Color Shaded-Relief GeoTIFF Image Showing the 2-m Bathymetry Generated from National Oceanic and Atmospheric Administration (NOAA) Survey H11445 North of Plum Island, New York (H11445_MB2M_UTM.TIF, UTM Zone 18, NAD83)

Bathymetric data were acquired in extended Triton data format (XTF) and recorded digitally through an ISIS data acquisition system. Reson 8101 and 8125 multibeam echosounders hull-mounted on two 29' launches deployed from the NOAA ship Thomas Jefferson were used to acquire the sounding data. All positioning and attitude were determined with Trimble DSM212L DGPS receivers and Applanix POS/MV Model 320 v.4 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 three to four hours of multibeam acquisition. Tidal zone corrections were calculated from data acquired at the New London, Thames River, CT tidal gauge. The vertical resolution of the multibeam data is approximately 0.5% of the water depth. The data were gridded to 2-m resolution and saved as a CARIS HIPS database. Vertical datum is mean lower low water; X and Y units are meters; UTM Zone 18, NAD83.

The fieldsheet from survey H11445 (average depths, not the shoal based fieldsheets) was imported into the Fledermaus v6.7 program DMagic to make an equivalent digital terrain model (DTM) file. The floating point format for each sounding depth point is preserved during data import. Additionally, this fieldsheet was imported into DMagic as "gridded data", therefore re-gridding of data did not occur during the import process and thus preserved the original resolutions of the CARIS fieldsheet: H11445 2 meter cell size.

In DMagic, a shaded relief image was created using the surface shader tool. Parameters: Shade direction at 0 degrees (from the north), elevation 55 degrees, vertical exaggeration 4X.

Using the Fledermaus v6.7 program Imageviewer, the shaded relief image created in the previous step was exported in the TIFF image format with an associated ESRI world file containing georeferencing information. The TIFF image is projected in the UTM coordinate system using zone 18N, and the datum is NAD 83.

Used Photoshop CS2 to change the background of TIFF to white and saved without compression.

Used GeoTifExamine to update georeferencing in the header of the TIFF based on the world file, making the TIFF a GeoTIFF.

Defined projection as UTM 18, NAD 83 using ArcCatalog 9.2 Define Projection Tool, so ArcMap can project the data.

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.). 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.