5-meter bathymetric data collected in 2013 by the U.S. Geological Survey south of Martha's Vineyard and north of Nantucket, Massachusetts (32-bit floating-point bathymetry GeoTIFF and depth-colored hillshaded GeoTIFF, UTM Zone 19N, WGS 84)

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Frequently anticipated questions:


What does this data set describe?

Title:
5-meter bathymetric data collected in 2013 by the U.S. Geological Survey south of Martha's Vineyard and north of Nantucket, Massachusetts (32-bit floating-point bathymetry GeoTIFF and depth-colored hillshaded 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, 5-meter bathymetric data collected in 2013 by the U.S. Geological Survey south of Martha's Vineyard and north of Nantucket, Massachusetts (32-bit floating-point bathymetry GeoTIFF and depth-colored hillshaded 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_Bath5m.jpg (JPEG)
    Depth-colored hillshade image of bathymetry
  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 4183 x 13008, 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 5.000000
      Ordinates (y-coordinates) are specified to the nearest 5.000000
      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.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: Mean lower low water
      Depth_Resolution: 0.1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    There are no attributes associated with a GeoTIFF however the pixel values of the 32-bit image are depth values. The "no data" value is set to 3.402823e+038. Data values represent depth in meters referenced to mean lower low water (MLLW). The color-ramp of the hillshade bathymetry image is full visual spectrum from red to purple representing shallow (less than 10 meters) to deep (approximately 30 meters), respectively. The "no data" value in the hillshaded image is RGB value: 0,0,0.
    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?

These data are used to define sea-floor morphology as part of the Massachusetts Seafloor Mapping Project. This gridded bathymetry layer and depth-colored hillshaded image represents approximately 185 square kilometers of interferometric sonar (Systems Engineering and Assessment Ltd. SWATHPlus-M) bathymetry 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. An additional approximately 50 square kilometers of interferometric bathymetry data was collected north of Nantucket during the same survey.

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. Speed of Sound: Sound-velocity profiles were collected approximately every 2 hours using an ODIM MVP30 moving vessel profiler or a hand-casted AML Oceanographic MinosX sound velocimeter. Tides: Tides were corrected during post-processing using two-minute interval averages of the RTK tide data recorded in the "TID" message string of the HYPACK navigation file for each survey line. VDatum transformation grid “MENHMAgome01_8301” was used within the HYPACK software for the kinematic tide correction process during 2013-003-FA to offset water level heights from the WGS84 ellipsoid to MLLW. See the HYPACK navigation files metadata for additional information "2013-003-FA_HYPACK_meta.xml" available from the larger work citation. Remaining artifacts: 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.
  2. How were the data generated, processed, and modified?
    Date: 2013 (process 1 of 7)
    1. Raw to Processed conversion for USGS field activity 2013-003-FA: Each raw SWATHPlus bathymetric sonar file (SXR) was converted to SWATHPlus processed file (SXP) using SEA SWATHPlus Swath Processor (ver. 3.07.17). 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. Several bathymetric filters were applied to remove erroneous soundings and reduce the density of the data. 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 (0-4m), box (3-50m depth, 1.5-75m horizontal), median (window size 5), alongtrack 1 (depth difference of 5-m, window size 5-m, and learn rate of 0.7), alongtrack 2 (depth difference of 1.5-m, window size 1m, and learn rate of 0.9), and mean filters (0.25m). 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
    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 7)
    2. CARIS processing for USGS field activity 2013-003-FA: A new CARIS HIPS project (ver. 8.0) was created for this field activity with projection information set to Universal Transverse Mercator (UTM) Zone 19, WGS84. Each SWATHPlus processed file (sxp) was imported to the new CARIS project using the Import/Conversion Wizard. A 5 meter resolution Bathymetric and Statistical Error (BASE) Surface was created from the files for each Julian day. The BASE surface for each day was reviewed for any inconsistencies or data anomalies. Navigation was reviewed and edited as needed using the navigation editor tool. Beam-to-beam slopes and across track angle filters were applied to the soundings line by line. 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. Preliminary processing was done during the survey and additional processing was done post-survey with CARIS HIPS and SIPS versions 8.0, 8.1 and 9.0. This process step was done between 2013 and 2015.
    Date: 2015 (process 3 of 7)
    3. Prepare and apply RTK Tide data for USGS field activity 2013-003-FA: A tidal correction file was created during post-processing by applying a two-minute moving median filter to the RTK tide data recorded in the "TID" message string of the raw HYPACK navigation files. The TID messages from device 1 (DEV 1; which was the NovAtel DL-V3 GPS receiver) were extracted using a shell script called web_novTid_movmed and a Python script called tid_movmed.py. Only HYPACK extracted tide data were used for this survey. RTK tide corrections were loaded and applied to the soundings line by line in CARIS, resulting in bathymetric values referenced to MLLW. Each line was re-merged and the preliminary BASE surfaces were recomputed to incorporate the new tide information. Additional swath editing was done in CARIS using the swath and area based editors to remove any additional inconsistencies and minimize survey artifacts. This process step was done between 2013 and 2015. Data sources produced in this process:
    • 2013_003MasterTide.tid
    Date: 2016 (process 4 of 7)
    4. Final BASE surface creation and export: Three separate 5-meter BASE surfaces were created for the (1) east-west trending lines south of Martha's Vineyard; (2) the north-south trending lines south of Martha's Vineyard and east of Noman's Land; and (3) the area north of Nantucket utilizing all the quality bathymetric soundings data from the survey. An interpolation algorithm was run on each of these BASE surfaces in CARIS HIPS/SIPS to fill small gaps between lines. The BASE surfaces were then combined in CARIS HIPS using the Tools -> Surfaces -> Combine tool (overlapping areas results in the shoalest depth in the resulting surface). The final surface was then exported from CARIS as 32-bit GeoTIFF and as hillshaded GeoTIFF image. Except for setting the sun angle to 40 degrees above the horizon and the vertical exaggeration to 5x, the default hillshade settings were used to create the hillshaded GeoTIFF image. This process step was done between 2015 and 2016. Data sources produced in this process:
    • Bathymetric images (Gridded bathymetric GeoTIFF image - 2013-003-FA_Bath5m_MLLW.tif and depth-colored bathymetric shaded-relief image - 2013-003-FA_BathHlshd5m.tif)
    Date: 20-Jul-2018 (process 5 of 7)
    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: 18-Nov-2019 (process 6 of 7)
    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 7 of 7)
    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?
  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 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?
    USGS Field Activity 2013-003-FA: Vertical accuracy of the raw data based on system specifications may approximate 1% of water depth, 0.1 to 0.4 meters within the survey area. However, overall vertical accuracies on the order of 50-cm or better are assumed based on the following considerations: The Coda Octopus F185R Attitude and Positioning system, used to correct for vessel roll, pitch, heave, and yaw, has a theoretical vertical accuracy of a few mm. Tidal offsets were corrected to MLLW using Real-Time Kinematic GPS (RTK-GPS) heights in post-processing (see process steps). Corrections were sent via cellular modem and VHF radio to the ship from the base station on land. The primary reference station is located at the USGS Marine Operations Facility (MOF) in Falmouth, MA. USGS field tests (unpublished) using submerged targets suggest that the vertical accuracy of the RTK-GPS tidal correction is less than 30cm. Refraction artifacts were minimized by acquiring a range of sound velocity profiles with an ODIM MVP30 moving vessel profiler (until ~0550UTC on JD 156) and a hand-casted AML Oceanographic MinosX sound velocimeter (for the duration of survey 2013-003-FA). Sound velocity data are entered into the SWATHPlus acquisition software to model the sound velocity structure of the water column. Gridding algorithms and cell sizes for these data could introduce errors as great as 3m along the edges of the data, but gridding-induced errors are likely much smaller (less than 20-cm) for most of the survey area. 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 quality main survey line bathymetric data (generally shore parallel) that were collected within the survey areas south of Martha's Vineyard and north of Nantucket were incorporated in this bathymetric surface. Tielines and transit lines were generally excluded from this bathymetric surface, especially if equal or higher quality main survey line data were available. The tieline and transit line data were used to verify tide corrections during post-processing. Line L1f1 was heavily edited due to navigation errors and issues with staying on the survey line. The line was restarted as L1f2, and much of the end of line L1f1 was discarded in swath editing. 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 bathymetric surface represents interpolated data at 5-meter per pixel 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 reduce speed of sound artifacts (refraction). Soundings from the surveys were processed and edited using Computer Aided Resource Information System (CARIS) Hydrographic Information Processing System (HIPS; vers. 8.0, 8.1 and 9.0). 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
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 bathymetry from south of Martha's Vineyard and north of Nantucket (2013-003-FA_Bathy.zip). The zip file contains a folder with the the 32-bit Floating Point GeoTIFF image (2013-003-FA_Bath5m_MLLW.tif) with a world file (2013-003-FA_Bath5m_MLLW.tfw). A depth-colored hillshade bathymetry image (2013-003-FA_BathHlshd5m.tif) with a world file (2013-003-FA_BathHlshd5m.tfw) and metadata files in three standard formats are also included in the zip file. The pixel values in the depth-colored hillshade bathymetry image DO NOT correspond to depths. 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?
    The ZIP file contains a 32-bit Floating Point GeoTIFF image compressed using the DEFLATE compression format with a world file. To utilize these data an image processing or GIS software package capable of viewing a 32-bit Floating Point GeoTIFF image with DEFLATE compression. Standard image viewing software cannot translate a 32-bit floating point GeoTIFF image. The depth-colored hillshade GeoTIFF image is 32-bit GeoTIFF with LZW compression which can be viewed in any image processing or GIS software package capable of viewing a 32-bit GeoTIFF image with LZW 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)

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