Survey lines along which EdgeTech SB-512i chirp seismic-reflection data were collected by the U.S. Geological Survey - Woods Hole Coastal and Marine Science Center offshore of the Gulf Islands, MS, 2010 (ESRI polyline shapefile, 2010-012-FA_SeismicTrackline.shp)

An executable C-shell script called on SIOSEIS (version 10.2.25) to: 1) read the raw SEG-Y data and create shot gathers containing two consecutive traces; 2) create a stacked trace from the two trace gathers while maintaining the navigation coordinates from the header of the first trace in each; and 3) write the stacked traces to new SEG-Y files. This stacking flow ensured that the resulting traces were spaced greater than 0.5 m apart along the trackline, which is a prerequisite for the traces to be loaded into GeoGraphix SeisVision (version R5000) for digital interpretation.

An executable C-shell script called on Seismic Unix (version 4.1) to read the stacked SEG-Y files, write a Seismic Unix file, and extract SEG-Y trace header information, including shot number, longitude, latitude, year, Julian day, and time of day (UTC) to ASCII text files for each survey line. The data were filtered using AWK (no version) to save records for the first and last shots, and shots at unique longitude/latitude positions in between. Geographic coordinates (WGS84) were converted to UTM zone 16 coordinates (WGS84) using Proj (version 4.6.0), and added to the text files in two new columns.

Text files created in the previous step were concatenated into a comma-delimited text file, then imported into ArcMap (version 9.2) using 'Add XY data' and saved as points (Geographic, WGS84) in the ESRI shapefile format.

The shapefile created in the previous step was used as an input for VACExtras (version 1.97), a VB collection of tools developed by VeeAnn Cross (USGS-WHCMSC), which converts point data to a new polyline shapefile ('WHCMSC_SeismicTrackline.shp'), based on record order. The 'FileName' field was used to define which points were used to generate each polyline feature. Using XTools Pro (version 5.2.0) for ArcGIS desktop, the length of each polyline segment was calculated and included in the attribute field 'Length', specifying UTM, Zone 16, WGS84, and kilometers. The "find and replace" option in the ArcMap attribute table viewer was used to modify the 'ImageName' attribute to correctly reflect the relative path of the directory containing the seismic-reflection profile portable network graphic (PNG) images ('GIS_catalog\Seisimage\2010-012-FA\') by replacing the 'l', 'transit', or 'tieline' preceeding each image name with 'pathname' + the preceding characters.

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. Added a landing page link as the first link in the identification section. Updated the link to the field activity. The source information was incomplete and had to be modified to meet the standard. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. Removed an unnecessary Digital_Transfer_Option that contained a bad link. 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.