2-m Bathymetric Grid of National Oceanic and Atmospheric Administration (NOAA) Survey H11997 Offshore in Eastern Long Island Sound (H11997_2M_UTM, UTM Zone 18, NAD83)

The NOAA Ship Thomas Jefferson was used to acquire the multibeam echosounder (MBES) bathymetric data for survey H11997 during September 15 - October 29, 2008 offshore in eastern Long Island Sound. 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 a Trimble DSM212L DGPS receiver and an Applanix POS/MV Model 320 v.4 inertial navigation system; HYPACK MAX was used for acquisition line navigation. Sound velocity corrections were derived using frequent SeaCat SBE19 DeepCat CTD (conductivity-temperature-depth) profiles. Casts were made with a Brooke Ocean Technology Moving Vessel Profiler 100 (MVP). Typically, a CTD cast was conducted every three to four hours of MBES acquisition. Sound velocity and pressure in water were measured using a SV&P Smart Sensor housed on the MVP free fall fish. Tidal zone corrections were calculated from data acquired from National Water Level Observation 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 report. The data were gridded to 2-m resolution and saved as a CARIS HIPS database in UTM Zone 18, NAD83.

The gridded Base surface H11997_Combined_2m_CUBE_Deep_Final (fieldsheet H11997_Combined) was imported from the H11997 CARIS HIPS database using Fledermaus v7.1.0beta. Defined input coordinate system as FP_NAD83_UTM_zone_18N, the output coordinate system as FP_NAD83_UTM_zone_18N, and the output SD type as SonarDTM. Created the SD file: H11997_Combined_2m_CUBE_Deep_Final.sd

Exported the SD file to an ArcView grid (ESRI ASCII raster file) using DMagic v7.1.0beta.

The ESRI ASCII raster file was then imported into ArcCatalog v9.3 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 (ArcToolbox - Data Management Tools - Projections and Transformations - Define Projection).

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.). 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.