6-m resolution grid of multibeam bathymetry in western Massachusetts Bay map Quadrangle 2 (Q2_BATHY6M)

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Frequently anticipated questions:

What does this data set describe?

Title:
6-m resolution grid of multibeam bathymetry in western Massachusetts Bay map Quadrangle 2 (Q2_BATHY6M)
Abstract:
The U.S. Geological Survey has conducted geologic mapping to characterize the sea floor offshore of Massachusetts. The mapping was carried out using a Simrad Subsea EM 1000 Multibeam Echo Sounder on the Frederick G. Creed on four cruises conducted between 1994 and 1998. The mapping was conducted in cooperation with the National Oceanic and Atmospheric Administration (NOAA) and with support from the Canadian Hydrographic Service and the University of New Brunswick.
The long-term goal of this mapping effort is to produce high-resolution geologic maps and a Geographic Information System (GIS) project that presents images and grids of bathymetry, shaded relief bathymetry, and backscatter intensity data from these surveys that will serve the needs of research, management and the public.
  1. How might this data set be cited?
    Butman, Bradford, and Danforth, William W., 2007, 6-m resolution grid of multibeam bathymetry in western Massachusetts Bay map Quadrangle 2 (Q2_BATHY6M): Data Series 99, 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, Valentine, Page C., Middleton, Tammie J., and Danforth, William W., 2007, A GIS Library of Multibeam Data for Massachusetts Bay and the Stellwagen Bank National Marine Sanctuary, Offshore of Boston, Massachusetts: Data Series 99, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.883369
    East_Bounding_Coordinate: -70.600019
    North_Bounding_Coordinate: 42.441692
    South_Bounding_Coordinate: 42.322239
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1994
    Ending_Date: 1998
    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 2237 x 3934 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: 41.650000
      Longitude_of_Central_Meridian: -70.316667
      False_Easting: 0.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 6.000000
      Ordinates (y-coordinates) are specified to the nearest 6.000000
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: Mean lower low water
      Depth_Resolution: 0.5
      Depth_Distance_Units: Meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Bradford Butman
    • William W. Danforth
  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
    Oceanographer
    384 Woods Hole Rd
    Woods Hole, MA
    USA

    (508) 548-8700 x2212 (voice)
    (508) 457-2309 (FAX)
    bbutman@usgs.gov
    Hours_of_Service: 8 a.m. - 5 p.m.

Why was the data set created?

This ESRI grid contains multibeam bathymetry data in western Massachusetts Bay map Quadrangle 2 at 6-m resolution.

How was the data set created?

  1. From what previous works were the data drawn?
    Information unavailable from original metadata. (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, Multibeam bathymetric survey data collected by USGS in Massachusetts Bay, 1994-1998.

    Type_of_Source_Media: Information unavailable from original metadata.
    Source_Contribution: Information unavailable from original metadata.
  2. How were the data generated, processed, and modified?
    Date: Unknown (process 1 of 9)
    Data acquisition at sea
    These multibeam data were collected with a Simrad EM1000 multibeam echo sounder mounted on the starboard pontoon of the Canadian Hydrographic Service Vessel Frederick G. Creed. The data were collected over four cruises carried out between the fall of 1994 and fall of 1998. Operation of the Simrad EM1000 was carried out by hydrographers of the Canadian Hydrographic Service. Data were collected along tracklines spaced 5-7 times the water depth apart at a speed of 10-14 knots. The frequency of the sonar was 95kHz. Sound velocity profiles were obtained and input into the Simrad processing system to correct for refraction. Navigation was by means of differential GPS. Person who carried out this activity:
    William Danforth
    U.S. Geological Survey
    Operational Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 x2274 (voice)
    (508) 457-2310 (FAX)
    bdanforth@usgs.gov
    Hours_of_Service: 8 a.m. to 5 p.m. EST
    Date: Unknown (process 2 of 9)
    Data processing and editing at sea
    Processing of the data 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 (<www.omg.unb.ca/~jhc/SwathEd.html>) was used to process, edit, and archive the bathymetric soundings.
    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), sidescan sonar backscatter 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 MassbayMap.sun_315
    3. 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
    4. Map the bathymetric soundings from each processed data file onto a Mercator grid or DTM using weigh_grid with grid nodes spaced at 6 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. Naturally the solution is: weight_depth/weights for each node. For more information, visit the OMG website at <http://www.omg.unb.ca>.
    First a blank binary grid and the weights and weight_depth files must be created:
    Command line: make_blank -float gridFile 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 western Massachusetts Bay Quadrangles 1-3 were created with a grid node spacing of 6 meters, a cutoff radius of 12 meters, and an inner radius to the weighting function of 3 meters:
    Command line: weigh_grid -omg -tide -coeffs -mindep -2 -maxdep -800 -beam_mask -beam_weight -custom_weight EM1000_Weights -butter -power 2 -cutoff 12 -lambda 3 gridFile filename.merged Person who carried out this activity:
    William Danforth
    U.S. Geological Survey
    Operational Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 x2274 (voice)
    (508) 457-2310 (FAX)
    bdanforth@usgs.gov
    Hours_of_Service: 8 a.m. to 5 p.m. EST
    Date: Unknown (process 3 of 9)
    Final data processing and editing
    Processing was carried out to further edit and correct the data and to produce final grids and images of the data. Processing and editing 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. Correct the bathymetric data to mean lower low water by subtracting the observed tide at Boston, Massachusetts from the edited bathymetric soundings. This correction assumes that the tidal phase and amplitude are the same as Boston across the survey area.
    Mean Lower Low Water (MLLW) tidal information was obtained from the NOAA tide server using tide station 8443970 located at Boston, MA (42 degrees 21.3 minutes N, 71 degrees 3.1 minutes W) (http://tidesandcurrents.noaa.gov/). The binary tide file used in the command line below was generated by reformatting the 6 minute tidal information from the NOAA site into a text file that contains Julian Day (DDD) , time (HH MM), and water level height(H.HH) in this format: DDD HH MM SS H.HH. This file was then converted to a binary tide file with:
    Command line: binTide -year YYYY asciiTideFile BinaryTideFile
    The program mergeTide brings the swath soundings to the MLLW vertical tidal datum:
    Command line (tides): mergeTide -tide BinaryTideFile filename.merged Command line (navigation): mergeNav -ahead 5.379 -right 3.851 -below 4.244 filename (prefix only)
    4. Create a 6-m grid of the bathymetric soundings for western Massachusetts Bay Quadrangles using the SwathEd routine weigh_grid.
    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 12 -lambda 3 gridFile filename.merged
    5. 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:
    William Danforth
    U.S. Geological Survey
    Operational Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 x2274 (voice)
    (508) 457-2310 (FAX)
    bdanforth@usgs.gov
    Date: Unknown (process 4 of 9)
    An ESRI bathymetry grid was created by importing data from ASCII grid format into ESRI grid format. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Tammie Middleton
    Operational Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 (voice)
    (508) 457-2310 (FAX)
    Date: Feb-2007 (process 5 of 9)
    Data shifted 1/2 grid cell to northwest (using the ArcMap/Data Management Tools/Projections and Transformations/Raster/Shift tool) to correct for an error identified in the SwathEd gridding algorithm in 2007. Person who carried out this activity:
    William Danforth
    U.S. Geological Survey
    Operational Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 x2274 (voice)
    (508) 457-2310 (FAX)
    bdanforth@usgs.gov
    Data sources produced in this process:
    • q2_bathy6m
    Date: 06-Feb-2017 (process 6 of 9)
    Edits to the metadata were made to fix any errors that MP v 2.9.36 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). Attempted to modify http to https where appropriate. The source information was incomplete and had to be modified to meet the standard. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent. 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: 20-Jul-2018 (process 7 of 9)
    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: 15-Nov-2019 (process 8 of 9)
    Crossref DOI link was added as the first link in the metadata. 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 9 of 9)
    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?
    No attributes are associated with these data.
  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) and tidal offsets, and referenced to mean lower low water. The theoretical vertical resolution of the Simrad EM-1000 multibeam echosounder is 1 % of water depth, approximately 0.3 - 1.0 m within the study area.
  4. Where are the gaps in the data? What is missing?
    These data were corrected for tidal elevation using the NOAA Boston tide gage. This assumes that the tidal elevation and phase are the same as Boston across the survey area. Further processing to correct for the spatial and temporal changes in tidal elevation across the survey area may be undertaken at a later time.
  5. How consistent are the relationships among the observations, including topology?
    Information unavailable from original metadata.

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. 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 (USGS) as the source of this information.
  1. Who distributes the data set? (Distributor 1 of 2)
    Bradford Butman
    U.S. Geological Survey
    Oceanographer
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    (508) 548-8700 x2212 (voice)
    (508) 457-2309 (FAX)
    bbutman@usgs.gov
    Hours_of_Service: 8 a.m. to 5 p.m. EST
  2. What's the catalog number I need to order this data set? Downloadable Data
  3. What legal disclaimers am I supposed to read?
    Although these data have been used by the U.S. Geological Survey (USGS), U.S. Department of the Interior (DOI), no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. 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?
    These data are available in Environmental Systems Research Institute (ESRI) Raster GRID format. The user must have software capable of importing and processing the data file.
  1. Who distributes the data set? (Distributor 2 of 2)
    U.S. Geological Survey Information Services
    Box 25286 Denver Federal Center
    Denver, Colorado
    USA

    (303) 202-4700 (voice)
    (303) 202-4188 (FAX)
    Hours_of_Service: 8 a.m. to 5 p.m. Mountain Time
  2. What's the catalog number I need to order this data set? Downloadable Data
  3. What legal disclaimers am I supposed to read?
    Although these data have been used by the U.S. Geological Survey (USGS), U.S. Department of the Interior (DOI), no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. 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?
    • Availability in digital form:
      Data format: A zip archive containing the ESRI Raster Grid files and metadata. in format AIG (version ArcGIS 9.1) ESRI raster grid Size: 35.182
      Media you can order: DVD-ROM (Density 4.75 Gbytes) (format UDF)
    • Cost to order the data: None

  5. What hardware or software do I need in order to use the data set?
    These data are available in Environmental Systems Research Institute (ESRI) Raster GRID format. The user must have software capable of importing and processing the data file.

Who wrote the metadata?

Dates:
Last modified: 18-Mar-2024
Metadata author:
Bradford Butman
U.S. Geological Survey
Oceanographer
384 Woods Hole Road
Woods Hole, MA
USA

(508) 548-8700 x2212 (voice)
(508) 457-2310 (FAX)
whsc_data_contact@usgs.gov
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is no longer with USGS. (updated on 20240318)
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/data_series/DS-99/q2_bathy6m_meta.faq.html>
Generated by mp version 2.9.51 on Mon Mar 25 16:05:17 2024