4 meter composite sidescan sonar mosaic of the New York Bight Apex (APEX_OF.TIF)

The sidescan-sonar data were acquired with a Datasonics SIS 1000 CHIRP sonar system, which operates in a frequency range of 100 - 120 kHz. The sidescan-sonar imagery of the New York Bight region is comprised of data acquired on seven geophysical cruises operated by the USGS during 1995 - 1998. All sidescan-sonar data were logged digitally at a sample rate resulting in a 0.18-m pixel size in the across-track direction and approximately 0.14-m in the along-track direction following the methodology outlined in Danforth and others (1991). A median filtering routine (Malinverno and others, 1990) was applied to the sidescan-sonar data to remove speckle noise, resulting in a 0.73-m pixel size. The data for each survey were further processed and digitally mosaicked using PCI Geomatica Software and procedures described in Danforth and others (1991), Danforth (1997), and Paskevich (1992) resulting in an enhanced, geographically correct, sidescan-sonar mosaic with 4 meters/pixel resolution. The seven individual images were then mosaicked to form one composite sidescan-sonar image for the New York Bight region. The composite mosaic has a resolution of 16 meters/pixel. The composite mosaic was exported as a TIFF image, with an associated ESRI world file.

The sidescan-sonar image was clipped to the extent of the 1995 and 1996 geophysical surveys using the GRIDCLIP script within ArcView 3.2.

The TIFF image (sonar.tif) was compressed using LizardTech, MrSID GeoSpatial Encoder 1.3.1. This software compresses the image at a specified ratio, which is 20:1 by default. An associated sdw file accompanies the .sid file. The .sdw is an ESRI world file for the given .sid image file. In order to view these data within ArcView, the MrSID Image Support extension must be loaded. Once, the extension is loaded, the .sid image file can be loaded into ArcView as an Image.

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.). Reformatted the source contribution information - adding the information that the data are not available online. 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.