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

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Frequently anticipated questions:

What does this data set describe?

Title:
Backscatter imagery collected in 2016 by the U.S. Geological Survey off Town Neck Beach Sandwich, Massachusetts, during field activity 2016-017-FA (GeoTIFF image)
Abstract:
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.
Supplemental_Information:
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, Backscatter imagery collected in 2016 by the U.S. Geological Survey off Town Neck Beach 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:

    Other_Citation_Details:
    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: -70.495891
    East_Bounding_Coordinate: -70.450406
    North_Bounding_Coordinate: 41.791132
    South_Bounding_Coordinate: 41.756820
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5c926dc4e4b0938824573d5b/?name=2016-017-FA_Backscatter_browse.jpg (JPEG)
    Gray-scale image of interferometric backscatter collected 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
    Currentness_Reference:
    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 23553 x 23366, type Pixel
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 19N
      Transverse_Mercator:
      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 0.16
      Ordinates (y-coordinates) are specified to the nearest 0.16
      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:
    Image pixel values contain acoustic backscatter intensity values normalized to an 8-bit range (0 – 255). The NoData value is set to 0 (zero) for the areas where no data were collected. Low-backscatter intensity is represented by dark tones (low values) and high-backscatter intensity is represented by light tones (high values).
    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
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA
    USA

    508-548-8700 x2315 (voice)
    508-457-2310 (FAX)
    sackerman@usgs.gov

Why was the data set created?

This backscatter image represents approximately 3.7 square kilometers of interferometric sonar (Systems Engineering and Assessment Ltd. SWATHplus-M, now Bathyswath) backscatter 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
    Source_Contribution:
    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.
    Configuration:
    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.
    Additional system configuration information that is not necessarily applicable to the backscatter imagery can be found in the metadata for the bathymetry included with this data release (https://doi.org/10.5066/P9HZHXXV).
  2. How were the data generated, processed, and modified?
    Date: Aug-2016 (process 1 of 4)
    1. Each raw SWATHplus sonar file (SXR format) was imported (channels 1 and 2) into Chesapeake Technologies Inc. SonarWiz software (version 6.01.0032). SonarWiz has an automatic bottom-tracking algorithm (i.e. slant-range correction) that generally performs well in most coastal settings and effectively removes the water column from each sonar file. For some lines, additional manual editing of the altitude was required in the SonarWiz Bottom Tracker. The only gain function applied in SonarWiz was an empirical gain normalization function (EGN). The Overlap Mode in the SonarWiz project was set to average, which blends the backscatter data in the far range of a line with the overlapping data from the adjacent line, producing a final backscatter mosaic. Person who carried out this activity:
    Seth Ackerman
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA
    USA

    508-548-8700 x2315 (voice)
    508-457-2310 (FAX)
    sackerman@usgs.gov
    Date: Apr-2018 (process 2 of 4)
    2. The backscatter imagery generated in the previous process step exhibited a processing anomaly at nadir (directly below the sonar) as a result of the bottom-tracking algoritm (slant-range correction) that was not properly removing the water column in the earlier version of SonarWiz software. Using a newer version of SonarWiz (version 7.02.05), the slant-range correction and EGN were reapplied and a new backscatter image was created for the Town Neck Beach survey area. The backscatter image was exported as a 32-bit GeoTIFF image (UTM Zone 19N, WGS 84) at 16-cm resolution. This created a GeoTIFF image and world file (tfw) of the survey area. High backscatter intensity values are shown by light tones and low backscatter intensity values are shown by dark tones in the imagery. Person who carried out this activity:
    William W. Danforth
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA
    USA

    508-548-8700 x2274 (voice)
    508-457-2310 (FAX)
    bdanforth@usgs.gov
    Date: Jun-2018 (process 3 of 4)
    3. The backscatter GeoTIFF from the SonarWiz software has a NoData value of 0 but also has another NoData value of -32767. The valid backscatter values were normalized in SonarWiz to a range from 0 - 250, where 0 is the NoData. Using gdal_calc.py (installed with Python 3.6 -- /Library/Frameworks/Python.framework/Versions/3.6/bin/gdal_calc.py) the NoData value was set to simply 0 using the following code: gdal_calc.py -A 2016-017-FA_Backscatter_TEMP.tif --outfile=2016-017-FA_Backscatter.tif --calc="A*(A>0)" --NoDataValue=0 Person who carried out this activity:
    Seth Ackerman
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA
    USA

    508-548-8700 x2315 (voice)
    508-457-2310 (FAX)
    sackerman@usgs.gov
    Date: 07-Aug-2020 (process 4 of 4)
    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?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    Image pixel values contain gray-scale acoustic reflectivity values normalized to an 8-bit data range (0-255). Low backscatter is represented by dark tones (low values) and high backscatter is represented by light tones (high values). The NoData value is set to 0.
  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. Note that although the final backacatter image has a pixel resolution of 16-cm, the horizontally accuracy of the DGPS positions are 0.5-2 meters.
    Positional offsets were applied within the SWATHplus acquisition software (version 3.07.17.00) and stored within the SXR format data.
    Note: During bathymetric processing, using Teledyne CARIS hydrographic software, the Applanix POS MV post-processed navigation data were applied to the bathymetric data, increasing navigational accuracies of the bathymetric data. However, during backscatter processing, using Chesapeake Technologies SonarWiz, the DGPS position data stored in the SXR headers were used, yielding horizontal accuracies of 0.5 – 2 m.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Backscatter data, along tracklines generally oriented parallel to the beach, were incorporated in this backscatter image. Backscatter data collected during the bathymetric patch test, along the transit lines in and out of the Sandwich Marina and along tielines (1-4) were not incorporated in this image.
    Data from some survey lines have been omitted where they overlapped with equal or better quality data from adjacent lines. Small cross-track gaps can occur as a result of the ship pitching and rolling; between-track gaps can occur where overlapping swaths were not achieved. Very few of these types of gaps occurred in this dataset.
    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 GeoTIFF represents interferometric backscatter imagery collected along main survey lines at 16-centimeter resolution. Sonar data were nominally collected at 30-meter trackline spacing to ensure nearly 100 percent coverage of the survey area. Gaps may occur along-track and between adjacent lines, especially where the ship had to maneuver to avoid obstacles during surveying.

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:
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
    USA

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? USGS data release 2016-017-FA backscatter imagery collected off Town Neck Beach. This dataset contains a 32-bit GeoTIFF image (2016-017-FA_Backscatter.tif) with a world file (2016-017-FA_Backscatter.tfw), browse graphic (2016-017-FA_Backscatter_browse.jpg) and metadata file (2016-017-FA_Backscatter_meta.xml).
  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 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 GeoTIFF image is needed.

Who wrote the metadata?

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

508-548-8700 x2315 (voice)
508-457-2310 (FAX)
sackerman@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_P9HZHXXV/2016-017-FA_Backscatter_meta.faq.html>
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