Tracklines of chirp seismic-reflection data collected by the U.S. Geological Survey offshore of the Chandeleur Islands, LA, 2006 (seismic_trk_06015.shp, polylines)

A script was run that used SIOSEIS (version 96.4) to strip the single, chirp-processed, envelope trace from the three trace SEG-Y file (real, imaginary, and envelope) recorded by SB-Logger (no version). A new file containing only the envelope trace was saved.

A script was run that used Seismic Unix (version 4.1) to read the SEG-Y files, write a Seismic Unix file, and extract SEG-Y trace header information, which included shot number, longitude, latitude, year, day, and time of day. Geographic coordinates were converted to UTM zone 16 coordinates using PROJ (version 4.6.0). Before saving the header information to a text file, the data were filtered using AWK (no version) to save only unique shot point locations. In addition, a separate text file containing even 500 shot intervals was saved. The 500 shot text file maintains the start and end shots, which may not necessarily by unique fixes. A 500 shot interval was chosen because it corresponds to the annotaion interval provided along the top of the seismic-reflection profile JPEG images, which are included in the "Seisimage" folder of the "GIS_Catalog".

Text files for each seismic line were concatenated into two comma-delimited text files, one containing unique shot point positions ('seismic_shtunique_06015.csv', which is provided in the zip-compressed package of the shapefile 'seismic_sht_06015.shp'), and another containing the 500 shot intervals.

Both concatenated, comma-delimited text files were imported into ArcMap (version 9.2) and saved as points in the ESRI shapefile format.

The point shapefile containing unique shot point positions was used as an input for VACExtras (version 1.97), a VB collection of tools developed by VeeAnn Cross (USGS-WHSC), which converts point data to a new polyline shapefile, based on the order of records contained within one attribute field. The shot number field was used to define the point order. The length of each line segment was calculated and inluded in a new attribute field using Xtools Pro for ArcGIS desktop (version 4.1.0), specifying UTM Zone 16 N - kilometers.

Edits to the metadata were made to fix any errors that MP v 2.9.34 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 source information was incomplete and had to be modified to meet the standard. Formatting of the cross-references was fixed to meet the metadata standard. Minor fixes to the attribute format for some attributes were needed. 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.

Added keywords section with USGS persistent identifier as theme keyword.