Grid of the sea-floor bathymetry offshore of Fire Island Inlet, New York, in 1998 (3-m resolution Esri binary grid, Mercator, WGS 84)

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Frequently anticipated questions:


What does this data set describe?

Title:
Grid of the sea-floor bathymetry offshore of Fire Island Inlet, New York, in 1998 (3-m resolution Esri binary grid, 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, Grid of the sea-floor bathymetry offshore of Fire Island Inlet, New York, in 1998 (3-m resolution Esri binary grid, 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 10.5066/F7Z899GG, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -73.250000
    East_Bounding_Coordinate: -73.079999
    North_Bounding_Coordinate: 40.639992
    South_Bounding_Coordinate: 40.570000
  3. What does it look like?
    fire_bath3m_browse.jpg (JPEG)
    Image of sea-floor bathymetry offshore of Fire Island Inlet, New York. File is located in the compressed zip file.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 06-Nov-1998
    Ending_Date: 07-Nov-1998
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: 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 2614 x 4839 x 1, type Grid Cell
    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.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Implicit coordinate
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    3-m resolution ESRI binary grid of sea floor elevation (in meters) referenced to NAVD88. The soundings were corrected for tidal fluctuations using the ADCIRC tidal model. The model produces harmonic constituents and a mean component relative to the NAVD88 datum. Correcting survey water levels using ADCIRC-predicted water levels are thus relative to NAVD88 datum. Deviation from the NAVD88 datum will be due errors in the ADCIRC correction, other fluctuations in sea level during the survey, and deviation of mean sea level from NAVD88 due to ocean dynamics. Depth is reported as negative altitude. Range is -16.3 m to -23.2 m.
    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 offshore of Fire Island Inlet, New York, available in digital form. The bathymetry shows the shape of the sea floor. Of particular interest were the size, shape, and orientation of bed forms that may indicate sediment movement.

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: 1998 (process 1 of 7)
    Processing of the data was carried out by USGS personnel with assistance from the Ocean Mapping Group at the University of New Brunswick (UNB), Canada. A suite of processing software (called swathed) developed by the Ocean Mapping Group (<www.omg.unb.ca/~jhc/SwathEd.html>) was used to process, edit, and archive the bathymetric soundings. These routines are designed to be run on a Unix and/or Linux operating system. The processing and editing steps carried out on board the ship were:
    
    
    1. Demultiplex (unravel) the Simrad data files using RT to generate separate files for a given raw file (filename.raw_all) containing navigation (filename.nav), depth soundings (filename.merged), sidescan sonar backscatter values (filename.merged_ssdata), acquisition parameters (filename.param) sound velocity at the transducer (filename.sv_tdcr) and sound velocity profiler information (filename.svp). ? Command line: RT -packdown -background -WRITE -em1000 -CnC -prefix RawFiles/ -suffix _raw.all -out ProcessedFiles/InputFilenamePrefix InputFilenamePrefix
    
    
    2. Edit the navigation data on-screen using the SwathEd routine jview to remove undesirable points, including turns at the ends of survey lines. Jview also rejects stray GPS fixes outside of the survey area, as set by the operator.
    
    
    Command line: jview -rejectnav -navedit filename.nav
    
    
    3. Make a copy of the edited navigation, and then create a new navigation file that has the bad fixes deleted from it.
    
    
    Command line: mv filename.nav filename.nav_all
    
    
    Command line: appendNav -goodonly -comp filename.nav filename.nav_all
    
    
    4. Merge the edited navigation back into the file containing the depth soundings using just the prefix of the filename. The location of the antenna relative to the motion reference unit is also entered here, along with a maximum time gap (in seconds) allowed between navigation fixes.
    
    
    Command line: mergeNav -ahead 5.379 -right 3.851 -below 4.244 -time_limit 300 filename
    
    
    5. Edit the multibeam soundings for each trackline. SwathEd displays blocks of data across and along the trackline. Anomalous points were identified by comparison to other points and by an understanding of the sea floor geology and morphology. Anomalous soundings were removed.
    
    
    Command line: swathed filename.merged 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: 2010 (process 2 of 7)
    Map the bathymetric soundings from each processed data file onto a digital terrain model (DTM) in the Mercator projection using weigh_grid with grid nodes spaced at 3 meters. The weigh_grid program creates a DTM by summing up the weighted contributions of all the provided data into the DTM. The weighted contributions only extend to a user defined region around the true location of the estimate (the cutoff). The weight of an individual point contribution decays away from the node location based on the order of the Butterworth (inverse weighting) filter (-power n), the width of the flat topped radius of the weighting function (-lambda n.n), and the absolute cutoff limit (-cutoff) that will be used for data points contributing to a node. In addition, each beam/other value can be pre-weighted if required to account for its reliability. A custom weight file for each beam is created by hand and input into the weigh_grid program using the -custom_weight option. Three files are created which are used by the weigh_grid program. An ".r4" file, which contains the grid node values in binary format, an "r4_weights" file, and an "r4_weight_depth" file. To do the summing of the weights, the .r4_weights file contains the sums of the weights for each data point contributing to the node, and the .r4_weight_depth file contains the sum of the weights x the depths. Naturally the solution is: weight_depth/weights for each node. For more information, visit the OMG website at <http://www.omg.unb.ca>.
    
    
    First a blank binary grid and the weights and weight_depth files must be created:
    
    
    Command line: make_blank -float gridFile
    
    
    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). The next command creates the weights and weight_depth files associated with the binary grid:
    
    
    Command line: tor4 gridFile
    
    
    These two steps create all three files with a gridFile prefix.
    
    
    Next, each individual data file (.merged suffix) is added to the grid using weigh_grid. The grid of the Fire Island data was created with a grid node spacing of 3 meters, a cutoff radius of 6 meters, and an inner radius to the weighting function of 1.5 meters:
    
    
    Command line: weigh_grid -omg -tide -coeffs -mindep -2 -maxdep -800 -beam_mask -beam_weight -custom_weight EM1000_Weights -butter -power 2 -cutoff 6 -lambda 1.5 gridFile filename.merged 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: 2010 (process 3 of 7)
    Processing to further edit and correct the data and to produce final grids and images of the data included:
    
    
    1. Correct errors in soundings due to sound refraction, caused by variations in sound velocity profile, using the SwathEd refraction tool. These artifacts can be recognized in a cross-swath profile of a relatively flat patch of sea floor. When viewing the swath data across a profile, the sea floor will appear to have a "frown" or "smile" when in fact the data should be flat across the profile. Insufficient and/or erroneous sound velocity information, which is usually due to widely spaced or non-existent velocity profiles within an area, results in an under or over-estimate of water depth which increases with distance from the center of the swath. For a discussion of how this effect can be recognized in a swath bathymetric data file, see < http://www.omg.unb.ca/AAAS/UNB_Seafloor_Mapping.html>.
    
    
    2. Remove erroneous soundings that were not edited in the field using the SwathEd program.
    
    
    3. The measured elevations were adjusted for tidal fluctuations by subtracting tidal elevations and mean sea level predicted by the ADCIRC tidal model (Westerink and others 1994; Luettich and Westerink, 1995). A MATLAB script was used to interpolate the ADCIRC constituents along the ship track and then calculate the tidal elevation and mean sea level at the time of the survey. The vertical datum of the ADCIRC correction is NAVD88.
    
    
    Using the adjusted tidal elevations, create a binary tide file to be using in merging the tidal heights with the bathymetric soundings.
    
    
    Command line: binTide -year YYYY asciiTideFile BinaryTideFile
    
    
    The program mergeTide brings the swath soundings to the NAVD88 datum and corrected for predicted tide:
    
    
    Command line (tides): mergeTide -tide BinaryTideFile filename.merged
    
    
    4. Create a new 3 meter grid of the bathymetric soundings using the SwathEd routine weighgrid.
    
    
    Command line: weigh_grid -fresh_start -omg -tide -coeffs -mindep -2 -maxdep -800 -beam_mask -beam_weight -custom_weight EM1000_Weights -butter -power 2 -cutoff 6 -lambda 1.5 gridFile filename.merged
    
    
    5. Convert binary bathymetric grid to Esri ASCII raster format:
    
    
    Command line: r4toASCII gridFile.r4
    
    
    This creates a file called gridFile.asc.
    
    
    References cited:
    
    
    Westerink, J.J., R.A. Luettich, Jr. and J. Muccino, 1994, Modeling Tides in the Western North Atlantic Using Unstructured Graded Grids: Tellus, v. 46a(2), p. 178-199.
    
    
    Luettich, R.A., Jr. and Westerink, J.J. , 1995, Continental Shelf Scale Convergence Studies with a Barotropic Tidal Model, Quantitative Skill Assessment for Coastal Ocean Models, in Lynch, D. and Davies, A. [eds.], Coastal and Estuarine Studies series, v. 48, p. 349-371, American Geophysical Union Press, Washington, D.C. 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: 2010 (process 4 of 7)
    An Esri bathymetry grid was created by importing data from ASCII raster format into Esri grid format. 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: 2014 (process 5 of 7)
    Change depth from positive to negative using the Negate function in ArcToolbox - Spatial Analyst Tools - Math - Trigonometric (ArcGIS 9.3). The SwathEd processing software produced depth as positive values. Person who carried out this activity:
    Bradford Butman
    U.S. Geological Survey
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA
    USA

    508-548-8700 x2212 (voice)
    bbutman@usgs.gov
    Data sources produced in this process:
    • fire_bath3m
    Date: 20-Jul-2018 (process 6 of 7)
    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: 24-Sep-2021 (process 7 of 7)
    Added keywords section with USGS persistent identifier as theme keyword, 20200810. Removed space in originator name, 20210924. 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?
    These data have been corrected for vessel motion (roll, pitch, heave, yaw). The theoretical vertical resolution of the Simrad EM-1000 multibeam echosounder is 1% of water depth, approximately 0.2 m within the study area. The soundings were also corrected for tidal fluctuations using the ADCIRC tidal model. The model produces harmonic constituents and a mean component relative to the NAVD88 datum. Correcting survey water levels using ADCIRC-predicted water levels are thus relative to NAVD88 datum. Deviation from the NAVD88 datum will be due errors in the ADCIRC correction, other fluctuations in sea level during the survey, and deviation of mean sea level from NAVD88 due to ocean dynamics.
  4. Where are the gaps in the data? What is missing?
    This image contains all data collected in the multibeam survey offshore of Fire Island Inlet, New York, in 1998. There are a few gaps in the grid 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 small highs and lows and unnatural-looking features, and patterns oriented parallel or perpendicular to survey tracklines. The orientation of the tracklines is sometimes identified by faint parallel stripes in the image. During data acquisition, the electrically erasable programmable read only memory (EEPROM) within the transceiver that controls the beam launch angles was programmed with incorrect parameters for the outer ten beams on the port and starboard sides. This caused depth soundings to be deeper for these outer beams by approximately 0.1 m; these deeper soundings are 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: These data are not to be used for navigation purposes.
  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? fire_bath3m.zip: contains the Esri binary grid fire_bath3m, comprised of the fire_bath3m folder and an info folder, 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 grid of bathymetry is compressed into a WinZip (version 14) file (fire_bath3m.zip). To utilize these data, the user must have software capable of uncompressing the zip file and importing and viewing an Esri ArcRaster grid. The grid consists of two folders, one with the "grid name," and one "info" folder. The two folders must be uncompressed to the same folder.

Who wrote the metadata?

Dates:
Last modified: 24-Sep-2021
Metadata author:
U.S. Geological Survey
Attn: Bradford Butman
384 Woods Hole Road
Woods Hole, MA

508-548-8700 x2212 (voice)
bbutman@usgs.gov
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/fire_bath3m_meta.faq.html>
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