Multibeam Echosounder, Reson T-20P bathymetry overview (10-m), USGS field activity 2017-003-FA, Mississippi River Delta front offshore of southeastern Louisiana (32-bit GeoTIFF, UTM Zone 16N, NAD 83, NAVD 88 Vertical Datum)

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Frequently anticipated questions:


What does this data set describe?

Title:
Multibeam Echosounder, Reson T-20P bathymetry overview (10-m), USGS field activity 2017-003-FA, Mississippi River Delta front offshore of southeastern Louisiana (32-bit GeoTIFF, UTM Zone 16N, NAD 83, NAVD 88 Vertical Datum)
Abstract:
High resolution bathymetric, sea-floor backscatter, and seismic-reflection data were collected offshore of southeastern Louisiana aboard the research vessel Point Sur on May 19-26, 2017, in an effort to characterize mudflow hazards on the Mississippi River Delta front. As the initial field program of a research cooperative between the U.S. Geological Survey, the Bureau of Ocean Energy Management, and other Federal and academic partners, the primary objective of this cruise was to assess the suitability of sea-floor mapping and shallow subsurface imaging tools in the challenging environmental conditions found across delta fronts (for example, variably distributed water column stratification and widespread biogenic gas in the shallow subsurface). Approximately 675 kilometers (km) of multibeam bathymetry and backscatter data, 420 km of towed chirp data, and 550 km of multichannel seismic data were collected. Varied mudflow (gully, lobe), prodelta morphologies, and structural features were imaged in selected survey areas from Pass a Loutre to Southwest Pass.
Supplemental_Information:
Additional information on the field activity is available from https://cmgds.marine.usgs.gov/fan_info.php?fan=2017-003-FA.
  1. How might this data set be cited?
    U.S. Geological Survey, 2018, Multibeam Echosounder, Reson T-20P bathymetry overview (10-m), USGS field activity 2017-003-FA, Mississippi River Delta front offshore of southeastern Louisiana (32-bit GeoTIFF, UTM Zone 16N, NAD 83, NAVD 88 Vertical Datum): data release DOI:10.5066/F7X929K6, 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.

    Baldwin, Wayne E., Ackerman, Seth D., Worley, Charles R., Danforth, William W., and Chaytor, Jason D., 2018, High-resolution geophysical data collected along the Mississippi River Delta front offshore of southeastern Louisiana, U.S. Geological Survey Field Activity 2017-003-FA: data release DOI:10.5066/F7X929K6, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Baldwin, W.E., Ackerman, S.D., Worley, C.R., Danforth, W.W., and Chaytor, J.D, 2018, High-resolution geophysical data collected along the Mississippi River Delta front offshore of southeastern Louisiana, U.S. Geological Survey Field Activity 2017-003-FA: U.S. Geological Survey data release, https://doi.org/10.5066/F7X929K6.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -89.572538
    East_Bounding_Coordinate: -88.843299
    North_Bounding_Coordinate: 29.384853
    South_Bounding_Coordinate: 28.755905
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5a945c08e4b069906068fab4/?name=2017-003-FA_T20P_Bathy_overview_browse.jpg (JPEG)
    Thumbnail image of 10-m overview multibeam echosounder bathymetry data from the Mississippi River Delta front offshore of southeastern Louisiana.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 21-May-2017
    Ending_Date: 26-May-2017
    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 6843 x 6975 x 1, 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: 16N
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -87
      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 10.0
      Ordinates (y-coordinates) are specified to the nearest 10.0
      Planar coordinates are specified in meters
      The horizontal datum used is D_North_American_1983.
      The ellipsoid used is GRS_1980.
      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: North American Vertical Datum of 1988
      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:
    Elevation values in 32-bit GeoTIFF format. Data values represent depths below the North American Vertical Datum of 1988 (NAVD 88). The "no data" value is set to -32767.
    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?
    U.S. Geological Survey
    Attn: Wayne E. Baldwin
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    US

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

Why was the data set created?

This 10-m per pixel grid provides an overview of processed dual Reson T20P multibeam echosounder bathymetry data along the Mississippi River Delta front offshore of southeastern Louisiana. The grid is intended to provide all of the bathymetry data collected at a broad scale, and be used in conjunction with other geophysical and sample data to investigate sea-floor morphology and geologic framework in the area.

How was the data set created?

  1. From what previous works were the data drawn?
    Reson T20P multibeam echosounder raw bathymetry (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, raw MBES data in HSX format.

    Type_of_Source_Media: disc
    Source_Contribution:
    Multibeam echosounder bathymetry, backscatter, and water column data were collected using dual Reson T20P MBES. The pair of Mills Cross transmit and receive arrays were placed side-by-side within a bracket that oriented them at opposing 30 degree angles (relative to horizontal). The bracket was pole-mounted on the starboard side of the R/V Point Sur so that the sonar arrays were oriented athwart ships (primary and secondary arrays facing outward and down to port and starboard, respectively) and located approximately 3.04 m below the waterline when deployed. Vessel navigation and attitude data were acquired with an Applanix POS MV Wavemaster (model 220, V5) 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 MBES pole approximately amidships on the starboard side of vessel, and the wet pod MRU mounted atop the sonar bracket just aft of the pole. An AML Micro X SV mounted on the sonar bracket monitored sound speed near the sonars during acquisition, and an ODIM MVP30 moving vessel profiler (MVP), mounted on the stern, was used to collect water column sound speed profiles at 1 to 5 hour intervals while underway (See shapefile 2017-003-FA_MVPdata.shp available from the larger work citation). The Reson SeaBat User Interface (version 5.0.0.6) was used to control the sonars, which were operated in intermediate mode at full power (220 db), with frequency modulated pulses between 200 to 300 kHz. The range of the 1024 across track beams formed by the sonars were adjusted manually depending on water depth, and resulted in combined swath widths of 60 to 500 meters or typically 3 to 6 times the water depth. Data were monitored and recorded using the Reson SeaBat User Interface (version 5.0.0.6) and HYPACK/HYSWEEP (version 2017, 17.1.3.0). The SeaBat User Interface logged the navigation, attitude, bathymetry, time-series backscatter, and water column data to s7k format files for each sonar. HYSWEEP logged the navigation, attitude, and bathymetry data for both sonars to a single HSX format file, the time series backscatter data for both sonars to a single 7k format file, and water column data to 7k format files for each sonar. HYPACK HSX data were used to produce the final processed bathymetry grids, and Reson SeaBat User Interface s7k data were used to produce the final processed backscatter mosaics.
  2. How were the data generated, processed, and modified?
    Date: May-2017 (process 1 of 3)
    Shipboard multibeam bathymetry processing within Caris HIPS (version 10.2) consisted of the following flow:
    1) A Caris HIPS project (version 10.2) was created with projection information set to Universal Transverse Mercator (UTM) Zone 16N, WGS 84.
    2) A vessel configuration file was created in Caris for the R/V Point Sur, which included relevant linear and angular installation offsets for each T20P unit as well as vendor specified uncertainty values for each of the survey sensors.
    3) Each HYPACK HSX file was imported to the new Caris project using the Import/Conversion Wizard.
    4) Delayed heave data from raw POS MV files were used to update HIPS survey lines using the import auxiliary data function.
    5) Navigation was reviewed and edited as needed using the Navigation Editor tool.
    6) Sound velocity correction was applied using the Caris algorithm, a master SVP file containing all the sound velocity profiles collected during the cruise and specifying the nearest in distance method, delayed heave source, and use surface sound speed.
    7) Data were merged selecting no tide and the delayed heave source.
    8) 5-m resolution Bathymetry Associated with Statistical Error (BASE) surfaces were created to incorporate files for each Julian day as they were processed, and the BASE surfaces were reviewed for inconsistencies and anomalies.
    9) The swath and subset editors were used to remove spurious points through manual editing and filter application, and 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.
    10) Survey lines adjusted for refraction anomalies were remerged, and the respective BASE surfaces were recomputed to reflect the changes. Shipboard processing was primarily focused on QA/QC during acquisition. Editing processes did require trial and error, and were at times iterative.
    This process step and all subsequent process steps were conducted by the same person - Wayne Baldwin. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Wayne Baldwin
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov
    Date: Nov-2017 (process 2 of 3)
    Post-cruise processing within Caris HIPS (version 10.4) consisted of the following flow:
    1) Post-processed navigation, vessel attitude, and GPS height data from POSPac SBET files, and post-processed rms attitude error data from POSPac smrmsg files were used to update HIPS survey lines using the import auxiliary data function (In some instances, loading of the POSPac SBET data necessitated splitting the HIPS survey lines due to small gaps in the post-processed data; e.g. a and b files for 329_0409, 326_0842, 322_1355, and 322_1935; Additionally, SBET data would not load into data from 5/21/2017 (JD141) between 02:27 and 13:08, and GPS heights were loaded from the raw POS MV files).
    2) Where applicable, lines were updated with Applanix SBET set as the navigation source, and navigation was reviewed and edited as needed using the Navigation Editor tool.
    3) GPS tide was computed using delayed heave data, the vessel water line, and a single datum value of 0 m (referencing the data to the WGS 84 ellipsoid).
    4) Sound velocity correction was reapplied using the Caris algorithm, the master SVP file containing all the sound velocity profiles collected during the cruise and specifying the nearest in distance method, delayed heave source, and use surface sound speed.
    5) Data were remerged selecting the GPS tide and delayed heave sources.
    6) Total Propagated Uncertainty (TPU) was computed specifying POSPac smrmsg and delayed heave values.
    7) A 10-m resolution Combined Uncertainty Bathymetry Estimator (CUBE) surface was created with all files incorporated in the bathymetry overview, using IHO S-44 Order, Special Order specifications, with a Density and Locale Disambiguation method as a CUBE parameter.
    8) Additional editing was conducted using the swath and subset editors to minimize inconsistencies and artifacts, and the CUBE surface was recomputed to reflect the changes.
    Date: Jan-2018 (process 3 of 3)
    Gridded surface export and datum transformation:
    The Caris CUBE surface was exported from HIPS as a 10-m per pixel Esri ASCII raster (UTM Zone 16N, WGS 84), with pixel values (depths) ranging from -34.42 to -306.21 m. The National Oceanic and Atmospheric Administration's Vertical Datum Transformation tool (VDatum version 3.7) was used to transform the Esri ASCII raster WGS 84, UTM 16N, meters to the North American Datum of 1983 (NAD 83), UTM 16N, North American Vertical Datum of 1988 (NAVD 88), meters, using the GEIOD12B geoid model. The resulting Esri ASCII raster was imported into Global Mapper (version 17.1.0) and exported as the 32-bit floating point GeoTIFF image '2017-003-FA_T20P_Bathy_overview.tif', which has pixel values (depths) ranging from -9.75 to -280.86 m.
  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?
    Navigation data were 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 Motion Reference Unit (MRU) 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 MBES pole, approximately amidships on the starboard side of vessel. 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. DGPS positions are horizontally accurate to 0.5 - 2 meters, but accuracy can increase to less than 10 cm after post-processing with Applanix POSPac (version 8.1).
  3. How accurate are the heights or depths?
    Vertical accuracy of the raw data based on system specifications may be approximately 1 percent of water depth (0.1 to 2.8 m within the survey area). The Applanix Wavemaster POS MV Attitude and Positioning system, used to correct for vessel roll, pitch, heave, and yaw, has a theoretical vertical accuracy of a few mm. Post-Processed Kinematic (PPK) GPS height corrections (from Applanix POSPac smoothed best estimate of trajectory (SBET) files) were used to reference soundings to the World Geodetic System 1984 (WGS 84) ellipsoid and remove water depth variations caused by tides. Sound speed profiles (more than 70) acquired with an ODIM MVP30 moving vessel profiler were used during post-processing to minimize acoustic refraction artifacts in the bathymetry data. Changes in ship draft due to water and fuel usage were not considered.
  4. Where are the gaps in the data? What is missing?
    Most of the T20P MBES bathymetry data collected during the cruise are included in this grid. Exceptions are the time periods: 02:27 (UTC) - 03:08 5/21/2017 (JD141), three early patch test lines in which data quality was particularly poor; 12:27 - 12:50 5/23/2017 (JD143), while conducting a POS MV calibration; and 19:19 (UTC) 5/21/17 (JD141) - 02:20 5/22/17 (JD142) and 22:52 5/23/17 (JD143) - 23:03 5/23/17 (JD143), data held from publication at the request of a cooperating agency.
  5. How consistent are the relationships among the observations, including topology?
    This grid represents processed dual Reson T20P multibeam echosounder (MBES) bathymetry data gridded at 10-m resolution. Quality control and data processing were conducted to remove spurious points and reduce sound speed artifacts (refraction) using Computer Aided Resource Information System (Caris) Hydrographic Information Processing System (HIPS; versions 10.2 and 10.4). Despite processing, noticeable vessel motion and refraction artifacts remain in the data, particularly in the area surveyed adjacent to Southwest Pass (see GeoTiff 2017-003-FA_Bathy_swpasssite.tif available from the larger work citation). Several factors contributed to difficulty during acquisition and processing. As the initial deployment of the dual system configuration on a vessel of opportunity, considerable testing and troubleshooting was expected. Environmental conditions were also challenging over the five day cruise, including several periods of inclement weather with high winds and waves and the Mississippi River in flood stage, a combination of factors that certainly contributed to the residual artifacts present in the data. A backscatter mosaic equivalent to this overview bathymetry grid was not published, but backscatter mosaics equivalent to each of three focus bathymetry survey sites during the cruise were published (see GeoTIFFs 2017-003-FA_Backscatter_swpasssite.tif, 2017-003-FA_Bathy_swpasssite.tif, 2017-003-FA_Backscatter_deepsite.tif, 2017-003-FA_Bathy_deepsite.tif, 2017-003-FA_Backscatter_site.tif, and 2017-003-FA_Bathy_site.tif available from the larger work citation). While the navigation and attitude data in the backscatter and bathymetry data are identical, the extents of the processed bathymetry grid and backscatter mosaic differ slightly due to differences in processing of the HYPACK HSX bathymetry and SeaBat User Interface s7k backscatter data.

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)
    U.S. Geological Survey - ScienceBase
    Federal Center
    Denver, CO

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? USGS data release 2017-003-FA multibeam echosounder 10-m bathymetry overview from the Mississippi River Delta front area: includes the GeoTIFF 2017-003-FA_T20P_Bathy_overview.tif, the browse graphic 2017-003-FA_T20P_Bathy_overview_browse.jpg, and the Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (CSDGM) metadata file 2017-003-FA_T20P_Bathy_overview_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?
    To utilize these data, the user must have software capable of viewing GeoTIFF files, or GIS software capable of utilizing web mapping or coverage services.

Who wrote the metadata?

Dates:
Last modified: 06-Mar-2018
Metadata author:
U.S. Geological Survey
Attn: Wayne E. Baldwin
Geologist
384 Woods Hole Rd.
Woods Hole, MA

(508) 548-8700 x2226 (voice)
(508) 457-2310 (FAX)
wbaldwin@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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