH (Small Waterplane Twin Hull) ship that surveys at speeds of up to 16 knots. The multibeam data were collected utilizing a Simrad Subsea EM 1000 Multibeam Echo Sounder (95 kHz) that is permanently installed in the hull of the Creed.
Supplemental_Information:
For additional information about the field activities associated with this dataset, see https://cmgds.marine.usgs.gov/fan_info.php?fan=1994-008-FA, https://cmgds.marine.usgs.gov/fan_info.php?fan=1995-013-FA, https://cmgds.marine.usgs.gov/fan_info.php?fan=1996-032-FA, https://cmgds.marine.usgs.gov/fan_info.php?fan=1996-043-FA.
  1. How might this data set be cited?
    Valentine, Page C., Baker, Jessica L., and Unger, Tanya S., 2005, Backscatter intensity and sun-illuminated topographic imagery of the seafloor in the Stellwagen Bank National Marine Sanctuary region (bcksctter.tif): Scientific Investigations Map 2840, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Page C. Valentine (editor), 2005, Sea floor image maps showing topography, sun-illuminated topography, backscatter intensity, ruggedness, slope, and the distribution of boulder ridges and bedrock outcrops in the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts: Scientific Investigations Map 2840, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    1:60,000, 6 maps, 12 sheets. Suggested citation: Valentine, P.C., Baker, J.L., Unger, T.S., Sculy, L.A., Fuller, S.J., 2005, Sea floor image maps showing topography, sun-illuminated topography, backscatter intensity, ruggedness, slope, and the distribution of boulder ridges and bedrock outcrops in the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts: U.S. Geological Survey Scientific Investigations Map 2840, https://doi.org/10.3133/sim2840.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.600
    East_Bounding_Coordinate: -70.0333
    North_Bounding_Coordinate: 42.800
    South_Bounding_Coordinate: 42.0833
  3. What does it look like?
    http://pubs.usgs.gov/sim/2005/2840/data/backscatter/bcksctter-thumb.gif (GIF)
    Thumbnail image showing backscatter intensity and sun-illuminated topography of the seafloor in Stellwagen Bank National Marine Sanctuary region.
    http://pubs.usgs.gov/sim/2005/2840/data/backscatter/bcksctter-browse.gif (GIF)
    Browse image showing backscatter intensity and sun-illuminated topography of the seafloor in Stellwagen Bank National Marine Sanctuary region.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1994
    Ending_Date: 1998
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: remote-sensing image
  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 6199 x 3631 x 1, type Pixel
    2. What coordinate system is used to represent geographic features?
      The map projection used is Mercator.
      Projection parameters:
      Standard_Parallel: 41.650000
      Longitude_of_Central_Meridian: -70.316667
      False_Easting: 0
      False_Northing: 0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 13.000000
      Ordinates (y-coordinates) are specified to the nearest 13.000000
      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 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    Backscatter imagery combines the sun-illuminated topography with the backscatter intensity (shown here in color) of the sea floor. Backscatter intensity is a measure of the hardness and roughness of the sea floor as determined from the strength of sound waves reflected from the seabed during the survey. High-backscatter materials (red and orange) are coarse sand, gravel (including piles and ridges of boulders), and rock outcrops. Moderate backscatter (green) represents sand or muddy sand. Low backscatter (blue) represents sandy mud and mud. These interpretations apply best in region's of low regional topography, because steep slopes can divert the paths of some of the reflected sound waves away from the survey vessel. Thus, seabed that slopes steeply away from the survey track can produce a lower backscatter intensity than if it were level. Unnatural-looking stripes and patterns oriented parallel or perpendicular to survey track lines are artifacts of data collection. Blank areas represent places where no data exists.
    Entity_and_Attribute_Detail_Citation: Information unavailable from original metadata file.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Page C. Valentine
    • Jessica L. Baker
    • Tanya S. Unger
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Page C. Valentine
    U.S. Geological Survey
    Research Geologist
    U.S. Geological Survey
    Woods Hole, MA
    USA

    (508) 548-8700 x2239 (voice)
    (508) 457-2310 (FAX)
    pvalentine@usgs.gov

Why was the data set created?

Development of interpretive seabed maps, sea floor imagery, and a GIS database that are accessible to scientists, policymakers, managers, and the general public.

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: unknown (process 1 of 2)
    Multibeam data were processed using SwathEd, a suite of multibeam software editing and display tools developed by Dr. John Hughes Clarke of the Ocean Mapping Group, University of New Brunswick (UNB).
    Date: 08-Sep-2021 (process 2 of 2)
    The metadata was edited to remove errors as well as update some information. Edits include modifying the title to move the dataset name to the end of the title, adding the DOI link in the identification section, added the suggested citation, added supplemental information with link to the related field activity pages on CMGDS, added the USGS Thesaurus keywords, added keywords section with USGS persistent identifier as theme keyword, added online links to cross-references, replaced distribution liability with FSP statement, used a generic email address in metadata. The metadata date (20050822), but not the contact (except email and contact instructions) was updated. The metadata available from a harvester may supersede metadata available from the publication. Compare the metadata dates to determine which metadata file is most recent. Original edits on 20210816. An additional author name fix on 20210908. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?
    Valentine, Page C., Middleton, Tammie J., and Fuller, Sarah J., 2001, Sea floor maps showing topography, sun-illuminated topography, and backscatter intensity of the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts: Open-File Report 2000-410, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    Valentine, Page C., Baker, Jessica L., and Unger, Tanya S., 2003, Backscatter intensity and sun-illuminated sea Floor topography of the Stellwagen Bank National Marine Sanctuary off Boston, Massachusetts: Geologic Investigations Map I-2676-C, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole 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?
    The ship's position was determined with an accuracy of 10 m or better using a Magnavox 4200 geographic positioning system (GPS) receiver in conjunction with differential GPS corrections transmitted by U.S. Coast Guard radio beacons. At the start of each day, casts were made to record the sound velocity profile of the water column in the area to be surveyed. This information is used by the data acquisition system to correct for the refraction of the transmitted multibeam sound signal as it travels through the water to and from the sea floor.
  2. How accurate are the geographic locations?
    Sounding rates depend on water depth but vary from 2 to 4 per second in water depths less than 100 meters. Horizontal spatial resolution at these sounding rates is on the order of 10% of the water depth at 16 knots; however, vertical resolution is approximately 1% or better in the same depth range.
  3. How accurate are the heights or depths?
    Sounding rates depend on water depth but vary from 2 to 4 per second in water depths less than 100 meters. Horizontal spatial resolution at these sounding rates is on the order of 10% of the water depth at 16 knots; however, vertical resolution is approximately 1% or better in the same depth range.
  4. Where are the gaps in the data? What is missing?
    The sidescan-sonar backscatter data are displayed in real time on the Sun workstation using software designed and written by the Ocean Mapping Group, University of New Brunswick. This display allows data gaps to be identified during the survey and also gives a measure of the data quality.
  5. How consistent are the relationships among the observations, including topology?
    Multibeam echo sounder data was collected aboard the Canadian Hydrographic Service vessel Frederick G. Creed, an aluminum SWATH (Small Waterplane Area Twin Hull) ship that surveys at speeds up to 16 knots. The ship has two submerged torpedo-shaped hulls that support the main deck via two thin struts. This design reduces wave motion on the ship and resistance to the ship's forward motion through the water, thus making it a very stable platform at high survey speeds. Stability of the ship is also enhanced by the computer-controlled action of four stabilizer fins located fore and aft on the inboard side of the hulls. The stabilizers control the pitch and roll of the vessel and allow adjustment of the heel and trim of the ship while under way.
    An Applied Analytics POS/MV motion sensor located in the hull near the EM 1000 transducer detects changes in pitch, roll, and heave of the vessel. The motion information is recorded concurrently with the acquired multibeam signal and both are logged in a single file on the Sun workstation and made available to other workstations for further processing.

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 (USGS) as the source of this information.
  1. Who distributes the data set? (Distributor 1 of 1)
    Page C. Valentine
    U.S. Geological Survey
    Research Geologist
    U.S. Geological Survey
    Woods Hole, MA
    USA

    (508) 548-8700 x2239 (voice)
    (508) 457-2310 (FAX)
    pvalentine@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?
    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.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: A zip archive containing the GeoTIFF image, associated world file, and metadata. in format TIFF (version Information unavailable from original metadata file.) GeoTIFF
      Network links: http://pubs.usgs.gov/sim/2005/2840/data/backscatter/bcksctter.zip
      Media you can order: DVD-ROM (Density 4.75 Gbytes) (format UDF)
    • Cost to order the data: None

  5. What hardware or software do I need in order to use the data set?
    This image is available as a GEOTIFF image with an accompanying world file. To utilize this data, the user must have an image viewer, image processing or GIS software package capable of importing a GeoTIFF image.

Who wrote the metadata?

Dates:
Last modified: 08-Sep-2021
Metadata author:
U.S. Geological Survey
Attn: Page C. Valentine
Research Geologist
U.S. Geological Survey
Woods Hole, MA
USA

(508) 548-8700 x2239 (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 contact person is no longer with the USGS.
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/sim/sim2840/bcksctter-metadata.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:20:42 2021