2-meter bathymetric data collected in 2016 by the U.S. Geological Survey off Town Neck Beach in Sandwich, Massachusetts, during field activity 2016-017-FA (GeoTIFF image)

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Frequently anticipated questions:

What does this data set describe?

2-meter bathymetric data collected in 2016 by the U.S. Geological Survey off Town Neck Beach in Sandwich, Massachusetts, during field activity 2016-017-FA (GeoTIFF image)
Geophysical and geological survey data were collected off Town Neck Beach in Sandwich, Massachusetts, in May and July 2016. Approximately 130 linear kilometers of subbottom (seismic-reflection) and 234-kilohertz interferometric sonar (bathymetric and backscatter) data were collected along with sediment samples, sea floor photographs, and (or) video at 26 sites within the geophysical survey area. Sediment grab samples were collected at 19 of the 26 sampling sites and video and (or) photographic imagery of the sea floor were taken at all 26 sites. These survey data are used to characterize the sea floor by identifying sediment-texture, seabed morphology, and underlying geologic structure and stratigraphy. Data collected during these 2016 surveys are included in this data release: https://doi.org/10.5066/P9HZHXXV.
More information can be found on the websites for the Woods Hole Coastal and Marine Science Center field activities at https://cmgds.marine.usgs.gov/fan_info.php?fan=2016-017-FA and https://cmgds.marine.usgs.gov/fan_info.php?fan=2016-037-FA.
More information can be found on the WHCMSC Field Activity webpage: https://cmgds.marine.usgs.gov/fan_info.php?fan=2016-017-FA. Data collected during the 2016 survey can be obtained here: https://doi.org/10.5066/P9HZHXXV.
  1. How might this data set be cited?
    U.S. Geological Survey, 2019, 2-meter bathymetric data collected in 2016 by the U.S. Geological Survey off Town Neck Beach in Sandwich, Massachusetts, during field activity 2016-017-FA (GeoTIFF image): data release DOI:10.5066/P9HZHXXV, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts.

    Online Links:

    This is part of the following larger work.

    Ackerman, Seth D., Foster, David S., Danforth, William W., and Huntley, Emily C., 2019, High-resolution geophysical and sampling data collected off Town Neck Beach in Sandwich, Massachusetts, 2016: data release DOI:10.5066/P9HZHXXV, U.S. Geological Survey, Reston, VA.

    Online Links:

    Suggested citation: Ackerman S.D., Foster D.S., Danforth W.W., and Huntley, E.C., 2019, High-resolution geophysical and sampling data collected off Town Neck Beach in Sandwich, Massachusetts, 2016: U.S. Geological Survey data release, https://doi.org/10.5066/P9HZHXXV.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.515463
    East_Bounding_Coordinate: -70.440835
    North_Bounding_Coordinate: 41.789678
    South_Bounding_Coordinate: 41.758149
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5c926dc0e4b0938824573d57/?name=2016-017-FA_Bathymetry2m_NAVD88_browse.jpg (JPEG)
    Depth-colored hillshade image of bathymetry from off Town Neck Beach in Sandwich, MA
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 17-May-2016
    Ending_Date: 23-May-2016
    Ground condition of survey dates: 20160517-20160523. No geophysical data were collected on May 18 (JD 139), 21 (JD 142), and 22 (JD 143), 2016 ; see Completeness_Report for more information.
  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 1698 x 3073, type Pixel
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 19N
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -69
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000
      False_Northing: 0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 2.0
      Ordinates (y-coordinates) are specified to the nearest 2.0
      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: 0.001
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    There are no attributes associated with a GeoTIFF, however, the pixel values of the 32-bit bathymetry image (2016-017-FA_Bathymetry2m_NAVD88.tif) are depth values. Although the GeoTIFF images has a rectangular extent, areas outside the survey area have a no data value of "NoData" that should be recognized when using the image in GIS software. Data values represent depth in meters referenced to 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)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Seth Ackerman
    U.S. Geological Survey
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 x2315 (voice)
    508-457-2310 (FAX)

Why was the data set created?

This gridded bathymetry image represents approximately 3.7 square kilometers of interferometric sonar (Systems Engineering and Assessment Ltd. SWATHplus-M, now Bathyswath) data collected by the U.S. Geological Survey off Town Neck Beach in Sandwich, Massachusetts, in May 2016 during USGS field activity 2016-017-FA. These data can be used in conjunction with other geophysical and sample data to identify sea-floor morphology and sediment texture.

How was the data set created?

  1. From what previous works were the data drawn?
    raw data (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, raw SWATHplus-M data.

    Type_of_Source_Media: disc
    USGS Field Activity 2016-017-FA: A 234-kHz Systems Engineering and Assessment Ltd. (SEA) SWATHplus-M (now Bathyswath) interferometric sonar was mounted on a rigid pole on the bow of the R/V Rafael. Data were acquired during May 2016.
    Survey: Survey lines were run at an average speed of 5 knots and were generally spaced 30 m apart to obtain overlapping swaths of data and full SEABed coverage.
    Sonar: The SEA SWATHplus-M operates at a frequency of 234-kHz and a variable range (increased or decreased manually depending on water depth). The system was operated with a 60-percent transmit power, a 34-cycle transmit pulse length, 4096 samples per channel, and a ping range of 46 meters.
    Speed of Sound: Sound-velocity profiles were collected several times each survey day with a hand-casted AML Minos X SVPT (Applied Microsystems) sound velocimeter.
    Tides: Tides were originally corrected during post-processing to Mean Sea Level using a NOAA-generated zone tidal model (stellwagen_tides.zdf) and the nearest NOAA-observed tide dataset (Boston_MSL_8443970_June2016.tid) that included all the survey dates. The final bathymetry surface was transformed to the NAVD88 reference surface using VDatum (version 3.9).
  2. How were the data generated, processed, and modified?
    Date: 2016 (process 1 of 8)
    Processing Step 1. Raw to processed conversion for USGS field activity 2016-017-FA: Each raw SWATHplus bathymetric sonar file (SXR) was converted to a SWATHplus processed file (SXP) using SEA SWATHplus Swath Processor (ver. During the conversion process, sound velocity profiles were used to minimize potential refraction artifacts from fluctuations in the speed of sound within the water column. Various bathymetric filters were applied to eliminate sounding outliers. Predicted tidal information was merged into the processed file (SXP) during this conversion, however final tidal corrections were applied later in the processing flow. Bathymetric filtering typically included low amplitude (100%), range (0-4 m), box (3-50 m depth, 1.5-75 m horizontal), median (window size of 5), alongtrack 1 (depth difference of 5 m, window size of 5 m, and learn rate of 0.7), alongtrack 2 (depth difference of 1.5 m, window size of 1 m, and learn rate of 0.9), and mean filters (0.25 m). These represent the typical parameters used for the majority of the survey but slight adjustments were required for some areas. This process step and all subsequent process steps were performed by the same person - Seth Ackerman. Person who carried out this activity:
    Seth Ackerman
    U.S. Geological Survey
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 x2315 (voice)
    508-457-2310 (FAX)
    Date: 2018 (process 2 of 8)
    Processing Step 2. CARIS preliminary processing for USGS field activity 2016-017-FA: A new CARIS HIPS project (ver. 10.1) was created for this field activity with projection information set to Universal Transverse Mercator (UTM) Zone 19N, WGS 84. Each SWATHplus processed file (SXP) was imported to the new CARIS project using the Import/Conversion Wizard. Delayed heave from raw POS MV files was used to update HIPS survey lines using the import auxiliary data function. Navigation was reviewed and edited as needed using the navigation editor tool. Data were merged selecting no tide and the delayed heave source. A 2-m resolution Swath Angle Weighted (SWATH) surface was created to incorporate survey lines as they were processed, and the SWATH surfaces were reviewed for inconsistencies and anomalies. Beam-to-beam slopes and across track angle filters were applied to the soundings line by line and then further edited manually as needed. The refraction editor was used to adjust sound speed values in areas where velocimeter data did not adequately correct depth profiles obviously influenced by local anomalies in speed of sound through the water column. Survey lines were remerged and the surface was recalculated to incorporate processing edits. Preliminary processing was done during the survey and additional processing was done post-survey with CARIS HIPS and SIPS version 10.1. This process step was done between 2016 and 2018.
    Date: 2018 (process 3 of 8)
    Processing Step 3. Prepare and apply POS MV and Zone Tidal Model data for USGS field activity 2016-017-FA: Post-processed navigation and vessel attitude data from POSPac SBET files were used to update HIPS survey lines using the import auxiliary data function in CARIS (version 10.3). Navigation source was set to Applanix SBET, and navigation was re-reviewed and edited as needed using the Navigation Editor tool. Tide data referenced to Mean Sea Level (MSL) were applied using the NOAA Zone Tidal Model (stellwagen_tides.zdf) and observed tide data from the nearest tidal station (Boston_MSL_8443970_June2016.tid). All survey lines were remerged selecting the Zone Tidal Model tides and delayed heave sources.
    Date: Oct-2018 (process 4 of 8)
    Processing Step 4. Final CARIS bathymetry surface creation and export: A final 2-m resolution SWATH surface was created using the Swath Angle method with a maximum footprint of 5. Then, small "no data" holidays were filled using the "Fill Raster Holiday" tool and a 5x5 cell filter using data from a minimum of 5 neighboring cells. The CARIS SWATH surface was exported as a 2-m resolution ASCII file referenced to UTM Zone 19N, WGS 84 and MSL tidal heights. Data sources produced in this process:
    • 2m_SWATH_MSL_v1.asc
    Date: Oct-2018 (process 5 of 8)
    Processing Step 5. Transform surface to NAVD88: The NOAA's Vertical Datum Transformation tool (VDatum v. 3.9) was used to transform the CARIS bathymetry surface (MSL) to the North American Vertical Datum of 1988 (NAVD 88). Data sources produced in this process:
    • 2m_SWATH_MSL_v1_NAVD88.asc
    Date: 2018 (process 6 of 8)
    Processing Step 6. Convert NAVD88 ASCII to GeoTIFF: Global Mapper (version 18) was used to convert the ASC surface created from the VDatum software to a 32-bit GeoTIFF image representing the final bathymetry surface referenced to the NAVD 88 heights. Data sources produced in this process:
    • 2016-017-FA_Bathymetry2m_NAVD88_GeoTIFF.tif
    Date: Jun-2019 (process 7 of 8)
    Processing Step 7. Sound velocity profile (SVP) data were bundled with this bathymetry dataset to archive the sonuds speed dataset. The SVP data can be found in a zip file (2016-017-FA_SVP.zip) that contains 13 SVP profiles in text format. Each SVP text file has a header line with the following format: SoundVelocity (file type), 1.00 (file format version number), cast number (XX), date/time of file creation ( YYYYMMDDhhmm), latitude (decimal degrees), longitude (decimal degrees), radii around the lat/long position for which the profile is valid (set to 1 meter), date of profile start ( YYYYMMDDhhmm), date of profile stop ( YYYYMMDDhhmm), source instrument of the profile (MVP P, where P stands for Probe), number of values in the profile. After the header line, there are 2 columns of data separated by a space. The first column is depth (in meters) and the second column is speed of sound (in meters per second). Data sources produced in this process:
    • 2016-017-FA_SVP.zip
    Date: 07-Aug-2020 (process 8 of 8)
    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)
  3. What similar or related data should the user be aware of?

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?
    USGS Field Activity 2016-017-FA: Navigation for the SWATHplus-M system was acquired using the WGS 84 coordinate system with an Applanix POS MV Wavemaster (model 220, V5), which blends Global Navigation Satellite Systems (GNSS) with acceleration data from a Inertial Measurement Unit (IMU) and GPS azimuthal heading. The POS MV was configured with two AeroAntenna Technologies GPS antennas located at either end of a 2-m baseline, which was oriented fore and aft and mounted atop the rigid pole on which the SWATHplus-M transducers were mounted at the bow of the R/V Rafael. DGPS positions were obtained from the primary antenna located on the forward end of the baseline, and the positional offsets between the antenna and the navigational reference point (the POS MV IMU) were accounted for in the Applanix POSView (version 8.60) acquisition software. DGPS positions are horizontally accurate to 0.5-2 meters, but accuracy can increase to less than 10 cm after post-processing with Applanix POSPac (version 8.1).
    Positional offsets were applied within the SWATHplus acquisition software (version and stored within the SXR format data.
    Note that post-processed horizontal navigation data from the Applanix POS MV were applied during the bathymetry processing in CARIS software at a later date; see process step 3.
  3. How accurate are the heights or depths?
    USGS Field Activity 2016-017-FA: Vertical accuracy of the raw data based on system specifications may approximate 1% of water depth. In the Town Neck Beach survey area, 1% of the water depth (1-18 meters) translates to a vertical accuracy range of 1-18 centimeters. However, overall vertical accuracies on the order of 50 cm or better are assumed based on the following considerations: the Applanix POS MV Wavemaster, used to correct for vessel roll, pitch, heave, and yaw, has a theoretical vertical accuracy of a few mm; and tidal offsets were corrected using a NOAA-generated zone tidal model, which introduces some error into the depth measurements.
    USGS field tests (unpublished) using submerged targets suggest that the vertical accuracy of the RTK-GPS tidal correction is better than 30cm. Refraction artifacts were minimized by acquiring a range of sound velocity profiles with a hand-casted AML Minos X SVPT (Applied Microsystems) sound velocimeter (for the duration of survey 2016-017-FA). Sound velocity data were entered into the SWATHplus acquisition software to model the sound velocity structure of the water column. Changes in ship draft due to water and fuel usage were not considered.
  4. Where are the gaps in the data? What is missing?
    Nearly all survey line bathymetric data (generally surveyed parallel to the coastline) collected within the survey area were incorporated in this bathymetric surface.
    Tielines and transit lines were typically excluded from this bathymetric surface, especially if equal or higher quality survey line data were available. Any tieline and transit line data would be used to verify tide corrections during post-processing. Data from the patch test lines were imported but not processed and are therefore excluded from this dataset.
    Time gaps occur when no data were collected on 20160518, 20160521, and 20160522 (May 18 (JD 139), 21 (JD 142), and 22 (JD 143), 2016) due to weather conditions, rough seas and equipment maintenance and (or) failure.
  5. How consistent are the relationships among the observations, including topology?
    This bathymetric surface represents interpolated data at 2-meter resolution. Bathymetric data were processed to account for gaps that occurred along-track and between adjacent lines. Quality control and data processing were conducted to remove spurious points and minimize refraction artifacts. Soundings from the survey were processed and edited using Computer Aided Resource Information System (CARIS) Hydrographic Information Processing System (HIPS; versions 10.1 and 10.3). Although the soundings were edited, small data spikes may still exist. While much effort was devoted to cleaning the data and minimizing survey artifacts, some artifacts may still be seen in the final gridded bathymetric surface 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.

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)
    U.S. Geological Survey-ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? USGS data release 2016-017-FA bathymetry from offshore of Town Neck Beach in Sandwich, Massachusetts, collected in May 2016. This dataset contains the 32-bit floating point GeoTIFF image (2016-017-FA_Bathymetry2m_NAVD88.tif) with a world file (2016-017-FA_Bathymetry2m_NAVD88.tfw), browse graphic (2016-017-FA_Bathymetry2m_NAVD88_browse.jpg), sound velocity profile data (2016-017-FA_SVP.zip) and metadata file (2016-017-FA_Bathymetry2m_NAVD88_meta.xml). The pixel values of the 32-bit floating point GeoTIFF image are depth values.
  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?
    This dataset contains a 32-bit floating point GeoTIFF image with a world file and associated metadata. To utilize these data, an image processing or GIS software package capable of viewing a 32-bit floating point GeoTIFF image is needed. Standard image viewing software cannot translate a 32-bit floating point GeoTIFF image.

Who wrote the metadata?

Last modified: 07-Aug-2020
Metadata author:
Seth Ackerman
U.S. Geological Survey
384 Woods Hole Rd.
Woods Hole, MA

508-548-8700 x2315 (voice)
508-457-2310 (FAX)
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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