Bathymetric Digital Elevation Model (DEM) of the 2016 nearshore coastal bathymetry from West Ship Island to Horn Island, Gulf Islands National Seashore, Mississippi.

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Frequently anticipated questions:


What does this data set describe?

Title:
Bathymetric Digital Elevation Model (DEM) of the 2016 nearshore coastal bathymetry from West Ship Island to Horn Island, Gulf Islands National Seashore, Mississippi.
Abstract:
The United States Geological Survey Saint Petersburg Coastal and Marine Science Center (USGS SPCMSC), in cooperation with the United States Army Corps of Engineers (USACE) conducted bathymetric surveys of the nearshore waters surrounding Ship and Horn Islands, Gulf Islands National Seashore, Mississippi (GUIS). Camille Cut separates Ship Island into East Ship Island and West Ship Island. The objective of this study was to establish base-level elevation conditions around West Ship Island, East Ship Island, Horn Island and their associated active littoral system prior to restoration activities. These activities include the closure of Camille Cut and the placement of sediment in the littoral zone of West Ship Island. This survey will be used to verify sediment migration patterns by monitoring elevation change over time. The dataset produced by this survey will also be compared with historic bathymetric datasets to help further understand island elevation over time. This data release provides 667-line kilometers (km) of processed Single-Beam Bathymetry (SBB) data and 773-line km of processed Interferometric Bathymetry (IFB) collected by the USGS SPCMSC in July 2016 (field activity number [FAN] 2016-347-FA). The IFB data were acquired aboard the Research Vessel (RV) Sallenger (subFAN, 16BIM04), and the SBB data were acquired aboard the RV Jabba Jaw (subFAN, 16BIM05) and the RV Mako (subFAN, 16BIM06). The IFB and SBB point data are provided in three datums: 1) the International Terrestrial Reference Frame of 2000 (ITRF00), ellipsoid height (-49.70 meters [m] to -28.87 m); 2) the North American Datum of 1983 (NAD83) CORS96 realization and the North American Vertical Datum 1988 (NAVD88) with respect to the GEOID12B model (-0.07 m to -20.69 m); and 3) NAD83 (CORS96) and Mean Lower Low Water (MLLW) (-0.04 m to -20.60 m). This metadata record describes the comprehensive, 50-meter (m) Digital Elevation Model (DEM) created from the IFB and SBB point data and provided in NAD83 NAVD88 GEOID12B. For additional information regarding data collection and processing, please refer to the field logs and formal Federal Geographic Data Committee (FGDC) metadata for the individual XYZ point data files and survey trackline shapefiles also included within this data release (https://doi.org/10.5066/F7B8571Q).
Supplemental_Information:
The swath bathymetry data were collected and processed in the World Geodetic System of 1984 (WGS84 [G1762]), which is equivalent at the centimeter level to the International Terrestrial Reference Frame of 2008 (ITRF08). The processed interferometric swath data are provided as a comma delimited, American Standard Code for Information Interchange (ASCII) x,y,z point data file. These values are not the individual soundings but are the exported BASE (Bathymetry with Associated Statistical Error) surface at 5-meter 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. This 5-meter BASE surface was exported as x,y,z point data in comma delimited ASCII format then transformed from ITRF08 to ITRF00 using VDatum version 3.6 for merging with the single-beam dataset. The single-beam surveys were acquired and processed to a geodetic reference ellipsoid. The single-beam data was acquired using stand-alone GPS and then post-processed to obtain Differential Global Positioning System (DGPS) navigation. All single-beam surveys were referenced to World Geodetic System 1984 (WGS84 [G1150]) equivalent to ITRF00. The final x,y,z position data from each survey (IFB and SBB) were transformed separately using VDatum version 3.6 from ITRF00 to NAD83, NAVD88, GEOID12B. The files were then merged to generate a single x,y,z file used to create the DEM. The single-beam surveys were acquired and processed to a geodetic reference ellipsoid. The single-beam data was acquired using stand-alone GPS and then post-processed to obtain Differential Global Positioning System (DGPS) navigation. All single-beam surveys were referenced to WGS84 (G1150) equivalent to ITRF00. The final x,y,z position data from each survey (IFB and SBB) were transformed separately using VDatum version 3.6 from ITRF00 to NAD83, NAVD88, GEOID12B. The files were then merged to generate a single x,y,z file used to create the DEM.
  1. How might this data set be cited?
    DeWitt, Nancy T., Stalk, Chelsea A., Fredericks, Jake J., Flocks, James G., Kelso, Kyle W., Farmer, Andrew S., Tuten, Thomas M., and Buster, Noreen A., 20170930, Bathymetric Digital Elevation Model (DEM) of the 2016 nearshore coastal bathymetry from West Ship Island to Horn Island, Gulf Islands National Seashore, Mississippi.: U.S. Geological Survey Data Release doi:10.5066/F7B8571Q, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -89.003338
    East_Bounding_Coordinate: -88.499847
    North_Bounding_Coordinate: 30.266217
    South_Bounding_Coordinate: 30.187794
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 13-Jul-2016
    Ending_Date: 19-Jul-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 159 x 967 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
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: North American Vertical Datum 1988 (GEOID12B)
      Depth_Resolution: 0.001
      Depth_Distance_Units: meter
      Depth_Encoding_Method: Implicit coordinate
  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)
    • Nancy T. DeWitt
    • Chelsea A. Stalk
    • Jake J. Fredericks
    • James G. Flocks
    • Kyle W. Kelso
    • Andrew S. Farmer
    • Thomas M. Tuten
    • Noreen A. Buster
  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?
    Nancy T. DeWitt
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@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 July 2016 (FAN 2016-347-FA; subFANs 16BIM04, 16BIM05 and 16BIM06) nearshore from West Ship Island to Horn Island, Gulf Islands National Seashore, Mississippi. The 50-m DEM is provided as a zipped GeoTIFF file with associated metadata.

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: 29-Aug-2017 (process 1 of 1)
    Gridding Bathymetric Data: Using Esri ArcGIS 10.4.1, 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 subaerial extent of Ship, Horn, Petit Bois, and Dauphin Island were assigned the regional operational mean high water (MHW) value of 0.23 m (http://pubs.usgs.gov/of/2005/1027/) by soft clipping each TIN to coincident island shoreline shapefiles (1917_shoreline_MSAL.zip and 2007_shoreline_MS.zip available in Buster and Morton, 2011, and the 2015_shoreline_ShipHorn.shp Buster and others, 2017) with elevation values of 0.23 m. TINs were also clipped according to the outer spatial extent of reliable data coverage of each xyz dataset. 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 neighbors method with a 50-m cell size and the processing extent was a common 50-m snap raster used for each of the interpolations to ensure resulting rasters had matching cell center locations allowing for direct comparisons.
  3. What similar or related data should the user be aware of?
    Buster, Noreen A., Brenner, Owen T., and Flocks, James G., 2017, Historical and recent coastal bathymetry data nearshore Ship, Horn, and Petit Bois Islands, Mississippi: U.S. Geological Survey Data Release doi:10.5066/F7B8571Q, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

    This is part of the following larger work.

    Buster, Noreen A., and Morton, Robert A., 20110404, Historical Bathymetry and Bathymetric Change in the Mississippi-Alabama Coastal Region, 1847–2009: U.S. Geological Survey Scientific Investigations Map 3154, U.S. Geological Survey, Coastal and Marine Geology Program, Reston, VA.

    Online Links:

    Weber, Kathryn M., List, Jeffrey H., and Morgan, Karen L.M., 20050101, An Operational Mean High Water Datum for Determination of Shoreline Position from Topographic Lidar Data: U.S. Geological Survey Open-File Report 2005-1027, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal & Marine Science Center, Woods Hole, MA.

    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. These datasets are from individual research cruises and are therefore internally consistent. Methods were employed to maintain data collection consistency aboard the platform. 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 2015-347-FA, subFAN 16BIM04), 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 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 2015-347-FA, subFANs 16BIM05 and 16BIM06), 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 well the DEM represents the data depends on how well 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: The navigation 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 16.1.1.0 hydrographic acquisition and processing software.
    For the SBB: Three benchmark locations were occupied, two on Horn Island and one on Ship Island. On Horn Island, the first benchmark, 202Q 1998 (USACE) was located at the ranger station's trail head south of the pier. The second benchmark WHRN (USGS SPCMSC) was located on the western end of Horn Island atop short sand ridge, on the sound side of the island. The Ship Island benchmark PID BBCL83, stamping 4756 F 2011 (John Oswald and Associates, LLC) was located on the north side of the intersection where the main boardwalk meets the generator shed boardwalk. All the static GPS base station sessions were using the On-Line Positioning User Service (OPUS) maintained by the 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. That is such that longer occupations hold more value than shorter occupations. The final value for latitude, longitude, and ellipsoid was the weighted average of each GPS session processed with OPUS. This value was entered in GrafNav version 8.6 as the base station coordinates. The range from the average value was calculated, using output 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 0.00026 decimal seconds latitude and 0.00049 decimal seconds longitude for 202Q, 0.00038 decimal seconds latitude and 0.00033 decimal seconds longitude for WHRN. The reported error for 4756 F 2011 is 0.013 meters latitude and 0.012 meters 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 per meter (m) of depth). The vertical accuracy for the SWATHplus-H system varies with depth and across track range.
    The IFB data was transformed three times using VDatum version 3.6. The vertical transformation error reported by VDatum is the following: 1) Transformation from ITRF08 to ITRF00 (equivalent to at the centimeter level WGS84 (G1150) is 0.000 m or 0.000 cm for the vertical area named conus (Continental U.S.). Additional non-VDatum reference located at the following link lists transformation from ITRF08 to ITRF00 as -0.01050 m or -1.050 cm(https://confluence.qps.nl/download/attachments/29856813/ITRF_Transformation_Parameters.xlsx); 2)Transformation from ITRF00 to NAD83, NAVD88 with respect to GEOID12B is 0.0762 m or 7.62cm for the vertical area named GEOID12B, and 3) Transformation from NAD83, NAVD88 with respect to GEOID12B to NAD83, MLLW is 0.163 m or 16.30 cm for the vertical area named LAmobile02-8301.
    For the SBB: All static base station sessions for 202Q and WHRN were processed through On-Line Positioning User Service (OPUS) maintained by the 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 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 202Q base location, the standard deviation of the ellipsoid height was 0.010 m and the maximum difference from the average ellipsoid for any GPS session was +/- 0.023 m. For WHRN base location, the standard deviation of the ellipsoid height was 0.002 m and the maximum difference from the average ellipsoid for any GPS session was +/- 0.022 m. For 4756 F 2011 base location only one OPUS session was run so the published coordinates were used. The survey datasheet reports the vertical error of the ellipsoid height as +/- 0.017 m.
    The SBB data were transformed two times using VDatum version 3.6. The vertical transformation error reported by VDatum are the following: 1)Transformation from ITRF00 to NAD83, NAVD88 with respect to GEOID12B is 0.0762 m or 7.62cm for the vertical area named GEOID12B; and 2)Transformation from NAD83, NAVD88 with respect to GEOID12B to NAD83, MLLW is 0.163 m or 16.30 cm for the vertical area named LAmobile02-8301.
  4. Where are the gaps in the data? What is missing?
    The data used to create the DEM are complete, post-processed x,y,z bathymetric data points from acoustic interferometric swath and single-beam data collected in July 2016 from the nearshore waters surrounding Ship and Horn Islands, GUIS, Mississippi.
  5. How consistent are the relationships among the observations, including topology?
    This file represents the post-processed bathymetric data collected during USGS FAN 2015-347-FA. The DEM represents data coverage for the interferometric swath bathymetry (subFAN 16BIM04) and the single-beam bathymetry (subFANs 16BIM05, 16BIM06) collected in the nearshore waters surrounding Ship and Horn Islands, GUIS, Mississippi. 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:
The U.S. Geological Survey requests that it be referenced as the originator of this dataset in any future products or research derived from these data.
Use_Constraints: These data should not be used for navigational purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    Noreen A. Buster
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    nbuster@usgs.gov
  2. What's the catalog number I need to order this data set? Ship_Horn_Island_2016_IFB_SBB_NAD83_NAVD88_GEOID12B_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: 21-Sep-2017
Metadata author:
Nancy T. DeWitt
U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
Geologist
600 4th Street South
St. Petersburg, FL
USA

(727) 502-8000 (voice)
ndewitt@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/Ship_Horn_Island_2016_IFB_SBB_DEM_metadata.faq.html>
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