Title:
Ship_Horn_Island_2016_IFB_SBB_DEM_metadata: 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).
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.
