Color Shaded-Relief GeoTIFF Image Showing the 25-m Bathymetry Generated from National Oceanic and Atmospheric Administration (NOAA) Survey H11346 in the vicinity of Edgartown Harbor, MA (H11346_MB25M_GEO.TIF, Geographic, WGS84)

The bathymetry data were acquired in XTF (extended Triton data format) and recorded digitally through an ISIS data acquisition system. Reson 8101 and 8125 multibeam echosounders and Odom vertical-beam echosounders hull-mounted on 29' launches deployed from the NOAA ship Thomas Jefferson were used to acquire the sounding data. All positioning and attitude were determined with TSS POS/MV 320 DGPS-aided inertial navigation systems. The data were processed using CARIS HIPS (Hydrographic Image Processing System) software for quality control, and to incorporate sound velocity and tidal corrections. Sound velocity corrections were derived using frequent SEACAT CTD (conductivity-temperature-depth) profiles. Typically, a CTD cast was conducted every four to six hours of multibeam acquisition. Tidal zone corrections were calculated from data acquired at the Nantucket tidal gauge and a tertiary gauge at Edgartown, MA. The vertical resolution of the multibeam data is approximately 0.5% of the water depth. The data were gridded to 3-m resolution and saved as a CARIS HIPS database. Because the original data are primarily sningle-beam bathymetry, gaps exist between tracklines. Vertical datum is mean lower low water; X and Y units are meters; UTM Zone 19, NAD83.

The CARIS HIPS database was opened in CARIS HIPS/SIPS Caris HIPS/SIPS v6.1 SP2, a 5-m base surface was created in a UTM WGS84 projected CARIS Fieldsheet, and it was exported as ASCII text grid in an XYZ format.

To fill in the gaps of no data and to produce a continuous-coverage dataset, a 25-m grid was created from the 5-m ASCII soundings using Fledermaus v6.7 AvgGrid, and exported as a Fledermaus digital terrain model with a GEO file.

A depth-colored hill-shade file (.shade) was created using Fledermaus v6.7 Data Magician (azimuth 25 degrees, vertical exaggeration 10x, effective sun angle 46 degrees)

Reprojected the .shade file from UTM zone 19 to geographic using Fledermaus ImageViewer v6.7 and then exported the hill-shade file to a TIFF with a world file

Defined projection using ArcCatalog v9.3 and saved projection (.prj) file.

Edits to the metadata were made to fix any errors that MP v 2.9.30 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.). 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.

Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.

Added keywords section with USGS persistent identifier as theme keyword.