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Open-File Report 2014–1012

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### Combined Multibeam Bathymetry Data from Rhode Island Sound and Block Island Sound – A Regional Perspective 

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## Methods

| Title PageList of FiguresConversion FactorsAbstractIntroduction**Methods**BathymetryGIS Data CatalogSummaryAcknowledgmentsReferencesContactsIndex | Click on figures for larger images**Figure 2.** Starboard-side view of the National Oceanic and Atmospheric Administration  Ship *Thomas Jefferson* at anchor. **Figure 3.**Launch *3102* being deployed from the National Oceanic and Atmospheric Administration  Ship*Thomas Jefferson*.**Figure 4.**Starboard-side  view of the National Oceanic and Atmospheric Administration launch *3102* at sea.**Figure 5.**The  RESON Seabat 8125 multibeam echosounder  hull-mounted to National Oceanic and Atmospheric Administration launch *3101*.**Figure 6.** The RESON 7125 multibeam echosounder hull-mounted to the National  Oceanographic and Atmospheric Administration Ship *Thomas Jefferson*. **Figure 7.** Brooke Ocean Technology Moving Vessel  Profiler with a Sea-Bird Electronics, Inc. conductivity-temperature-depth profiler used to correct sound velocities for the multibeam data collected  aboard the ship. **Figure 8.** Sea-Bird Electronics, Inc.,  SEACAT conductivity-temperature-depth   profiler. 
The  63-m NOAA Ship *Thomas Jefferson* and  two 8.5-m aluminum Jensen launches (*3101* and *3102*) deployed from the ship  acquired multibeam-echosounder (MBES) data for 14 hydrographic surveys in Rhode  Island and Block Island Sounds over an approximately 1244.5-km² area between  July 2008 and November 2011 (figs. 2, 3, 4). Registry numbers for the completed  surveys include H11922, H11995, H11996, H12009, H12010, H12011, H12015, H12023,  H12033, H12137, H12139, H12296, H12298, and H12299. During 2008, the MBES data were collected with hull-mounted RESON SeaBat  240-kilohertz (kHz) 8101 and 455-kHz 8125 shallow-water systems aboard the  launches and a RESON dual-frequency (200-kHz/400-kHz) 7125 system aboard the  NOAA Ship *Thomas Jefferson*. During 2009 and 2011, the MBES data  were collected with a hull-mounted RESON SeaBat 455-kHz 8125 shallow-water  system aboard launch *3101* (fig. 5) and RESON  single frequency (400-kHz) 7125 systems aboard launch *3102* and the NOAA Ship *Thomas Jefferson* (fig. 6). Original  vertical resolution of the MBES data was 0.5 percent of the water depth. The  bathymetric datasets were acquired and digitally logged with HYPACK and  processed by NOAA using CARIS Hydrographic Image Processing System (HIPS)  software to control quality, incorporate sound velocity and tidal corrections,  and produce the combined bathymetry adjusted for statistical error (BASE)  surfaces.

Horizontal  positioning was by differential global positioning systems (DGPS); HYPACK was  used for acquisition-line navigation. Sound-velocity corrections were derived  with frequent conductivity-temperature-depth profiles. A Brooke Ocean  Technology Moving Vessel Profiler (MVP) with an Applied Microsystems Smart  Sound Velocity and Pressure (SV&P) sensor was used to collect sound-speed  profile data from the ship (fig. 7). Manually  deployed Seabird Electronics SBE-19+ CTD units were used to collect sound speed  profile data from the launches (fig. 8). Tidal-zone  corrections were calculated from data acquired by the National Water Level  Observation Network stations at New London, Conn. (8461490); Newport, R.I.  (8452660);  Menemsha Harbor, Mass.  (8448725); and Montauk, N.Y. (8510560). The vertical datum is mean lower low  water. Detailed descriptions of the MBES acquisition and processing by NOAA can  be found in the Descriptive Reports (National Oceanic and Atmospheric Administration,  2008b, 2008c, 2008d, 2009c, 2009d, 2009e, 2009f, 2009g, 2009h, 2009i, 2009j, 2011b, 2011c, 2011d) and in the Data  Acquisition and Processing Reports (National Oceanic and Atmospheric  Administration, 2008a, 2009b, 2009a, 2011a).

At  the USGS, field sheets from the surveys were read back into the CARIS HIPS software,  combined into a master BASE surface (ricomb) having a 4-m grid resolution, and  exported from CARIS as a Bathymetric Attributed Grid (BAG) file. The BAG  surface was imported as gridded data into Fledermaus to make an equivalent DTM  file, and this file was then directly exported to ArcGIS as a bathymetric  raster file, retaining all of the projection information and grid-cell size.  Vertically exaggerated (5x), hill-shaded (illuminated from 45° north at an  angle of 45° above the horizon) imagery was created by using CARIS HIPS  software; reprojections were performed with ArcGIS data management tools. Metadata  files in the Data Catalog section of  this report contain detailed descriptions of the processing steps used by the  USGS to create the combined datasets. These files can be accessed through the Data Catalog section of this report. The bathymetric grids and imagery released in this report  should not be used for navigation. |
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U.S. Department of the Interior |            U.S. Geological Survey                                                URL: http://pubs.usgs.gov/of/2014/1012/html/methods.html            Page Contact Information: GS Pubs Web Contact                        Page Last Modified: Friday, February 21, 2014, 12:07:19 PM