Enhanced SIS-1000 sidescan sonar mosaic of a minibasin on the Louisiana upper continental slope - UTM, zone 15, WGS84 (SIS_ENUTM.TIF)

Sidescan sonar data were collected using a Benthos SIS-1000 sidescan sonar system and logged to a Triton/ELICS QMIPS data logging computer.

The digital sidescan data were copied from the logging computer and then processed and mapped to provide proper geographic locations of features identified in the imagery. The first processing step was to edit the navigation to generate the best tow-vehicle navigation possible. A full description of the navigation processing steps is given by Foster and others (2000). The next set of processing steps included subsampling the raw sidescan data using a median filtering routine to suppress speckle noise and reduce file size, merging these image files with the edited navigation and then correcting for slant-range distortion and signal attenuation using XSonar (Danforth and others, 1991). After these steps the data were imported to the WHIPS software (Paskevich, 1992) and high- and low-pass filtering routines were used to reduce the noise associated with dropped sonar lines. Once the processing of individual strips was completed the imagery was mapped to its proper geographic location using techniques summarized by Paskevich (1996). The data were mapped in UTM (zone 15) using the WGS 84 datum at a 2-m pixel size. The navigation processing was done by David Foster, the XSonar processing by William Danforth, and the WHIPS processing and mapping by VeeAnn Cross.

Non-overlapping swaths of sonar imagery were brought into the PCI remote sensing software and combined to create a composite digital mosaic. The techniques used to generate the composite digital sidescan mosaic are summarized by Paskevich (1992). This process step was completed by David Twichell

A linear stretch was applied in PCI to the sidescan image to enhance the image. The data between values of 15 and 80 were spread across the full 8-bit range (0-255). High-backscatter (values near 255) in this image is white and low-backscatter (values near 0) is black. This step was completed by David Twichell.

The enhanced image mosaic was exported from the PCI 'pix' database as a GEOTIFF image with an associated "world" file. The completed mosaic has a 2-m pixel size.

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.). The link to the data in the Distribution_Information section had to be fixed. Attempted to modify http to https where appropriate. The link to the larger work citation had to be fixed. Online links were added to the cross-references. 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.