Identification_Information:
  Citation:
    Citation_Information:
      Originator: Bradford Butman
      Originator: William W. Danforth
      Publication_Date: 2007
      Title: Q1_BATHY6M - 6-m resolution grid of multibeam bathymetry in western Massachusetts Bay map Quadrangle 1
      Edition: 1.0
      Geospatial_Data_Presentation_Form: raster digital data
      Series_Information:
        Series_Name: Data Series
        Issue_Identification: 99
      Publication_Information:
        Publication_Place: Woods Hole Science Center, Woods Hole, MA
        Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
      Online_Linkage: http://pubs.usgs.gov/ds/99/massbay_gis/2_multibeam/grids/q1_bathy6m.zip
      Online_Linkage: http://pubs.usgs.gov/ds/99/webpages/quad1.html
      Larger_Work_Citation:
        Citation_Information:
          Originator: Butman, Bradford
          Originator: Valentine, Page C.
          Originator: Middleton, Tammie J.
          Originator: Danforth, William W.
          Publication_Date: 2007
          Title: A GIS Library of Multibeam Data for Massachusetts Bay and the Stellwagen Bank National Marine Sanctuary, Offshore of Boston, Massachusetts
          Edition: 1.0
          Series_Information:
            Series_Name: Data Series
            Issue_Identification: 99
          Publication_Information:
            Publication_Place: Woods Hole Science Center, Woods Hole, MA
            Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
          Online_Linkage: http://pubs.usgs.gov/ds/99/
  Description:
    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.
    Purpose: This ESRI grid contains multibeam bathymetry data in western Massachusetts Bay map Quadrangle 1 at 6-m resolution.
  Time_Period_of_Content:
    Time_Period_Information:
      Range_of_Dates/Times:
        Beginning_Date: 1994
        Ending_Date: 1998
    Currentness_Reference: ground condition
  Status:
    Progress: Complete
    Maintenance_and_Update_Frequency: None planned
  Spatial_Domain:
    Bounding_Coordinates:
      West_Bounding_Coordinate: -70.788943
      East_Bounding_Coordinate: -70.600019
      North_Bounding_Coordinate: 42.322239
      South_Bounding_Coordinate: 42.203360
  Keywords:
    Theme:
      Theme_Keyword_Thesaurus: General
      Theme_Keyword: bathymetry
      Theme_Keyword: multibeam
      Theme_Keyword: 6-m grid
      Theme_Keyword: sea floor
      Theme_Keyword: sea floor mapping
      Theme_Keyword: western Massachusetts Bay map Quadrangle 1
      Theme_Keyword: USGS Map I-2731
      Theme_Keyword: Simrad
      Theme_Keyword: EM 1000
      Theme_Keyword: Frederick G. Creed
      Theme_Keyword: Woods Hole Science Center
      Theme_Keyword: WHSC
      Theme_Keyword: Coastal and Marine Geology Program
      Theme_Keyword: CMGP
      Theme_Keyword: U.S. Geological Survey
      Theme_Keyword: USGS
    Theme:
      Theme_Keyword_Thesaurus: ISO 19115 Topic Category
      Theme_Keyword: oceans
      Theme_Keyword: oceans and estuaries
      Theme_Keyword: oceans and coastal
      Theme_Keyword: elevation
      Theme_Keyword: imageryBaseMapsEarthCover
    Place:
      Place_Keyword_Thesaurus: General
      Place_Keyword: Massachusetts Bay
      Place_Keyword: western Massachusetts Bay
      Place_Keyword: Boston
      Place_Keyword: Massachusetts
      Place_Keyword: Stellwagen Basin
      Place_Keyword: MWRA ocean outfall
      Place_Keyword: MWRA
      Place_Keyword: Gulf of Maine
      Place_Keyword: United States
      Place_Keyword: North Atlantic Ocean
  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.
  Point_of_Contact:
    Contact_Information:
      Contact_Organization_Primary:
        Contact_Organization: U.S. Geological Survey
        Contact_Person: Bradford Butman
      Contact_Position: Oceanographer
      Contact_Address:
        Address_Type: mailing and physical address
        Address: 384 Woods Hole Rd
        City: Woods Hole
        State_or_Province: MA
        Postal_Code: 02543-1598
        Country: USA
      Contact_Voice_Telephone: (508) 548-8700 x2212
      Contact_Facsimile_Telephone: (508) 457-2309
      Contact_Electronic_Mail_Address: bbutman@usgs.gov
      Hours_of_Service: 8 a.m. - 5 p.m.
  Native_Data_Set_Environment: Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.1.0.780
Data_Quality_Information:
  Attribute_Accuracy:
    Attribute_Accuracy_Report: No attributes are associated with these data.
  Completeness_Report: 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.
  Positional_Accuracy:
    Horizontal_Positional_Accuracy:
      Horizontal_Positional_Accuracy_Report: These data were navigated with a Differential Global Positioning System (DGPS); they are accurate to +/- 3 meters, horizontally.
    Vertical_Positional_Accuracy:
      Vertical_Positional_Accuracy_Report: 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.
  Lineage:
    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: U.S. Geological Survey
          Publication_Date: Unpublished Material
          Title: Multibeam bathymetric survey data collected by USGS in Massachusetts Bay, 1994-1998
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Range_of_Dates/Times:
            Beginning_Date: 1994
            Ending_Date: 1998
        Source_Currentness_Reference: ground condition
    Process_Step:
      Process_Description:
        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.
      Process_Date: Unknown
      Process_Contact:
        Contact_Information:
          Contact_Person_Primary:
            Contact_Person: William Danforth
            Contact_Organization: U.S. Geological Survey
          Contact_Position: Operational Geologist
          Contact_Address:
            Address_Type: mailing and physical address
            Address: 384 Woods Hole Road
            City: Woods Hole
            State_or_Province: MA
            Postal_Code: 02543-1598
            Country: USA
          Contact_Voice_Telephone: (508) 548-8700 x2274
          Contact_Facsimile_Telephone: (508) 457-2310
          Contact_Electronic_Mail_Address: bdanforth@usgs.gov
          Hours_of_Service: 8 a.m. to 5 p.m. EST
    Process_Step:
      Process_Description:
        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
      Process_Date: Unknown
      Process_Contact:
        Contact_Information:
          Contact_Person_Primary:
            Contact_Person: William Danforth
            Contact_Organization: U.S. Geological Survey
          Contact_Position: Operational Geologist
          Contact_Address:
            Address_Type: mailing and physical address
            Address: 384 Woods Hole Road
            City: Woods Hole
            State_or_Province: MA
            Postal_Code: 02543-1598
            Country: USA
          Contact_Voice_Telephone: (508) 548-8700 x2274
          Contact_Facsimile_Telephone: (508) 457-2310
          Contact_Electronic_Mail_Address: bdanforth@usgs.gov
          Hours_of_Service: 8 a.m. to 5 p.m. EST
    Process_Step:
      Process_Description:
        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.
      Process_Date: Unknown
      Process_Contact:
        Contact_Information:
          Contact_Person_Primary:
            Contact_Person: William Danforth
            Contact_Organization: U.S. Geological Survey
          Contact_Position: Operational Geologist
          Contact_Voice_Telephone: (508) 548-8700 x2274
          Contact_Electronic_Mail_Address: bdanfoth@usgs.gov
    Process_Step:
      Process_Description: An ESRI bathymetry grid was created by importing data from ASCII grid format into ESRI grid format.
      Process_Date: Unknown
      Process_Contact:
        Contact_Information:
          Contact_Organization_Primary:
            Contact_Organization: U.S. Geological Survey
            Contact_Person: Tammie Middleton
          Contact_Position: Operational Geologist
          Contact_Address:
            Address_Type: mailing and physical address
            Address: 384 Woods Hole Road
            City: Woods Hole
            State_or_Province: MA
            Postal_Code: 02543-1598
            Country: USA
          Contact_Voice_Telephone: (508) 548-8700
          Contact_Facsimile_Telephone: (508) 457-2310
    Process_Step:
      Process_Description: 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.
      Process_Date: 200702
      Source_Produced_Citation_Abbreviation: q1_bathy6m
      Process_Contact:
        Contact_Information:
          Contact_Person_Primary:
            Contact_Person: William Danforth
            Contact_Organization: U.S. Geological Survey
          Contact_Position: Operational Geologist
          Contact_Address:
            Address_Type: mailing and physical address
            Address: 384 Woods Hole Road
            City: Woods Hole
            State_or_Province: MA
            Postal_Code: 02543-1598
            Country: USA
          Contact_Voice_Telephone: (508) 548-8700 x2274
          Contact_Facsimile_Telephone: (508) 457-2310
          Contact_Electronic_Mail_Address: bdanforth@usgs.gov
Spatial_Data_Organization_Information:
  Direct_Spatial_Reference_Method: Raster
  Raster_Object_Information:
    Raster_Object_Type: Grid Cell
    Row_Count: 2222
    Column_Count: 2623
    Vertical_Count: 1
Spatial_Reference_Information:
  Horizontal_Coordinate_System_Definition:
    Planar:
      Map_Projection:
        Map_Projection_Name: Mercator
        Mercator:
          Standard_Parallel: 41.650000
          Longitude_of_Central_Meridian: -70.316667
          False_Easting: 0.000000
          False_Northing: 0.000000
      Planar_Coordinate_Information:
        Planar_Coordinate_Encoding_Method: row and column
        Coordinate_Representation:
          Abscissa_Resolution: 6.000000
          Ordinate_Resolution: 6.000000
        Planar_Distance_Units: meters
    Geodetic_Model:
      Horizontal_Datum_Name: North American Datum of 1983
      Ellipsoid_Name: Geodetic Reference System 80
      Semi-major_Axis: 6378137.000000
      Denominator_of_Flattening_Ratio: 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
Distribution_Information:
  Distributor:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Bradford Butman
        Contact_Organization: U.S. Geological Survey
      Contact_Position: Oceanographer
      Contact_Address:
        Address_Type: mailing and physical address
        Address: 384 Woods Hole Road
        City: Woods Hole
        State_or_Province: Massachusetts
        Postal_Code: 02543-1598
        Country: USA
      Contact_Voice_Telephone: (508) 548-8700 x2212
      Contact_Facsimile_Telephone: (508) 457-2309
      Contact_Electronic_Mail_Address: bbutman@usgs.gov
      Hours_of_Service: 8 a.m. to 5 p.m. EST
  Resource_Description: Downloadable Data
  Distribution_Liability:
    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.
  Standard_Order_Process:
    Digital_Form:
      Digital_Transfer_Information:
        Format_Name: ARCG
        Format_Version_Number: 9.1
        Format_Specification: ESRI raster grid
        Format_Information_Content: A zip archive containing the ESRI Raster Grid files and metadata.
        File_Decompression_Technique: zip archive
        Transfer_Size: 26.232
      Digital_Transfer_Option:
        Online_Option:
          Computer_Contact_Information:
            Network_Address:
              Network_Resource_Name: http://pubs.usgs.gov/ds/99/massbay_gis/2_multibeam/grids/q1_bathy6m.zip
          Access_Instructions: Data may be downloaded via the World Wide Web.
        Offline_Option:
          Offline_Media: DVD-ROM
          Recording_Capacity:
            Recording_Density: 4.75
            Recording_Density_Units: Gbytes
          Recording_Format: UDF
    Fees: None
  Technical_Prerequisites: 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.
Distribution_Information:
  Distributor:
    Contact_Information:
      Contact_Organization_Primary:
        Contact_Organization: U.S. Geological Survey Information Services
      Contact_Address:
        Address_Type: mailing address
        Address: Box 25286 Denver Federal Center
        City: Denver
        State_or_Province: Colorado
        Postal_Code: 80225-0046
        Country: USA
      Contact_Voice_Telephone: (303) 202-4700
      Contact_Facsimile_Telephone: (303) 202-4188
      Hours_of_Service: 8 a.m. to 5 p.m. Mountain Time
  Resource_Description: Downloadable Data
  Distribution_Liability:
    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.
  Standard_Order_Process:
    Digital_Form:
      Digital_Transfer_Information:
        Format_Name: ARCG
        Format_Version_Number: 9.1
        Format_Specification: ESRI raster grid
        Format_Information_Content: A zip archive containing the ESRI Raster Grid files and metadata.
        File_Decompression_Technique: zip archive
        Transfer_Size: 26.232
      Digital_Transfer_Option:
        Offline_Option:
          Offline_Media: DVD-ROM
          Recording_Capacity:
            Recording_Density: 4.75
            Recording_Density_Units: Gbytes
          Recording_Format: UDF
    Fees: None
  Technical_Prerequisites: 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.
Metadata_Reference_Information:
  Metadata_Date: 20070327
  Metadata_Contact:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Bradford Butman
        Contact_Organization: U.S. Geological Survey
      Contact_Position: Oceanographer
      Contact_Address:
        Address_Type: mailing and physical address
        Address: 384 Woods Hole Road
        City: Woods Hole
        State_or_Province: MA
        Postal_Code: 02543-1598
        Country: USA
      Contact_Voice_Telephone: (508) 548-8700 x2212
      Contact_Facsimile_Telephone: (508) 457-2310
      Contact_Electronic_Mail_Address: bbutman@usgs.gov
  Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
  Metadata_Standard_Version: FGDC-STD-001-1998
  Metadata_Time_Convention: local time
  Metadata_Access_Constraints: None
  Metadata_Use_Constraints: None
  Metadata_Extensions:
    Online_Linkage: http://www.esri.com/metadata/esriprof80.html
    Profile_Name: ESRI Metadata Profile
