Color Shaded-Relief GeoTIFF Image Showing the 2-m Bathymetry Generated from National Oceanic and Atmospheric Administration (NOAA) Survey H11922 in Rhode Island Sound (H11922_2MMB_GEO.TIF, Geographic, WGS84)

Two 8.5-m aluminum Jensen launches and the NOAA Ship Thomas Jefferson were used to acquire the multibeam echosounder (MBES) bathymetric data for survey H11922 during July-August 2008 in Rhode Island Sound west of Gay Head, Massachusetts. The launch MBES data were collected with hull-mounted RESON SeaBat 240-kHz 8101 and 455-kHz 8125 shallow-water systems. These systems measure two-way sound travel time across a 150-degree swath and 120-degree swath, respectively. The SeaBat 8101 has 101 beams at a 1.5-degree beam spacing. The SeaBat 8125 has 240 beams with a cross-track beam width of 0.5 degrees at nadir. The ship's MBES data were collected with a RESON 7125 system which measured two-way sound travel time across a 140-degree swath. Original horizontal resolution of the MBES data was 0.5 m for depths less than 20 m and 2 m for the deeper areas. Vertical resolution of the MBES data is about 0.5% of the water depth. The bathymetric data were acquired in XTF (extended Triton data format) and processed by NOAA using CARIS HIPS (Hydrographic Image Processing System) software for quality control, to incorporate sound velocity and tidal corrections, and to produce the continuous digital terrain model. All positioning and attitude were determined with Trimble DSM212L DGPS receivers and Applanix POS/MV Model 320 v.4 inertial navigation systems; HYPACK MAX was used for acquisition line navigation. Sound velocity corrections were derived using frequent SEACAT CTD (conductivity-temperature-depth) profiles. Typically, a CTD cast was conducted every three to four hours of MBES acquisition. Tidal zone corrections were calculated from data acquired from National Water Level Observation stations at Newport, RI and Menemsha Harbor, MA. Vertical datum is mean lower low water. Individuals interested in detail descriptions of the MBES acquisition and processing should consult the descriptive reports. The data were gridded to 2-m resolution and saved as a CARIS HIPS/SIPS v.6.1 SP2 database in UTM Zone 19, NAD83.

The H11922 CARIS HIPS base surface H11922_Combined_2m_CUBE_Deep_Final (fieldsheet H11922_Combined) was opened in CARIS HIPS/SIPS v7.0 and exported as a UTM Zone 19, NAD83 GeoTIFF image (24-bit, compressed format) using the CARIS HIPS Export Wizard. Sun illumination was from the north at 45 degrees above the horizon. Vertical exaggeration is 5x.

Reprojected the UTM NAD83 GeoTIFF to unprojected geographic, WGS84. Used zeros for the transformation values which is the same as assuming that NAD83 and WGS84 are the same for this area (see reference http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc95-19408.pdf)

Created a world file from the GeoTIFF supplied by NOAA using GeoTIFF Examiner

Edits to the metadata were made to fix any errors that MP v 2.9.32 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). Fixed link to browse graphic. Added depth_encoding method. In the case of the depth resolution, the value of 9999 was entered to indicate that the original metadata did not contain the required information. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent.

Added keywords section with USGS persistent identifier as theme keyword.