Coastal Bathymetry Data Collected in 2016 from the Chandeleur Islands, Louisiana–Interpolated Digital Elevation Model

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Frequently anticipated questions:


What does this data set describe?

Title:
Coastal Bathymetry Data Collected in 2016 from the Chandeleur Islands, Louisiana–Interpolated Digital Elevation Model
Abstract:
The U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (USGS SPCMSC), collected single beam and swath bathymetry data from the northern Chandeleur Islands, Louisiana, in June of 2016. This USGS data release includes the resulting processed elevation point data (xyz) and an interpolated digital elevation model (DEM). This USGS data release provides 437-line kilometers (km) of processed single beam bathymetry (SBB) and interferometric bathymetry (IFB) data collected under Field Activity Number (FAN) 2016-335-FA. This FAN encompasses two subfans each of which represents one survey vessel; the research vessel (RV) Sallenger (subFAN 16BIM01) collected IFB data and the RV Jabba Jaw (subFAN 16BIM02) acquired SB) data. SBB and IFB point data (xyz) are provided in two datums; the International Terrestrial Reference Frame of 2008 (ITRF08) and ellipsoid height and the North American Datum of 1983 (NAD83) in the CORS96 realization for the horizontal and the North American Vertical Datum of 1988 (NAVD88), using the geoid model of 2009 (GEOID09), orthometric height for the vertical. Additional files provided in this data release include: trackline shapefiles, digital and handwritten field logs, and a comprehensive 50-meter (m) DEM. For additional information regarding data collection and processing of the sounding data, please refer to the field logs and formal Federal Geographic Data Committee (FGDC) metadata for the individual IFB and SBB point data (xyz) files and survey trackline shapefiles also included within this publication and available at, https://doi.org/10.5066/P993MBJK.
Supplemental_Information:
Chandeleur_Islands_2016_SBB_and_IFB_ NAD83_NAVD88_GEOID09_50_DEM.tif was derived from the processed swath data are provided as American Standard Code for Information Interchange (ASCII) xyz point data files. These values are not the individual soundings, they are the exported BASE (Bathymetry with Associated Statistical Error) surface at 5-m spatial distances with associated CUBE (Combined Uncertainty and Bathymetry Estimator) sample surface created from the edited soundings dataset using CARIS HIPS and SIPS version 9.1. These are considered interpolated samples in which one value represents all soundings within a five-meter node, weighted by uncertainty and proximity, giving the final value as a data sample within the specific grid cell.
The swath bathymetry data were collected and processed in the World Geodetic System of 1984 (WGS84[1762]) datum, which is equivalent ITRF08. This dataset was transformed from ITRF08 to the NAD83 geodetic datum and NAVD88 orthometric height, using the GEOID09 with the National Oceanic and Atmospheric Administration (NOAA) VDatum version 3.6 transformation software (http://vdatum.noaa.gov/).
The single beam surveys were acquired and processed to a geodetic reference ellipsoid. The single beam data were collected using stand-alone GPS and then post-processed to obtain Differential Global Positioning System (DGPS) navigation. All single beam surveys were collected in WGS84 (G1150), which is equivalent to the International Terrestrial Reference Frame of 2000 (ITRF00). This dataset was transformed from ITRF00 to both ITRF08 and the NAD83 geodetic datum with NAVD88 orthometric height, using the GEOID09 model via NOAA’s VDatum software. The final NAD83/NAVD88 GEOID09 SBB and IFB x,y,z position data from this survey were merged to generate a single point file that was subsequently used to create the interpolated DEM, Chandeleur_Islands_2016_SBB_and_IFB_ NAD83_NAVD88_GEOID09_50_DEM.tif.
  1. How might this data set be cited?
    Farmer, Andrew S., Fredericks, Jake J., Miselis, Jennifer L., Buster, Noreen A., DeWitt, Nancy T., Kelso, Kyle W., Stalk, Chelsea A., and Reynolds, B.J., 20181115, Coastal Bathymetry Data Collected in 2016 from the Chandeleur Islands, Louisiana–Interpolated Digital Elevation Model: U.S. Geological Survey Data Release doi:10.5066/P993MBJK.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.903941
    East_Bounding_Coordinate: -88.832887
    North_Bounding_Coordinate: 30.072349
    South_Bounding_Coordinate: 30.014080
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 10-Jun-2016
    Ending_Date: 19-Jun-2016
    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 127 x 135 x 1, type Grid Cell
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 16
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -87.000000
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 50
      Ordinates (y-coordinates) are specified to the nearest 50
      Planar coordinates are specified in meter
      The horizontal datum used is North American Datum 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: North American Vertical Datum 1988 (GEOID09)
      Depth_Resolution: 0.001
      Depth_Distance_Units: meter
      Depth_Encoding_Method: Implicit coordinate
  7. How does the data set describe geographic features?
    Chandeleur_Islands_2016_SBB_and_IFB_NAD83_NAVD88_GEOID09_50_DEM.tif
    This raster image file (in GeoTIFF format) contains a digital elevation model of processed SBB and IFB xyz data collected in 2016 from the Chandeleur Islands, Louisiana, and provided in the North American Datum 1983 (NAD83) in the CORS96 realization and North American Vertical Datum 1988 (NAVD88), using the geoid model of 2009 (GEOID09). (Source: USGS)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Andrew S. Farmer
    • Jake J. Fredericks
    • Jennifer L. Miselis
    • Noreen A. Buster
    • Nancy T. DeWitt
    • Kyle W. Kelso
    • Chelsea A. Stalk
    • B.J. Reynolds
  2. Who also contributed to the data set?
    U.S. Geological Survey, Coastal and Marine Geology Program, St. Petersburg Coastal and Marine Science Center
  3. To whom should users address questions about the data?
    Andrew S. Farmer
    U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center
    600 4th Street South
    St. Petersburg, FL
    USA

    (727)502-8000 (voice)
    afarmer@usgs.gov

Why was the data set created?

This zip archive contains the 50-m DEM created from the processed IFB and SBB x,y,z data points collected in June 2016 (FAN 2016-335-FA; subFANs 16BIM01 and 16BIM02) around the Chandeleur Islands, Louisiana. The 50-m DEM is provided as a zipped GeoTIFF file with associated metadata. Additional survey and data details are available at https://cmgds.marine.usgs.gov/fan_info.php?fan=2016-335-FA.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 16-Oct-2016 (process 1 of 2)
    Gridding Bathymetric Data: Using Esri ArcGIS 10.3.1, xyz bathymetric point data were used to create a Triangulated Irregular Network (TIN) surface using the 'Create TIN' tool within the 3D Analyst toolbox. The TIN dataset was used to create a gridded raster surface, using the 'TIN to Raster' tool within the 3D Analyst toolbox. The raster was interpolated using the nearest neighbor method with a 50-m cell size.
    Date: 13-Oct-2020 (process 2 of 2)
    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?
    Fredericks, Jake J., Buster, Noreen A., DeWitt, Nancy T., Kelso, Kyle W., and Miselis, Jennifer L., 20161221, Coastal Interferometric Swath Bathymetry Data Collected in 2015 from the Chandeleur Islands, Louisiana: U.S. Geological Survey Data Release doi:10.5066/F7NV9GC8.

    Online Links:


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    The accuracy of the data was determined during data collection. Each dataset used to create the DEM came from singular research vessels during the field activity. Therefore, datasets are internally consistent. Methods were employed to maintain data collection consistency aboard the platforms. During mobilization, each piece of equipment was isolated to obtain internal and external offset measurements with respect to the survey platform. All the critical measurements were recorded manually and digitally entered into their respective programs.
    For the interferometric swath bathymetry, (USGS FAN 2016-335-FA, subFAN 16BIM01), offsets between the sonar head and the DGPS antennas were measured and entered into the Coda Octopus F190R+ internal setup program. The DGPS correction was obtained from the Marinestar High-precision (HP) differential global navigation satellite system, a satellite positioning service, from Fugro, Incorporated (Inc.). This signal was received through the Coda Octopus F190R+ primary GPS antenna. These bathymetric data have not been independently verified for accuracy. The dataset was collected in the native format of WGS84 (G1762), which is equivalent at the centimeter level to the ITRF08.
    For the single-beam survey (USGS FAN 2015-355-FA, subFAN 16BIM02), offsets between the single-beam transducers, the Ashtech antenna reference point (ARP), and the vessel motion units were measured on the roving vessels. All pertinent measurements were accounted for in the DGPS post processing software packages (National Geodetic Survey On-Line Positioning User Service, OPUS, and Waypoint Product Group GrafNav, version 8.6).
    How accurately the DEM represents the data depends on how closely the chosen DEM resolution compares to sounding distribution. For example, there may be hundreds of samples in a 50-m by 50-m cell; however, they are only represented on the surface by a single cell value. Therefore, in cases where terrain slope is high, the gridding formula reduces the actual variability in the sample data.
  2. How accurate are the geographic locations?
    For the IFB: Navigation information was recorded in real-time kinematic mode via the CODA Octopus F190R+ Precision Attitude and Positioning System. Differential GPS correction was obtained through the Marinestar HP broadcast subscription from Fugro, Inc. The manufacturer's stated horizontal accuracy is 10 centimeters (cm) 95% of the time. The trackline position data were recorded using HYPACK version 15.0.1.1 hydrographic acquisition and processing software.
    For the SBB: The USGS-installed benchmark, CTMP, was occupied on the northern Chandeleur Islands for the duration of the field activity, 6/12/16 – 6/16/16. The static GPS base station sessions used On-Line Positioning User Service (OPUS), which is maintained by National Oceanic and Atmospheric Administration (NOAA) and the National Geodetic Survey (NGS). The base location results from OPUS were entered into a spreadsheet to compute one final coordinate and error analysis for that base location. Using the OPUS values for each day, and the total time per GPS session, the average weighted value of occupation time was calculated so the longer occupations hold more value than shorter occupations. The final value for latitude, longitude, and ellipsoid height was the weighted average of each GPS session processed with OPUS. This value was entered into GrafNav version 8.6 as the base station coordinates. The range from the average values was calculated, using outputs from OPUS, for each session as the absolute value of the final value minus the daily value. The maximum horizontal range of the base station coordinates used for post-processing the single-beam bathymetry was 0.00027 decimal seconds latitude and 0.00025 decimal seconds longitude.
  3. How accurate are the heights or depths?
    For the IFB: The manufacturer's stated vertical accuracy of Marinestar GPS subscription is 15 cm, 95% of the time. The Coda Octopus F190R+ inertial measurement unit (IMU), which integrates the Marinestar position with motion, measures vessel velocity (+/- 0.014 meters/second [m/s]), roll and pitch (less than 0.025 degrees), heading (1 m baseline 0.1 degrees), and heave (5 cm/m of depth). The vertical accuracy for the SWATHplus-H system varies with depth and across track range. At 57 m, it is accurate to 10 cm vertically. Maximum vertical transformation error reported by VDatum version 3.6 was 0.076158 m or 7.6158 cm for eastern Louisiana. The sum of the errors (+/- 0.013 m + +/-0.15 m + 0.076158 m) in the vertical direction is equal to +/-0.334 m or +/- 33.4 cm.
    For the SBB: All static base station sessions for CTMP were processed through OPUS. The base location results from OPUS were entered into a spreadsheet to compute a final, time-weighted positional coordinate (latitude, longitude, and ellipsoid height). Base-station position error for each GPS session was calculated as the absolute value of the final position minus the session position value. SPCMSC standards define the maximum acceptable vertical error for any individual base station GPS session as less than or equal to three times the standard deviation of the ellipsoid height; any occupations exceeding this error are removed, and the base station coordinates are then recalculated and considered final. For CTMP base location, the standard deviation of the ellipsoid height was 0.004 m and the maximum difference from the average ellipsoid for any GPS session was 0.013 m.
  4. Where are the gaps in the data? What is missing?
    The data used to create this DEM are complete, post-processed xyz bathymetric data points from acoustic swath and single-beam data collected near the Chandeleur Islands, Louisiana, in June 2016.
  5. How consistent are the relationships among the observations, including topology?
    This file represents the post-processed bathymetric data (xyz) collected during a 2016 bathymetry survey (2016-335-FA). The DEM represents data coverage for the interferometric swath (subFAN 16BIM01) and single-beam bathymetry (subFAN 16BIM02) collected in the nearshore waters surrounding the Chandeleur Islands, Louisiana. Refer to the supplemental information section of the data release for field logs, vessel platform descriptions, and other survey information.

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 should not be used for navigational purposes. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    Andrew S. Farmer
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Physical Scientist/Hydrographic Technician
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    afarmer@usgs.gov
  2. What's the catalog number I need to order this data set? Chandeleur_Islands_2016_SBB_and_IFB_NAD83_NAVD88_GEOID09_50_DEM.tif
  3. What legal disclaimers am I supposed to read?
    This publication was prepared by an agency of the United States Government. Although these data were processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    None

Who wrote the metadata?

Dates:
Last modified: 13-Oct-2020
Metadata author:
Andrew S. Farmer
U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
Physical Scientist/Hydrographic Technician
600 4th Street South
St. Petersburg, FL
USA

(727) 502-8000 (voice)
afarmer@usgs.gov
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/Chandeleur_Islands_2016_SBB_and_IFB_NAD83_NAVD88_GEOID09_50_DEM_metadata.faq.html>
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