1-meter backscatter imagery collected in 2013 by the U.S. Geological Survey south of Martha's Vineyard and north of Nantucket, Massachusetts (2013-003-FA_Backscatter_1m.tif, 8-bit GeoTIFF, UTM Zone 19N, WGS 84)

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Frequently anticipated questions:


What does this data set describe?

Title:
1-meter backscatter imagery collected in 2013 by the U.S. Geological Survey south of Martha's Vineyard and north of Nantucket, Massachusetts (2013-003-FA_Backscatter_1m.tif, 8-bit GeoTIFF, UTM Zone 19N, WGS 84)
Abstract:
These data were collected under a cooperative agreement between the Massachusetts Office of Coastal Zone Management (CZM) and the U.S. Geological Survey (USGS), Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center (WHCMSC). Initiated in 2003, the primary objective of this program is to develop regional geologic framework information for the management of coastal and marine resources. Accurate data and maps of sea floor geology are important first steps toward protecting fish habitat, delineating marine resources, and assessing environmental changes due to natural or human impacts. The project is focused on the inshore waters of coastal Massachusetts, primarily in water depths of 5 to 30 meters (m) deep. Data collected for the mapping cooperative have been released in a series of USGS Open-File Reports (http://woodshole.er.usgs.gov/project-pages/coastal_mass/). The geophysical data were collected during a survey in 2013 during USGS Field Activity 2013-003-FA (http://cmgds.marine.usgs.gov/fan_info.php?fa=2013-003-FA) and cover approximately 185 square kilometers of the inner continental shelf.
  1. How might this data set be cited?
    U.S. Geological Survey, 2016, 1-meter backscatter imagery collected in 2013 by the U.S. Geological Survey south of Martha's Vineyard and north of Nantucket, Massachusetts (2013-003-FA_Backscatter_1m.tif, 8-bit GeoTIFF, UTM Zone 19N, WGS 84): Open-File Report 2016-1168, 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.

    Ackerman, Seth D., Brothers, Laura L., Foster, David S., Andrews, Brian D., Baldwin, Wayne E., and Schwab, William C., 2016, High-Resolution Geophysical Data From the Inner Continental Shelf: South of Martha's Vineyard and North of Nantucket, Massachusetts: Open-File Report 2016-1168, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.810609
    East_Bounding_Coordinate: -70.029975
    North_Bounding_Coordinate: 41.390816
    South_Bounding_Coordinate: 41.192901
  3. What does it look like?
    http://pubs.usgs.gov/of/2016/1168/GIS_catalog/browse_img/big/2013-003-FA_Backscatter1m.jpg (JPEG)
    Gray-scale image of interferometric backscatter
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 22-May-2013
    Ending_Date: 11-Jun-2013
    Currentness_Reference:
    ground condition of survey dates: 20130522-20130611; 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 20981 x 68808, 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: 19
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -69.000000
      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 1.000000
      Ordinates (y-coordinates) are specified to the nearest 1.000000
      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.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    There are no attributes associated with a GeoTIFF image. Pixel values for the GeoTIFF have a possible 8-bit pixel range of 0 to 255. However, the acoustic reflectivity data range from 1 to 188, with the NO DATA value at 189 (pixel values 190 to 255 fall outside the range of the data values). Low-backscatter intensity is represented by dark tones (low values) and high-backscatter intensity is represented by bright tones (high values). When using this image in GIS software such as ArcGIS, use the symbology "ColorMap" and the background color of 189 can be set to transparent or null to remove "white space" and none of the real data values will be affected.
    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 imagery layer represents approximately 185 square kilometers of interferometric sonar (Systems Engineering and Assessment Ltd. SWATHPlus-M) backscatter data collected by the U.S. Geological Survey during USGS survey 2013-003-FA in 2013 offshore of Massachusetts, south of Martha's Vineyard and north of Nantucket. 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 bathymetry data.

    Type_of_Source_Media: disc
    Source_Contribution:
    USGS Field Activity 2013-003-FA: A 234 kHz Systems Engineering and Assessment Ltd. (SEA) SWATHplus interferometric sonar was mounted on the port side of the M/V Scarlett Isabella. Data were acquired during May and June 2013. USGS Configuration: Survey: Survey lines were run at an average speed of 5 knots and were generally spaced 100 m apart to obtain overlapping swaths of data and full sea-floor 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 transmit power: 80 percent, a transmit length: 43 cycles, 4096 samples per channel, ping rate of 15 per second. Additional sonar configuration information that are not necessarily applicable to the backscatter imagery can be found in the metadata for the bathymetry surface included with this report (USGS Open-File Report 2016-XXXX, High-Resolution Geophysical Data From the Inner Continental Shelf: South of Martha's Vineyard and North of Nantucket, Massachusetts. at http://pubs.usgs.gov/of/2016/1168/ofr2016-1168-data_catalog.html). Small cross-track gaps occur probably as a result of the ship pitching in rough seas. These gaps were not filled or interpolated.
  2. How were the data generated, processed, and modified?
    Date: 2015 (process 1 of 6)
    1. SonarWiz import and processing for USGS field activity 2013-003-FA: Each raw SWATHPlus sonar file (sxr) imported (channels 1 and 2) into SonarWiz software (version 5.06.0018) on the M/V Scarlet Isabella for preliminary shipboard processing. Three separate SonarWiz projects were created (MV_South, NoMansLand, and Nantucket) for the different parts of the survey area. Each line received a bottom tracking correction to remove the water column at nadir. SonarWiz has an automatic bottom-tracking algorithm that generally performs well in most coastal settings. Auto tracking parameters for this survey were set to a blanking value of 7; a duration value of 2; and a threshold of 93 with line smoothing turned on. Some lines required further adjustment to the auto bottom tracking delineation (slightly adjusting the values listed previously), and for nearly all lines some manual editing of the altitude was required in SonarWiz Bottom Tracker. There was a 0.5 m additional altitude offset applied to the bottom tracking, in order to minimize nadir beam pattern noise nearest to nadir in the mosaic. The only gain function applied in SonarWiz during shipboard processing 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. Additional line by line editing, including bottom track adjustments and EGN recalculation were done in post-processing following the survey using SonarWiz (versions 5.06.0018, 5.07.0009, 5.08.0001, 6.0.1.0018, 6.0.1.0027, and 6.0.1.0032). This process step was done between 2013 and 2015. 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
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA
    USA

    508-548-8700 x2315 (voice)
    508-457-2310 (FAX)
    sackerman@usgs.gov
    Date: 2015 (process 2 of 6)
    2. SonarWiz export for USGS field activity 2013-003-FA: Backscatter imagery for each of the SonarWiz projects was exported as 8-bit GeoTIFF images (UTM Zone 19N, WGS 84) at 1-m resolution. This created a GeoTIFF image and world file (tfw) for each sub-area of the survey. High backscatter intensity values are shown by light tones and low backscatter intensity values are shown by dark tones in the imagery.
    Date: 2016 (process 3 of 6)
    3. Combine backscatter imagery for USGS field activity 2013-003-FA: The three GeoTIFFs created in the previous process step were opened in Global Mapper (version 17.0). The images were combined into a single GeoTIFF image and exported as a composite 1-meter GeoTIFF backscatter image (using Export, Export Raster/Image Format..., GeoTIFF; all of the default Global Mapper export values were used, including Generate TFW (World) File; the compression format of the TIFF is Packbits). Data sources produced in this process:
    • 2013-003-FA_Backscatter1m.tif
    Date: 20-Jul-2018 (process 4 of 6)
    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: 30-Jan-2019 (process 5 of 6)
    Fixed a broken link and added the DOI link as first link. 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: 08-Sep-2020 (process 6 of 6)
    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 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 bright tones (high values). The range of values is limited to 0-188. The nodata value is 189.
  2. How accurate are the geographic locations?
    USGS Field Activity 2013-003-FA: Navigation was acquired with a Coda Octopus F185R Real-time Kinematic Global Positioning System (RTK-GPS); which is accurate to less than 1 meter (typically on the order of centimeters) horizontally. The SWATHPlus-M transducers were mounted on a rigid pole, approximately 2.17 m below the water line, along the port side of the M/V Scarlett Isabella. The RTK-GPS antenna was located on the same pole approximately 4.6 m above the sea surface. These offsets were corrected within the SWATHPlus acquisition software.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Nearly all quality main survey line backscatter data (generally shore parallel) that were collected within the survey area south of Martha's Vineyard and north of Nantucket were incorporated in this backscatter image. Backscatter from tielines and transit lines were not processed and are therefore excluded from this image. On several days during the survey (May 27-June 1) the vessel experienced considerable heave in rough sea, especially heading in the western direction in the area south of Martha's Vineyard. Survey lines L31, L33, L35, L53, L59, L63, L68-84 and L101 exhibit a number of across-track "data dropouts." These gaps were not filled or interpolated. Time gaps occurred during this field activity where no surveying was done due to bad weather, rough seas and stops in port for crew changes. Planned surveying was paused and no main survey line data were collected during these times:
    JD143 15:20 - JD146 20:06 (no data were collected on JD144 or JD145)
    JD149 15:40 - JD151 18:59 (no data were collected on JD150)
    JD153 00:01 - JD153 14:32
    JD155 18:16 - JD156 02:06
    JD158 06:12 - JD160 19:15 (no data were collected on JD159)
    
  5. How consistent are the relationships among the observations, including topology?
    This GeoTIFF represents interferometric backscatter imagery collected along main survey lines at 1-meter per pixel resolution. Sonar data were nominally collected at 100-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:
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)
    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
  2. What's the catalog number I need to order this data set? USGS data release 2013-003-FA backscatter imagery from south of Martha's Vineyard and north of Nantucket (2013-003-FA_Backscatter.zip). The zip file contains a folder with the an 8-bit GeoTIFF image (2013-003-FA_Backscatter1m.tif) with a world file (2013-003-FA_Backscatter1m.tfw). Metadata files in three standard formats are also included in the zip file.
  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 ZIP file contains an 8-bit GeoTIFF image compressed using the Packbits compression format with a world file. To utilize these data an image processing or GIS software package capable of viewing an 8-bit GeoTIFF image with Packbits compression.

Who wrote the metadata?

Dates:
Last modified: 08-Sep-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/open_file_report/ofr2016-1168/2013-003-FA_Backscatter1m_meta.faq.html>
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