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Seismic Profiles

Much of the geophysical data collected by the USGS prior to the late 1990s was recorded in analog format and stored as paper copies. Scientists onboard made hand-written annotations onto these records to note latitude and longitude, time, line number, course heading, and geographic points of reference. Each paper roll typically contained numerous survey lines and could reach more than 90 ft in length. All rolls are stored at the USGS FISC-Coastal and Watershed Studies Team (CWST) in St. Petersburg, FL. To preserve the integrity of these records and improve accessibility, analog holdings were converted to digital files. The related GIS information and associated metadata (both formal and informal) were imported into an ESRI ArcSDE geodatabase.

Paper records were scanned at 200 dots per inch (dpi) using an IDEAL/Contex Crystal TX 40-inch (1394) large-format scanner and converted to TIFF format using WIDEimage software (version 2.8.1) in the black and white adaptive mode. Whole roll TIFF images of multiple lines were manually cropped into individual survey lines using WIDEimage. Line images longer than 30,000 pixels were separated into smaller segments for editing with Adobe Photoshop Creative Suite 2 (CS2), where a metadata header file was appended to each survey line or line segment. Images of individual survey lines were named by combining the MASH cruise ID with the survey line (or trackline) number using an underscore, for example, 81CA1_2. If survey lines were longer than 30,000 pixels, the split segments were identified by appending a letter in alphabetical order to the line name, for example, 81CA1_5(a). The metadata header file appended to each line or line segment was created in Adobe Illustrator CS2. These header-merged images were then converted to grayscale, flattened, and saved as TIFFs with lossless (LZW) image compression. To facilitate easy viewing or printing of the scanned profiles on any computing platform using Web browser software, TIFF images were scaled to 25% (with constrained proportions and bicubic resampling) in Photoshop and saved as GIF images.

Survey line TIFF images can be found in the ORIGINALS folder. Metadata header files are located in the HEADERS folder. Printable GIF and TIFF images are stored in the PRINTABLE folder.