Knudsen 3202 seismic-reflection data trackline navigation collected by the USGS within Red Brook Harbor, MA, 2009 (RB_SeismicTrackline)

An executable C-shell script called on Seismic Unix (version 4.1) to read the 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. Files for data collected during Julian days 271-282, 288, and 294 were filtered using AWK (no version) to save records for the first and last shots, and shots at unique longitude/latitude positions in between. No navigation was recorded to the SEG-Y trace headers of all lines collected during Julian days 287 and 295, and portions of days 272 (l18f1_001) and 296 (l183f1_001 - l190f1_010), so separately logged 1 Hz DGPS ASCII navigation needed to be merged with the remaining information extracted from the trace headers. This was accomplished using an alternate AWK filter to save shot records for the first and last shots, the first shot recorded at each second, and shots numbers evenly divisible by 500. The VIM (version 7.2.108) text editor was then used to create a new field in each navigation and trace header text file that combined Julian day and UTC time. Finally, using the newly created field as the 'join' field, the Unix JOIN (no version) command was used to merge coordinates from the navigation text file with corresponding shot records in each trace header file based on this Julian day and time field. Geographic coordinates (WGS84) were converted to UTM zone 19 coordinates (WGS84) using Proj (version 4.6.0), and added to the text files in two new columns. VIM was used to add three additional columns to the text files containing the Woods Hole Coastal and Marine Science Center field activity number (SURVEYID), the device used to record the data (DEVICEID), and the vessel used for the survey (VEHICLEID).

Text files containing trace header records for the first and last shots, and shots with unique longitude/latitude positions for each seismic line were concatenated into a comma-delimited text file ('RB_SeismicShot_Unique.csv', which is provided in the zip-compressed package of the shapefile 'RB_SeismicTrackline.shp'), then imported into ArcMap (version 9.2) using 'Add XY data' and saved as points (Geographic, WGS84) in the ESRI shapefile format.

The shapefile containing unique shot point positions, 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 ('RBH_SeismicTrackline.shp'), based on record order. The 'FILENAME' field was used to define which points were used to generate each polyline feature. Also populated during VACExtras polyline creation were fields 'SHOT', 'YEAR', 'JULDAY', and 'SHOT_end'. 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 19 N, 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 JPEG images ('GIS\hyperlink_images\seisimage') by replacing the 'l' preceding each image name with 'pathname' + 'l'. Fields 'SURVID', 'DEVICEID', and 'VEHICLEID' were populated with Field Editor in the attribute table.

Edits to the metadata were made to fix any errors that MP v 2.9.32 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.). Fixed URL in abstract. The source information was incomplete and had to be modified to meet the standard. 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.