Shot point navigation at even 500 shot intervals for EdgeTech SB-512i chirp seismic-reflection data collected in 2015 by the U.S. Geological Survey along the Delmarva Peninsula, MD and VA (Esri point shapefile, GCS WGS 84)

Scripts within SIOSEIS (version 2013.1.1) and Seismic Unix (version 4.2) were used to process SEG-Y data, create navigation files, and plot images. The processing flow and scripts used to produce navigation files including trackline shapefiles and shot points are summarized below and in the following processing steps.
1. SIOSEIS (version 2013.1.1) was used to read SEG-Y files, renumber shots starting from one, extract the envelope-detected trace, and write out new SEG-Y files. The original shot numbers, which were assigned by SonarWiz sequentially over the duration of an acquisition session despite SEG-Y file changes, are preserved in the raw SEG-Y data.
2. The SIOSEIS script Sio_medianstk was used to minimize S-boom cross talk (when multi-channel streamer lines were recorded simultaneously: Julian day 161-168) with a two-trace median stack (trim 50 percent of the values furthest from the median amplitude) and improve water bottom picking. This script was used for all lines even after multi-channel streamer was turned off, due to the improvements made to water bottom picks.
3. The script Read512i_mstk was used to read median filtered stacked and renumbered 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). Header information from each SEG-Y file was saved to text files after an AWK (no version) filter was used to maintain the first and last shots, shots at multiples of 100, 500, and shots with unique navigation coordinates. Geographic coordinates (WGS 84) were converted to UTM zone 18 N coordinates (WGS 84) using Proj (version 4.6.0). End shots and shots at multiples of 100 may not have unique navigation coordinates. Separate text files containing the first and last shots and even 500 shot intervals were also saved. A 500 shot interval was chosen because it corresponds to the annotation interval provided along the top of the seismic-reflection profile images. Read512i_mstk called a Python script 512itoSQL15001.py, written by Wayne Baldwin, which imported the CSV files to the SpatialLite (version 3.0.1) enabled SQLite (version 3.7.9) database. Esri shape polyline and shot point files were exported directly from the SQLite database.

The online links to the data were updated to reflect the new server hosting the data. Additionally, other small edits could be made to the metadata, such as modifying http to https where appropriate. The metadata date (but not the metadata creator) was edited to reflect the date of these changes.

Added keywords section with USGS persistent identifier as theme keyword.