GeoTIFF image of the backscatter intensity of the sea floor southwest of Montauk Point, New York, in 1998 (3-m resolution, Mercator, WGS 84)

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Frequently anticipated questions:

What does this data set describe?

Title:
GeoTIFF image of the backscatter intensity of the sea floor southwest of Montauk Point, New York, in 1998 (3-m resolution, Mercator, WGS 84)
Abstract:
Surveys of the bathymetry and backscatter intensity of the sea floor south of Long Island, New York, were carried out in November 1998 using a Simrad EM1000 multibeam echosounder mounted on the Canadian Coast Guard ship Frederick G. Creed. The purpose of the multibeam echosounder surveys was to explore the bathymetry and backscatter intensity of the sea floor in several areas off the southern coast of Long Island along the 20-meter isobath. Survey areas offshore of Fire Island Inlet, Moriches Inlet, Shinnecock Inlet, and southwest of Montauk Point were about 1 kilometer (km) wide and 10 km long. The area was mapped by the U.S. Geological Survey with support from the Canadian Hydrographic Service and the University of New Brunswick.
Supplemental_Information:
Other data sets from this survey may be found in Butman and others (2016) (see larger work citation).
  1. How might this data set be cited?
    U.S. Geological Survey, 2016, GeoTIFF image of the backscatter intensity of the sea floor southwest of Montauk Point, New York, in 1998 (3-m resolution, Mercator, WGS 84): data release DOI:10.5066/F7Z899GG, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Butman, Bradford, Danforth, William W., John E. Hughes Clarke, Signell, Richard P., and Schwab, William C., 2016, Bathymetry and backscatter intensity of the sea floor south of Long Island, New York: data release DOI:10.5066/F7Z899GG, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -72.268333
    East_Bounding_Coordinate: -72.114985
    North_Bounding_Coordinate: 40.940000
    South_Bounding_Coordinate: 40.874992
  3. What does it look like?
    mont_backi3m_browse.jpg (JPEG)
    Backscatter intensity image of the sea floor southwest of Montauk Point, New York. File is located in the compressed zip file.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 07-Nov-1998
    Ending_Date: 08-Nov-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 2439 x 4365 x 1, type Pixel
    2. What coordinate system is used to represent geographic features?
      The map projection used is Mercator.
      Projection parameters:
      Standard_Parallel: 40.000000
      Longitude_of_Central_Meridian: -75.000000
      False_Easting: 0.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 3.000000
      Ordinates (y-coordinates) are specified to the nearest 3.000000
      Planar coordinates are specified in meters
      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?
    Entity_and_Attribute_Overview:
    Backscatter intensity, the intensity of the acoustic return from the sea floor from the multibeam system, is a function of the properties of the surficial sediments and of the bottom roughness. Generally high backscatter intensity (strong return), shown as light gray tones, is associated with rock or coarse-grained sediment, and low backscatter intensity (weak return), shown as dark gray tones, with fine-grained sediments. However, the micro-topography, such as ripples, burrows, and benthic populations also affect the reflectivity of the sea floor. Direct observations, using bottom photography or video, and surface samples, are needed to verify interpretations of the backscatter intensity data. The backscatter data have a weak striping that runs parallel to the ship track. Some of the striping is the result of poor data return at nadir that appears as evenly-spaced thin speckled lines. Backscatter intensity is shown as an 8-bit (0-255) grayscale image; 255 is no data.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

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?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Bradford Butman
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA
    USA

    508-548-8700 x2212 (voice)
    bbutman@usgs.gov

Why was the data set created?

This data release makes multibeam echosounder data from the 1998 survey of the sea floor southwest of Montauk Point, New York, available in digital form. The GeoTIFF image of backscatter intensity provides qualitative information on the sediment texture and roughness of the sea floor. Backscatter intensity, a measure of the strength of the acoustic return from the sea floor, is a function of the properties of the surficial sediments and of the bottom roughness. Generally high backscatter intensity (strong return), shown as light gray tones, is associated with rock or coarse-grained sediment, and low backscatter intensity (weak return), shown as dark gray tones, with fine-grained sediments.

How was the data set created?

  1. From what previous works were the data drawn?
    none (source 1 of 1)
    Service, Canadian Hydrographic, Danforth, William W., and John E. Hughes Clarke, Unpublished Material, raw multibeam data.

    Type_of_Source_Media: disc
    Source_Contribution:
    The multibeam data were collected with a Simrad EM1000 multibeam echosounder mounted on the starboard pontoon of the Canadian Coast Guard ship Frederick G. Creed. The 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. The horizontal resolution of the beam on the sea floor is approximately 10 % of the water depth. Vertical resolution is approximately 1 % of the water depth. Data were collected along tracklines oriented approximately northeast-southwest, parallel to the local isobaths, and spaced about 100 m apart. The frequency of the sonar was 95 kHz. Sound velocity profiles were obtained and input into the Simrad processing system to correct for refraction. Navigation was by means of differential GPS. Operation of the Simrad EM1000 was carried out by hydrographers of the Canadian Hydrographic Service. The data were collected on Woods Hole Coastal and Marine Science Center field activity 1998-015-FA.
  2. How were the data generated, processed, and modified?
    Date: 2015 (process 1 of 6)
    A suite of processing software (called SwathEd) (www.omg.unb.ca/~jhc/SwathEd.html), developed by the Ocean Mapping Group at the University of New Brunswick, Canada, was used to process and grid the multibeam bathymetric soundings and backscatter intensity data, and to produce images. The metadata for the bathymetry grid (see link in larger work citation) describes the processing steps applied to the navigation and bathymetric soundings. The following processing steps produced the grayscale image of backscatter intensity for the Montauk data set:
    1. Create a blank 8 bit map file:
    Command line: make_blank mosaic_file
    This command commences a dialog to enable an 8 bit image and input the map boundaries and resolution. The program also prompts for the projection type and parameters to be used creating the binary map file (custom Mercator projection, central longitude of -75 degrees, latitude of true scale 40 degrees north). Then the "blank" file is copied to two files required by the mosaic program:
    Command line: cp mosaic_file.blank mosaic_file.mos
    Command line: cp mosaic_file.blank mosaic_file.ran
    2. Create backscatter files that can be then mosaicked from the backscatter time series:
    Command line: getBeamPattern filename (prefix only)
    Command line: makess -pixel 1.0 -beam_patt beampatt filename (prefix only) output.ss
    Command line: glfill output.ss output.ss_fill (fills in data dropouts).
    3. Mosaic all the backscatter files created in the last step (for each output.ss_fill). Command line: mos2 -autoseam -maxazi 10 -maxdist 10 mosaic_file output.ss_fill
    4. Use a two-point linear contrast stretch (0-254; 255 is no data) to enhance the shaded-relief image:
    Command line: stretchacres -low 170 -high 210 -in mosaic_file -out mosaic_file.stretch Person who carried out this activity:
    U.S. Geological Survey
    Attn: William W. Danforth
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA
    USA

    508-548-8700 x2274 (voice)
    wdanforth@usgs.gov
    Date: 2015 (process 2 of 6)
    Create a TIFF from the backscatter mosaic file using the netpbm utilities (http://netpbm.sourceforge.net/): Command line: rawtopgm -headerskip 1024 image_width image_height mosaic_file.stretch | pnmtoTIFF -none - > mosaic_grayscale.tif Person who carried out this activity:
    U.S. Geological Survey
    Attn: William W. Danforth
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA
    USA

    508-548-8700 x2274 (voice)
    wdanforth@usgs.gov
    Date: 2015 (process 3 of 6)
    Create a TIFF world file (tfw) for the mosaic TIFF image for use in ArcGIS. Copy bounding box and resolution from the jview program output to the .tfw file. Command line: jview mosaic_file.stretch Person who carried out this activity:
    U.S. Geological Survey
    Attn: William W. Danforth
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA
    USA

    508-548-8700 x2274 (voice)
    wdanforth@usgs.gov
    Date: 2016 (process 4 of 6)
    Create GeoTIFF image using the Define Projection Tool in Data Management Tools, Projections and Transformations in ArcToolbox 9.3. Custon projection is Mercator, central meridian of -75.0 degrees, latitude of true scale 40.0 degrees north, false easting 0.0, false northing 0.0; Geographic Coordinate System WGS 1984. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Bradford Butman
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA
    USA

    508-548-8700 x2212 (voice)
    bbutman@usgs.gov
    Date: 20-Jul-2018 (process 5 of 6)
    USGS Thesaurus keywords added to the keyword section. 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
    Date: 10-Aug-2020 (process 6 of 6)
    Added keywords section with USGS persistent identifier as theme keyword. 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?
    Schwab, W.C., Thieler, E.R., Denny, J.F., and Danforth, W.W., 2000, Seafloor sediment distribution off southern Long Island, New York: Open-File Report 00-243, U.S. Geological Survey, Reston, VA.

    Online Links:

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?
  4. Where are the gaps in the data? What is missing?
    This image contains all data collected in the 1998 multibeam survey southwest of Montauk Point. There are a few gaps in the image due to incomplete coverage by the multibeam system. Other data sets collected offshore of Long Island, New York, on WHCMSC field activity 1998-015-FA may be found in Butman and others (2016) (see larger work citation).
  5. How consistent are the relationships among the observations, including topology?
    All data were processed in the same manner. Some features in the multibeam data are artifacts of data collection and environmental conditions. They include unnatural-looking features and patterns oriented parallel or perpendicular to survey tracklines. The orientation of the survey tracklines is often identified in the image by parallel stripes of false high reflectivity that occur at nadir. GPS position data began to degrade on line 3045 and went out completely on line 3047. GPS data were regained on line 3048. The loss of navigation resulted in a data offset on lines 3045-3047. The offset is not corrected. The Long Island surveys were assigned a block of line numbers beginning with 3000.

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 None
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center
    Denver, CO
    USA

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? mont_backi3m.zip: contains mont_backi3m.tif, mont_backi3m.tfw, and associated FGDC-compliant metadata (CSDGM format).
  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?
    The GeoTIFF image of backscatter intensity is compressed into a WinZip (version 14) file (mont_backi3m.zip). To use these data, the user must have software capable of uncompressing the zip file and ArcGIS or another GIS application package capable of viewing the data.

Who wrote the metadata?

Dates:
Last modified: 19-Mar-2024
Metadata author:
U.S. Geological Survey
Attn: Bradford Butman
384 Woods Hole Road
Woods Hole, MA

508-548-8700 x2212 (voice)
whsc_data_contact@usgs.gov
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is no longer with USGS. (updated on 20240319)
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_F7Z899GG/mont_backi3m_meta.faq.html>
Generated by mp version 2.9.51 on Wed Jun 26 15:25:02 2024