Bathymetry of the Sandy Hook artificial reef (2-m resolution Esri binary grid and 32-bit GeoTIFF, Mercator, WGS 84)

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Frequently anticipated questions:


What does this data set describe?

Title:
Bathymetry of the Sandy Hook artificial reef (2-m resolution Esri binary grid and 32-bit GeoTIFF, Mercator, WGS 84)
Abstract:
The Sandy Hook artificial reef, located on the sea floor offshore of Sandy Hook, New Jersey was built to create habitat for marine life. The reef was created by the placement of heavy materials on the sea floor; ninety-five percent of the material in the Sandy Hook reef is rock. In 2000, the U.S. Geological Survey surveyed the area using a Simrad EM1000 multibeam echosounder mounted on the Canadian Coast Guard (CCG) ship Frederick G. Creed. The purpose of this multibeam survey, done in cooperation with the U.S. Army Corps of Engineers when the Creed was in the New York region in April 2000, was to map the bathymetry and backscatter intensity of the sea floor in the area of the Sandy Hook artificial reef. The collected data from this cruise are bathymetry, backscatter intensity, and navigation trackline.
Supplemental_Information:
Other datasets from the 2000 survey of the Sandy Hook artificial reef may be found in Butman and others (2017) (see larger work citation). For more information on the field activity that collected these data, see the field activity page https://cmgds.marine.usgs.gov/fan_info.php?fa=2000-015-FA.
  1. How might this data set be cited?
    U.S. Geological Survey, and U.S. Army Corps of Engineers, 2017, Bathymetry of the Sandy Hook artificial reef (2-m resolution Esri binary grid and 32-bit GeoTIFF, Mercator, WGS 84): data release DOI:10.5066/F74F1PNH, 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 Sandy Hook artificial reef, offshore of New Jersey: data release DOI:10.5066/F74F1PNH, 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 Sandy Hook artificial reef, offshore of New Jersey: U.S. Geological Survey data release, https://doi.org/10.5066/F74F1PNH.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -73.953345
    East_Bounding_Coordinate: -73.924982
    North_Bounding_Coordinate: 40.400009
    South_Bounding_Coordinate: 40.336665
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/59b2b99be4b020cdf7dc141c?name=shreef_bath2m_browsegraphic.jpg (JPEG)
    Browse graphic of the bathymetry of the Sandy Hook artificial reef.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 23-Apr-2000
    Ending_Date: 24-Apr-2000
    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 3536 x 1211 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 2.000000
      Ordinates (y-coordinates) are specified to the nearest 2.000000
      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:
    2-m resolution 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 -7 m to -20 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
    • 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
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x 2212 (voice)
    bbutman@usgs.gov

Why was the data set created?

The bathymetry shows the shape of the sea floor. Of particular interest are the changes in water depth associated with the artificial reef.

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 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 Sandy Hook artificial reef area was surveyed in a Zamboni pattern (for efficient turns at high speed) with lines running north-south. The Zamboni pattern yields blocks of northward-run lines adjacent to blocks of southward-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 2000-015-FA (https://cmgds.marine.usgs.gov/fan_info.php?fa=2000-015-FA).
  2. How were the data generated, processed, and modified?
    Date: 2000 (process 1 of 6)
    Processing of the data at sea 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 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), backscatter intensity 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)
    bdanforth@usgs.gov
    Date: 2017 (process 2 of 6)
    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 2 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. The solution is: weight_depth/weights for each node.
    First a blank binary grid and the weights and weight_depth files must be created (user specifies bounds of map sheet, floating point or integer, cell size) :
    Command line: make_blank -float gridFile
    This command commences a dialog to 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 Sandy Hook reef data was created with a grid node spacing of 2 meters, a cutoff radius of 6 meters, and an inner radius to the weighting function of 2 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 2 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)
    bdanforth@usgs.gov
    Date: 2017 (process 3 of 6)
    Data were edited and processed to produce final grids and images of the data. Steps 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; see cross reference). 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 NAVD88.
    Command line (tides): mergeTide -tide BinaryTideFile filename.merged
    4. Correct outer beams for depth offset caused by error in EEPROM programming (see Logical Consistency Report)
    Command line: deHump -depscale 0.0105 filename.merged
    5. Create a new 2 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 2 gridFile filename.merged
    6. Convert binary bathymetric grid to Esri ASCII raster format:
    Command line: r4toASCII gridFile.r4
    This creates a file called gridFile.asc. 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: 2017 (process 4 of 6)
    An Esri bathymetry grid was created by importing data from ASCII raster format into Esri grid format using ArcToolbox (ArcGIS 9.3) conversion tool ASCII to Raster. 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: 2017 (process 5 of 6)
    The SwathEd processing software produced depth as positive values. Change depth from positive to negative using the raster calculator in Spatial Analyst (ArcGIS 9.3). Multiply shreef_bath2m grid by -1. 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
    Data sources used in this process:
    • shreef_bath2m
    Data sources produced in this process:
    • shreef_bath2m
    Date: 2017 (process 6 of 6)
    The Esri binary grid was exported from an ArcMap 10.3.1 document as a 32-bit GeoTIFF image. The extent, spatial reference, and cell size were set to the original raster dataset. 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?
    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: Coastal and Estuarine Studies Series v. 48, American Geophysical Union Press, Washington, D.C..

    Westerink, J.J., Luettich, R.A., Jr., and Mucini, J.S., 1994, Modeling tides in the western North Atlantic using unstructured graded grids: Tellus 46(2), International Meteorological Institute, Stockholm, Sweden.

    Online Links:

    • DOI:10.1034/j.1600-0870.1994.00007.x

    New Jersey Division of Fish and Wildlife, Unknown, Sandy Hook Reef.

    Online Links:

    New Jersey Department of Environmental Protection, Division of Fish and Wildlife, 2017, Artificial Reef Program.

    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?
    All data from the multibeam survey of the Sandy Hook artificial reef are included in the mosaic. There are a few gaps in the image due to incomplete coverage by the multibeam system.
  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 parallel stripes in the data. 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 depths were corrected post-acquisition by a SwathEd program called dehump, which pulls up the outer beams. There are some anomalies in water depth, of unknown origin, visible along portions of track line 2116 (water appears too deep by about 0.5 m) and trackline 2124 (water appears too shallow by about 0.4 m).

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
    Federal Center
    Denver, CO

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? shreef_bath2m.zip: contains the Esri binary grid of bathymetry data (shreef_bath2m), comprised of the shreef_bath2m folder and an info folder, the 32-bit GeoTIFF and world file of the bathymetry (shreef_bath2m.tif and shreef_bath2m.tfw), browse graphic (shreef_bath2m_browsegraphic), 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 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 U.S. Geological Survey 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 bathymetric grid and associated metadata from the Sandy Hook artificial reef survey are available in a zip file (shreef_bath2m.zip). The grid data are stored in an Esri 32-bit floating point binary grid. 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: 27-Sep-2017
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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