Single-Beam Bathymetry Data Collected in 2015 nearshore Dauphin Island, Alabama, U.S. Geological Survey (USGS). These data are in the North American Datum 1983 (NAD83) for horizontal component, and the North American Vertical Datum 1988 (NAVD88) with respect to GEOID12A, and Mean Low or Lower Water (MLLW) for the vertical components.
Dauphin Island, Alabama is a barrier island located in the Gulf of Mexico that supports local residence, tourism, commercial infrastructure, and the historical Fort Gaines. During the past decade the island has been impacted by several major hurricanes (Ivan, 2004; Katrina, 2005; Isaac 2012). Storms along with sea level rise, presents a continued threat to island stability. State and federal managers are taking a scientific investigative approach to identify the best options available to formulate and implement a long-term plan to properly restore Dauphin Island and provide resilience against future storms and sea-level rise. Island morphology, including current bathymetry data, is one of several aspects being investigated and funded through a grant from National Fish and Wildlife Foundation Gulf Environmental Benefit Fund. In August 2015, 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) and the state of Alabama conducted bathymetric surveys of the nearshore waters surrounding Dauphin Island. This data release provides 1,165-line kilometers (km) of processed single-beam bathymetry (SBB) data collected by the USGS SPCMSC in August 2015 (Field Activity Number [FAN] 2015-326-FA). Data were acquired aboard 4 separate survey vessels; the RV Sallenger (subFAN, 15BIM10), the RV Jabba Jaw (subFAN, 15BIM11), the RV Shark (subFAN, 15BIM12), and the RV Chum (subFAN, 15BIM13). The data are provided in three datums: 1) the International Terrestrial Reference Frame of 2000 (ITRF00), ellipsoid height (-47.04 meters [m] to -29.36 m); 2) the North American Datum of 1983, realization of CORS96 (NAD83 (CORS96)) horizontal, and the North American Vertical Datum 1988 (NAVD88) vertical (-0.24 m to -17.33 m); and 3) the NAD83 (CORS96) horizontal, and Mean Lower Low Water (MLLW) vertical (-0.12 m to -17.93 m). Additional files include trackline shapefiles, digital and handwritten Field Activity Collection Systems (FACS) logs, a comprehensive 50-meter Digital Elevation Model (DEM), and formal Federal Geographic Data Committee (FGDC) metadata.
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)/ITRF00. The final x,y,z position data from each survey were merged to generate a digital elevation model (DEM) with a cell-size resolution of 50 meters.