Seismic-Reflection Profiles in SEG-Y Format From Western Rhode Island Sound (1980)

Original analog seismic records of cruise NECH80-1 were obtained using a towed EG&G Uniboom system with a half-second fire rate. The signal was amplified and filtered to a 400- to 4000-Hz bandpass. The seismic data have 1- to 2-m resolution. Seismic data were printed on EPC recorders at a quarter-second sweep rate.

Original seismic records were scanned at 300 dpi, 8-bit grayscale on an Ideal Contex Crystal TX 40 scanner using Ideal ScanOS version 2.5.4 software and saved as TIFFs, after being roughly rotated and cropped. Some seismic lines were too long to scan at once and were cut into sections, other lines were collected in sections. These sections are noted in the file names with lower-case letters after the line number. For instance, n80_102Ac.tif signifies the cruise as R/V NEECHO in 1980 (NECH80-1), line 02A, section c, and TIFF format. Capitalized letters are part of the original line number, as recorded in the logbook and on the seismic line.

TIFFs were then opened in Adobe Photoshop CS2 and saved as 200 dpi grayscale TIFFs.

Grayscale TIFFs were further processed in Adobe Photoshop CS2 in order to aid in creating the SEG-Y files. These TIFF images were rotated so they were nearly perfectly horizontal, cropped to start and end shots with known positions, and resampled using bicubic filtering, such that each horizontal pixel of the image corresponds to a trace and each vertical pixel corresponds to a time sample, based on a 0.5 second fire rate and 0.25 sec sweep rate (250 ms) and an assumed 0.08 sample rate. For instance, a 30-minute image is 3600 shots/pixels wide (30*60/0.5) and 3125 pixels high (250 ms/0.08 ms). Seismic-reflection profiles that had noted changes in ship speed or places where recording stopped for belt changes were split into segments, so each file was obtained at roughly the same speed. These segments are labeled with _1, _2, or _3 after the section, thus the file names differ slightly from the line names as used in the logbook. Since TIFF images were clipped in the process of making SEG-Y files, users are encouraged to view the TIFF images available in this report (https://pubs.usgs.gov/of/2009/1002/html/wris_prof.html) in order to see field notes related to data acquisition and weather conditions, which were written directly on the paper records.

Rotated, cropped, and resampled grayscale TIFFs were run through tif2segy, a Unix shell script written by Andrew MacRae (Saint Mary's University, Nova Scotia) and used to convert TIFFs to SEG-Y format. Tif2segy requires two other programs to run successfully: Seismic Unix (http://www.cwp.mines.edu/cwpcodes) and Netpbm tools (http://netpbm.sourceforge.net). Quality control was performed by viewing the SEG-Y files using SeisVU SEG-Y File Viewer (1.0.0.1).

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.). Attempted to modify http to https where appropriate. Fixed the date format in the time period of content. Online link was added to a cross-reference and fixed an online link in another cross-reference. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. 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.

Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.

Additional information regarding file availability through GeoMapApp was added to the metadata. This included an additional distribution link pointing to CMGDS.

Added keywords section with USGS persistent identifier as theme keyword.