SeaMARC 1A sidescan sonar mosaic for the Mississippi Fan

The individual SeaMARC 1A sidescan swaths were transferred from tape to disk. The files were subsequently converted from the QMIPS format to a WHIPS format for processing.

The individual individual swath files were processed using the Woods Hole Image Processing Software (WHIPS). The individual strips were processed to apply geometric (i.e. slant-to-ground range corrections) and radiometric corrections (i.e. beam correction shading).

The SeaMARC 1A files that comprised the eastern half of the survey were transferred to the Woods Hole Field Center's MicroVAX-II computer system. This portion of the survey consisted of mostly straight line segments and were to be digitally mosaicked on this system. (The western portion were done a few months later with developing software). The MicroVAX-II computer system contained the Mini-Image Processing System (MIPS) software that was needed to map and digitally mosaic the data. To begin processing, the WHIPS data files were all converted to MIPS format.

The MIPS data files were spatially mapped using program GEOM. The files were projected and mapped with a Mercator project and a Clarke 1866 spheroid.

As the individual swaths were mapped, they were geo-referenced to the base image, stenciled and mosaiced to the base. (The base was one swath that had been mapped and was selected as the master which everything would be registered with.) Control points were selected interactively to match features on the adjacent lines and a rubber sheeting procedures were applied to the mapped swaths to better align the images. Once registered, a stencil line was interactively drawn around the area of the line to be added. This stencil area was critical as it not only eliminated the unwanted area that was overlapping the adjacent lines but defined the area to be kept. Finally the registered, transformed and stenciled image was added to the base. These steps were repeated for each swath until the eastern mosaic was completed.

The SeaMARC 1A files that comprised the western half of the survey were mapped using the WHIPS software. This area of the survey consisted of several survey line segments. This software could handle curved line segments. The files were projected and mapped with a Mercator project and a Clarke 1866 spheroid to match the eastern portion.

The WHIPS mapped swaths were transferred to the Center's MicroVAX-II computer system for stenciling and mosaicking with the MIPS software. Once transferred to the MicroVAX, the files were converted to the MIPS format for processing.

The converted WHIPS mapped swaths were stenciled and mosaicked with the MIPS software. This procedure is similar to the one outlined for the eastern portion of the survey. Control points were selected interactively to match features on the adjacent lines and a rubber sheeting procedures were applied to the mapped swaths to better align the images. Once registered, a stencil line was interactively drawn around the area of the line to be added. This stencil area was critical as it not only eliminated the unwanted area that was overlapping the adjacent lines but defined the area to be kept. Finally the registered, transformed and stenciled image was added to the base. These steps were repeated for each swath until the western mosaic was completed.

The two completed mosaics, east.pic and west.pic, were combined to create one overall view of the study area.

The MIPS created mosaic, compos.pic, was transferred to a UNIX computer system. The image was imported into a PCI Remote Sensing database file and georeferenced as Mercator.

The mosaic, compos.pix, was reprojected from Mercator to UTM using the PCI Remote Sensing software.

Using the PCI Remote Sensing software, a linear contrast stretch was applied to the SeaMARC 1A sidescan sonar mosaic stored in channel 1. This was done to improve the image's viewing by expanding the data's dynamic range.

The completed, enhanced, 25 m SeaMARC 1A sidescan sonar mosaic was exported from the PCI 'pix' database as a GEOTIFF image with an associated ARC "world" file.

The completed, enhanced, 25 m SeaMARC 1A sidescan sonar mosaic was exported from the PCI 'pix' database as a JPEG image with an associated ARC "world" file.

The completed, unenhanced, 25 m SeaMARC 1A sidescan sonar mosaic was exported from the PCI 'pix' database as a GEOTIFF image with an associated ARC "world" file.

The completed, unehanced, 25 m SeaMARC 1A sidescan sonar mosaic was exported from the PCI 'pix' database as a JPEG image with an associated ARC "world" file.

Edited the metadata to remove errors flagged by MP. Filled out the citation information including adding the edition, suggested citation, adding the DOI link and a link to the data page. Added USGS Thesaurus and ISO 19115 Topic Category theme keywords. Added the link to the browse graphic. Additional small edits to the metadata were made to be consistent with current standards. Updated the distribution liability to an approved FSP disclaimer statement. Updated the distribution format and provided links to the data. The metadata date was updated, but not the metadata contact. The metadata contact email was updated to a valid link with an explanation in the contact instructions (20240717). The metadata available from a harvester may supersede metadata available from the publication. Compare the metadata dates to determine which metadata file is most recent.

Added keywords section with USGS persistent identifier as theme keyword.