2-m Bathymetric Grid of National Oceanic and Atmospheric Administration (NOAA) Survey H12012 Offshore in Northeastern Long Island Sound (UTM Zone 18, NAD83, H12012_2M_UTM)

The NOAA Ship Thomas Jefferson was used to acquire the multibeam echosounder (MBES) bathymetric data for survey H12012 during April 2009 offshore in northeastern Long Island Sound. The MBES data were collected aboard the ship 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 1 m for the deeper areas. Vertical resolution of the MBES data is about 0.5% of the water depth. The bathymetric data were acquired and logged with HYPACK Hysweep 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 2009 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 the tide stations at New London and New Haven, Connecticut. Vertical datum is mean lower low water. Individuals interested in detail descriptions of the MBES acquisition and processing should consult the Descriptive and Data Acquisition and Processing reports. The combined data were gridded to 2-m resolution and saved as a CARIS HIPS/SIPS v6.1 SP2 database in UTM Zone 18, NAD83 and as a Fledermaus SD file.

The IVS SD file provided by NOAA NOS (H12012_1_CUBE_NOAA_2m_Final.sd) was opened using IVS DMagic v7.3.1a and the SD surface was exported to an Esri ASCII raster grid (H12012_1_CUBE_NOAA_2m_Final.asc)

The Esri ASCII raster grid file was then imported into ArcMap v9.3.1 and converted to an Esri 32-bit floating point grid using the ASCII to Raster conversion tool (ArcToolbox - Conversion Tools - To Raster - ASCII to Raster).

Defined the projection as UTM Zone 18, NAD83 using ArcCatalog v9.3.1 (ArcToolbox - Data Management Tools - Projections and Transformations - Define Projection).

Edits to the metadata were made to fix any errors that MP v 2.9.36 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.). Attempted to modify http to https where appropriate. Updated the field activity link. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. 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. Adjusted an originator name, 20210923.