FI_BATHYGRD: 10-meter swath bathymetric grid collected by the U.S. Geological Survey offshore of Fire Island, NY in 2011 (UTM Zone 18N, WGS 84, Esri Binary Grid)

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Frequently-anticipated questions:

What does this data set describe?

FI_BATHYGRD: 10-meter swath bathymetric grid collected by the U.S. Geological Survey offshore of Fire Island, NY in 2011 (UTM Zone 18N, WGS 84, Esri Binary Grid)
The U.S. Geological Survey (USGS) mapped approximately 336 square kilometers of the lower shoreface and inner-continental shelf offshore of Fire Island, New York in 2011 using interferometric sonar and high-resolution chirp seismic-reflection systems. This report presents maps of bathymetry, acoustic backscatter, the coastal plain unconformity, the Holocene marine transgressive surface and modern sediment thickness. These spatial data support research on the Quaternary evolution of the Fire Island coastal system and provide baseline information for research on coastal processes along southern Long Island.

More information about this field activity and the data collected can be found at the Field Activity Web Page (<>)

  1. How should this data set be cited?

    U.S. Geological Survey, 2014, FI_BATHYGRD: 10-meter swath bathymetric grid collected by the U.S. Geological Survey offshore of Fire Island, NY in 2011 (UTM Zone 18N, WGS 84, Esri Binary Grid): Open-File Report 2014-1203, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts.

    Online Links:

    This is part of the following larger work.

    Schwab, William C. , Denny, Jane F. , and Baldwin, Wayne E. , 2014, Maps Showing Bathymetry and Modern Sediment Thickness on the Inner- Continental Shelf Offshore of Fire Island, New York: pre-Hurricane Sandy: Open-File Report 2014-1203, U.S. Geological Survey, Coastal and Marine Geology Program, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -73.280193
    East_Bounding_Coordinate: -72.738989
    North_Bounding_Coordinate: 40.758503
    South_Bounding_Coordinate: 40.536355

  3. What does it look like?

    <> (JPEG)
    Depth-colored image of bathymetry on the inner-continental shelf offshore of Fire Island, NY

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 20-May-2011
    Ending_Date: 08-Jun-2011
    ground condition during 20110520 - 20110523, 20110525 - 20110601; 20110604 - 20110608.

  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 2365 x 4525 x 1, type Grid Cell

    2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 18
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -75.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 10.000000
      Ordinates (y-coordinates) are specified to the nearest 10.000000
      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.

      Depth_Datum_Name: NAVD88
      Depth_Resolution: 0.1 meters
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    Depth in meters relative to NAVD88 (Source: Esri)

    Swath bathymetry in Esri ArcRaster format. Data values represent depth in meters referenced to North American Vertical Datum of 1988 (NAVD88).
    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)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    Jane F. Denny
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, Massachusetts 02543

    508-548-8700 x 2311 (voice)
    508-457-2310 (FAX)

Why was the data set created?

This grid represents approximately 2800 line kilometers of bathymetric data collected in 2011. These data were collected using an interferometric sonar (Systems Engineering and Assessment Ltd. (SEA) SWATHplus-M (234 kHz)) by the U.S. Geological Survey during USGS survey 2011-005-FA. These bathymetric data were used to define the morphology of the sea floor on the inner-continental shelf offshore of Fire Island, New York to help assess environmental change caused by natural processes and human activities.

How was the data set created?

  1. From what previous works were the data drawn?

    none (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, Raw Bathymetric Data.

    Type_of_Source_Media: online
    Survey: Survey lines were run at an average speed of 5 knots. Lines 1 through 27 were run at a 75-m line spacing to achieve full coverage of the seafloor in a priority area of interest in the nearshore, in water depths less than 15 meters. Lines 28 through 109 were run at a 150-m line spacing, with the exception of tie lines (lines 52 through 60, 65 through 67, 89 through 92), which were run at approximately a 2-km line spacing.

    Sonar: Swath-bathymetric and acoustic-backscatter data were acquired with a SEA, Ltd., SWATHplus-M interferometric sonar operating at a frequency of 234 kHz and a variable range (increased or decreased manually depending on water depth). The system was operated with a transmit power: 80 percent, 4096 samples per channel, and a variable range (increased or decreased depending on water depth). The SWATHplus-M was mounted on the port side of the M/V Scarlett Isabella during survey operations. A Coda Octopus F180R Attitude and Positioning system recorded ship motion (heave, pitch, roll, and yaw). These data were transmitted via network connection to the SWATHplus-M acquisition software. The Octopus F180R Inertial Measurement Unit (IMU) was mounted directly above the SEA SWATHplus-M transducers, to minimize lever arm offsets that can lead to positioning errors. The F180R uses two L1 antennas for position and heading accuracy. The antennas are mounted on a rigid horizontal pole, positioned at the top of the sidemount, with a horizontal separation of 1 meter and are offset from the IMU in a forward/aft configuration. The forward offset of the primary antenna from the IMU is 0.5 meters, with no port/starboard offset.

    Sound Velocity Profiles: 135 sound velocity profiles were acquired during survey operations at roughly 1 to 3 hour intervals using an Odim MVP30 motion vessel profiler. The MVP30 failed during survey operations. Sound velocity profiles were only collected during JD141 through 143 (lines 1 through 27).

    While much effort was devoted to cleaning the data and minimizing survey artifacts, some artifacts may still be seen in the final gridded data including an along track artifact at nadir (the ship track) and at the far edges of a survey line where adjacent swaths overlap. These artifacts are especially noticeable in areas of little local relief.

    More information about this field activity and the data collected can be found at the Field Activity Web Page (<>)

  2. How were the data generated, processed, and modified?

    Date: 2014 (process 1 of 4)
    Converting Raw (SXR) to Field-Processed (SXP) Files: Raw SXR bathymetry data were acquired with the SEA SWATHplus acquisition software (version 3.07) and used to generate field-processed SEA SWATHplus SXP files. The following information was stored within the SWATHplus session files and applied to the raw bathymetric soundings: 135 sound velocity profiles to minimize refraction artifacts due to fluctuations from the speed of sound in the water column (lines 1 - 27 only; no corrections were applied to lines 28 - 109 due to MVP30 system failure), roll offsets calculated during pre-survey patch test, draft of the transducer below the water line, and the measured angles and relative positions of the swath bathymetric transducers. The SWATHplus acquisition software applies the pitch, roll, heave, yaw and heading data supplied by the F180R IMU, to compensate depth solutions across the swath for any ship motion. Several bathymetric filters were applied to remove erroneous soundings and reduce the density of the data. Bathymetric filtering typically included low amplitude (110%), range (0-3m), phase confidence (55%), box (2 -40m depth, 0.5 -75m horizontal), median (window size 5), water column (10%), alongtrack 1 (depth difference of 3-m, window size 3-m, and learn rate of 0.6), and mean filters (0.25m). These represent the typical parameters used for the majority of the USGS survey although the values may have been adjusted slightly for specific parts of the survey area.

    Jane F. Denny performed this and all subsequent process steps.

    Person who carried out this activity:

    Jane F. Denny
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, Massachusetts 02543

    508-548-8700 x 2311 (voice)
    508-457-2311 (FAX)

    Date: 2014 (process 2 of 4)
    Navigation: Tide files were created during post-processing using one- or two-minute interval averages of the RTK tide data recorded in the "TID" message string of the HYPACK navigation file for each line. The TID messages from DEV 1 (which was the NovAtel DL-V3 receiver) were used to extract the tide offset values using a shell script called getNovatelTides and an AWK script called parseHypackNovatelTides.awk

    Date: 2014 (process 3 of 4)
    Processing data within CARIS: A new CARIS HIPS project (version 7.1) was created with projection information set to Universal Transverse Mercator (UTM) Zone 18N, WGS84. Each SWATHPlus processed file (sxp) was imported to the new CARIS project using the Import/Conversion Wizard. A 5 meter resolution Bathymetric and Statistical Error (BASE) Surface was created and reviewed for any inconsistencies or data anomalies. Navigation was reviewed and edited as needed using the navigation editor tool. A 'tide' file, representing water elevations referenced to NAVD88, was loaded into CARIS and merged with each line to apply a correction for tidal variations throughout the survey. The BASE surface was recomputed to incorporate the new tide information. Beam-to-beam slopes and across track angle filters were applied to the soundings line by line and each line was further hand-edited using Swath Editor. The refraction editor was used to adjust sound speed values in areas where velocimeter data did not adequately correct for changes in the speed of sound through the water column (lines 1 - 27), or where no velocimeter data were collected (lines 28 - 109).

    The final surface was exported in ASCII format (xyz - easting, northing, depth) using the Export Wizard, Export BASE Surface to ASCII.

    Date: 2014 (process 4 of 4)
    ArcGIS: ArcGIS 9.3.1, Tools, Add XY data (WGS 1984, UTM, Zone 18N) was used to add the data as an event theme to the ArcGIS project file. The event theme was loaded into the view and then exported (Data - Export Data) as a shapefile. Spatial Analyst, Interpolation, Natural Neighbor was then used to generate a 10-m interpolated surface. Depths in the resulting grid were positive values. To convert these to negative depths, Raster Calculator was used (grid * -1) and the output saved. The output grid was then clipped using a bounding polygon representing the survey bounds (Spatial Analyst, Extraction, Extract by Mask), created the final bathymetric grid: fi_bathygrd.

  3. What similar or related data should the user be aware of?

    Schwab, William C. , Baldwin, Wayne E. , Hapke, Cheryl J. , Lentz, Erika E. , Gayes, Paul T. , Denny, Jane F. , List, Jeffrey H. , and Warner, John C. , 2013, Geologic Evidence for Onshore Sediment Transport from the Inner Continental Shelf: Fire Island, New York: Journal of Coastal Research Volume 29, Issue 3, pp. 526-544., Coastal Education and Research Foundation, Inc., Florida, USA.

    Online Links:

    Foster, David S. , Swift, Ann B. , and Schwab, William C. , 1999, Stratigraphic Framework Maps of the nearshore area of southern Long Island from Fire Island to Montauk Point, NY: Open-File Report 99-559, U.S. Geological Survey, Reston, VA.

    Online Links:

    Schwab, William C. , Thieler, E. Robert , Denny, Jane F. , Danforth, William W. , and Hill, Jenna C. , 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?

    Navigation was acquired with Differential Global Positioning System and Wide Area Augmentation System (DGPS+WAAS), which is accurate to + or - 1 to 2 meters, horizontally. The forward, or primary, Coda Octopus F180R Attitude and Positioning system antenna was used to acquire DGPS data and transmit via a network connection to the SEA SWATHplus data acquisition software. The F180R Attitude and Positioning system uses 2 L1 antennas for position and heading and an Inertial Measurement Unit (IMU) for motion sensing (heave, pitch, roll and yaw). The F180R IMU is mounted directly above the SEA SWATHplus-M transducers on the sidemount. The F180R antennas are mounted at the top of the sidemount offset in a forward/aft configuration. The offsets were applied within the SWATHplus and Coda Octopus F180R acquisition software.

  3. How accurate are the heights or depths?

    Vertical accuracy of the raw data based on system specifications may approximate 1% of water depth, approximately 0.1 to 0.3 meters within the survey area. However, overall vertical accuracies on the order of 50 cm are assumed based on the following considerations: The Coda Octopus F180R Attitude and Positioning system, used to correct for vessel roll, pitch, heave, and yaw, has a theoretical vertical accuracy of a few mm. Real Time Kinematic (RTK) GPS height corrections, broadcast from a continuously operated reference station (CORS) at Central Islip, New York (station NTCI), were used to reference soundings to the North American Vertical Datum of 1988 (NAVD88) and remove water depth variations caused by tides. USGS field tests (unpublished) using submerged targets suggest that the vertical accuracy of the RTK-GPS tidal correction is less than 30cm. Refraction artifacts were minimized by acquiring sound velocity profiles with an ODIM MVP30 moving vessel profiler. However, the ODIM MVP30 failed half-way through the survey. No sound velocity profiles were collected for the remainder of the survey (lines 48 - 109) and refraction corrections were applied during post-processing. Changes in ship draft due to water and fuel usage were not considered.

  4. Where are the gaps in the data? What is missing?

    Line 1 - 51, 61 - 64, 68 - 87, and 93 - 109 were used to generate the bathymetric grid. Lines 52-60, 65 - 67, and 89 - 92 are tie lines collected orthogonal to the shoreline. Tie lines were used to QA/QC the bathymetric data during data processing, but were not incorporated into the final bathymetric grid.

  5. How consistent are the relationships among the observations, including topology?

    This grid represents interpolated data; processed to account for gaps that occurred along-track and between adjacent lines.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: none
These data are NOT to be used for navigation. Mariners should refer to the appropriate nautical chart. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.

  1. Who distributes the data set? (Distributor 1 of 1)

    Jane F. Denny
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, Massachusetts 02543

    508-548-8700 x 2311 (voice)
    508-457-2311 (FAX)

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  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. Is there some other way to get the data?


  6. What hardware or software do I need in order to use the data set?

    These data are available as a ArcInfo 32-bit floating point binary grid in Esri format. The floating point binary grid and associated 'info' folder are stored in one folder 'bathy' that has been compressed using WinZip (ver.14.0) software. To utilize these data, the user must have software capable of uncompressing the zip file and importing and viewing an Esri ArcRaster grid. The zip file also contains associated metadata.

Who wrote the metadata?

Last modified: 17-Oct-2014
Metadata author:
Jane F. Denny
U.S. Geological Survey
394 Woods Hole Road
Woods Hole, Massachusetts 02543

508-548-8700 x 2311 (voice)
508-457-2311 (FAX)

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.8.25 on Fri Oct 17 16:23:46 2014