GeoTIFF image of the backscatter intensity of the sea floor of the Historic Area Remediation Site in 1996 (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 of the Historic Area Remediation Site in 1996 (3-m resolution, Mercator, WGS 84)
Abstract:
Surveys of the bathymetry and backscatter intensity of the sea floor of the Historic Area Remediation Site (HARS), offshore of New York and New Jersey, were carried out in 1996, 1998, and 2000 using a Simrad EM1000 multibeam echosounder mounted on the Canadian Coast Guard ship Frederick G. Creed. The objective of the multiple echosounder surveys was to map the bathymetry and surficial sediments over time as dredged material was placed in the HARS to remediate contaminated sediments. Maps derived from the multibeam surveys show sea-floor bathymetry, shaded-relief bathymetry, and backscatter intensity (a measure of sea-floor texture and roughness) at a spatial resolution of 3 meters. The area was mapped by the U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers and with support from the Canadian Hydrographic Service and the University of New Brunswick.
Supplemental_Information:
This is Edition 2.0 of GeoTIFF Hars1996Mos.tif. An error in the University of New Brunswick (Clarke, 1998, see cross reference) processing software that resulted in the multibeam observations not being properly projected onto a plane was discovered in 2003. A second error in the gridding algorithm was discovered in 2007, requiring a shift of 1/2 grid cell to northwest. Edition 2.0 differs from Edition 1.0 (Butman and others, 2002) in that it was processed using corrected software; comparison of the location of selected features suggests that Edition 2.0 is shifted approximately 10 m to the east compared to Edition 1.0. In addition, the stretch used to create the 8-bit image is 0-254 and the value 255 is no data. In Edition 1.0, the stretch is 0-255 and the value 255 is also no data. Maps and interpretations of these data are available in Butman and others (2002), Butman (2002), and Butman and others (2003) (citations in cross references). Other datasets from the 1996 HARS survey, as well as datasets from surveys of the HARS in 1998 and 2000, may be found in Butman and others (2017) (see larger work citation).
  1. How might this data set be cited?
    U.S. Geological Survey, and U.S. Army Corps of Engineers, 2017, GeoTIFF image of the backscatter intensity of the sea floor of the Historic Area Remediation Site in 1996 (3-m resolution, Mercator, WGS 84): data release DOI:10.5066/F74B2ZGX, 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, and Signell, Richard P., 2017, Bathymetry and backscatter intensity of the sea floor of the Historic Area Remediation Site in 1996, 1998, and 2000: data release DOI:10.5066/F74B2ZGX, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Butman, Bradford, Danforth, W.W., Clarke, J.E.H., and Signell, R.P., 2017, Bathymetry and backscatter intensity of the sea floor of the Historic Area Remediation Site in 1996, 1998, and 2000: U.S. Geological Survey data release, https://doi.org/10.5066/F74B2ZGX.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -73.900000
    East_Bounding_Coordinate: -73.812488
    North_Bounding_Coordinate: 40.433333
    South_Bounding_Coordinate: 40.350008
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/588103cde4b00a062355a507/?name=Hars1996Mos_browse.jpg (JPEG)
    Browse graphic of the backscatter intensity of the sea floor.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 23-Nov-1996
    Ending_Date: 27-Nov-1996
    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 3102 x 2491 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, 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, is associated 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´s track. Some of the striping is the result of poor data return at nadir that appears as evenly-spaced thin speckled lines. Some striping may also be due to critical angle effects, where the intensity of return varies as a function of the angle of incidence of the incoming sound on the sea floor. 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
    • U.S. Army Corps of Engineers
  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?

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, is associated 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 spaced 5-7 times the water depth apart at a speed of 10-14 knots. The HARS was surveyed in a Zamboni pattern (for efficient turns at high speed) with lines running north-south. The Zamboni pattern yields blocks of southward-run lines adjacent to blocks of northward-run lines. 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 1996-043-FA (https://cmgds.marine.usgs.gov/fan_info.php?fa=1996-043-FA).
  2. How were the data generated, processed, and modified?
    Date: 2015 (process 1 of 6)
    A suite of processing software (called SwathEd) (Clarke, 1998; see cross reference), developed by the Ocean Mapping Group at the University of New Brunswick, Canada, was used to process the multibeam backscatter intensity data and produce images. An error in the University of New Brunswick (Clarke, 1998, see cross reference) processing software that resulted in the multibeam observations not being properly projected onto a plane was discovered in 2003. A second error in the gridding algorithm was discovered in 2007, requiring a shift of 1/2 grid cell to northwest. This processing step uses the corrected software. The following processing steps produced the grayscale image of backscatter intensity for the 1996 HARS 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, 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 180 -high 220 -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)
    bdanforth@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)
    bdanforth@usgs.gov
    Date: 2015 (process 3 of 6)
    Create a TIFF world file (tfw) for the mosaic TIFF image for import to 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)
    bdanforth@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. Custom 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: 07-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?
    Butman, Bradford, Danforth, W.W., Knowles, S.C., May, Brian, and Serrett, Laurie, 2002, Seafloor topography and backscatter intensity of the Historic Area Remediation Site (HARS), offshore of New York, based on multibeam surveys conducted in 1996, 1998, and 2000: Open-File Report 00-503, U.S. Geological Survey, Reston, VA.

    Online Links:

    Butman, Bradford, 2002, Mapping the sea floor of the Historic Area Remediation Site (HARS) offshore of New York City: Fact Sheet FS-001-02, U.S. Geological Survey, Reston, VA.

    Online Links:

    Butman, Bradford, Middleton, T.J., Thieler, E.R., and Schwab, W.C., 2003, Topography, shaded-relief, and backscatter intensity of the Hudson Shelf Valley, Offshore of New York: Open-File Report 03-372, U.S. Geological Survey, Reston, VA.

    Online Links:

    Butman, Bradford, Alexander, P. Soupy, Harris, C.K., Traykovski, P.A., ten Brink, M.B., Lightsom, F.S., and Martini, M.A., 2003, Oceanographic observations in the Hudson Shelf Valley, December 1999 - April 2000: Data Report: Open-File Report 02-217, U.S. Geological Survey, Reston, VA.

    Online Links:

    Clarke, J.H., 1998, SwathEd: Ocean Mapping Group, University of New Brunswick, New Brunswick, Canada.

    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) which is typically accurate to +/- 3 meters, horizontally. To qualitatively assess the horizontal accuracy of the three HARS surveys, the locations of 23 distinct features on the sea floor identified in the 1996, 1998, and 2000 shaded-relief images were compared. Offsets of features in the 1996 survey compared to the 1998 survey were typically 5 m or less, as expected when navigating with DGPS. Offsets of features in the 2000 survey compared to the 1998 survey were 10-20 m and to the north or south, the along-track direction of the survey. For 18 of the 23 features in the 2000 survey, offsets were to the north compared to the 1998 survey when the track in 2000 was to the south, and offsets were to the south compared to the 1998 survey when the track in 2000 was to the north. The offsets of the remaining 5 features, all surveyed on Julian Day 115, were in the direction of the survey track in 2000. The HARS surveys were run in a Zamboni pattern which resulted in blocks of adjacent survey lines running in the same direction; thus consistent offsets appear to shift these blocks north or south depending on the direction the lines were run. The cause of the offsets in the 2000 survey is unknown and no correction has been made for them.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This image represents all backscatter intensity data collected in the Historic Area Remediation Site on WHCMSC field activity 1996-043-FA. There are a few data gaps in the image due to incomplete coverage by the multibeam system. The 1996 survey did not cover a strip approximately 900 m wide on the western side of the HARS. Other datasets from the 1996 HARS survey may be found in Butman and others (2017) (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 backscatter intensity 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 tracklines is sometimes identified by the faint parallel stripes in the image.

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

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? Hars1996Mos.zip: contains Hars1996Mos.tif, Hars1996Mos.tfw, browse graphic, 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 U.S. Geological Survey, nor the U.S. Army Corps of Engineers, 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 zip file (Hars1996Mos.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: 07-Aug-2020
Metadata author:
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
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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