Any spurious data points were removed during processing. No duplicate navigation fixes exist for the 500 shots shapefile. Due to the an acquisition software error where the GPS positions were not being written to the SEGY header, the navigation for lines L1-L16 had to be taken from HYPACK navigation files and inserted into the seismic SEG-Y files during post-processing. For each of these survey lines (L1-L16), the HYPACK navigation logging was stopped prior to stopping the seismic acquisition system and therefore the SEG-Y navigation contains several fewer navigation fixes than shots that were recorded in the seismic SEG-Y files (and consequently the resulting PNG images). The remaining lines (L17 and later) have the navigation properly acquired in the SEG-Y header. L1 was collected in Long Island Sound, outside of the Connecticut River (and outside the study area for this project), while testing and calibrating the swath sonar. It is included in this dataset because it was collected in an area of interest to another USGS research project.
Sections of survey data where navigation was recorded but no seismic data were logged are not included. No seismic data were collected during the patch test for the SWATHPlus system and there was no seismic data collected on the transit line 160. Time gaps occurred during this field activity where no surveying was done due equipment problems (Tuesday 18Sept; JD262). On Friday 21Sept (JD265), the last day of the geophysical surveying, only the SWATHPlus sonar was run, no seismic data were collected. Due to the acquisition software error described above for lines L1-L16, the last several shot locations were not recoverable and therefore this dataset of seismic shot navigation reflects fewer shots for L1-L16 than are shown in the seismic PNG images. The average number of missing shots in these 16 survey lines is 30 shots (min:5; max:100) which, at a survey speed of 5 knots, corresponds to approximately 15 meters (min:2.5m; max:51m). The remaining lines (L17 to the end of the survey) have the navigation properly acquired in the SEG-Y header and therefore the number of shots is properly represented in the corresponding PNG images.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Field activity 2012-024-FA: The EdgeTech 424 subbottom profiling system was towed from a starboard-side davit on the R/V Rafael. The navigation for these data were acquired with an Hemisphere Differential Global Positioning System (DGPS) receiver and an antenna mounted on the aft of the R/V Rafael's cabin just port of the centerline. All DGPS data are referenced to WGS84. The SonarWiz 5 acquisition software (version 5.05.0015) logged the navigation coordinates (in arcseconds) to individual trace headers. Layback of 4 meters was accounted for in the acquisition software. The GPS offset to the sheave was x=2.38m, y=0.62m, z=0 but this offset was not set in the acquisition software for lines l1f1 thru l8f1. Beginning with l8f2 all offsets are accounted for in the acquisition software. See note in completeness report about the missing shots from the end of lines L1-L16 that account for, on average, 15 meters of missing navigation for those survey lines. For the remaining survey lines (and for the properly recorded navigation in lines L1-L16), based on previous similar survey parameters, the resulting positional accuracy of the seismic shotpoints is assumed to be better than 10 m; probably on the order of 3-5 meters.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: Unpublished Material
Title: raw seismic navigation
Type_of_Source_Media: disc
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20120915
Ending_Date: 20120920
Source_Currentness_Reference:
ground condition of survey dates: 20120915-20120920; no sonar data were collected on 20120918; no seismic data were collected on 20120921; see Completeness_Report for more information
Source_Citation_Abbreviation: raw data
Source_Contribution:
Seismic-reflection data acquisition 2012-024-FA: Seismic profile data were collected using an EdgeTech 424 subbottom profiling system (frequency modulation swept frequency 4-24 kHz) which was towed from the starboard side of the R/V Rafael. Chesapeake Technologies' SonarWiz 5 acquisition software (version 5.05.0015) was used to control the EdgeTech 3100 portable topside unit, digitally log trace data in SEG-Y rev. 1 format (IEEE floating point), and record GPS navigation coordinates to the SEG-Y trace headers (in arcseconds of latitude and longitude, multiplied by a scalar of 100). During the survey, data were acquired using a 200 milliseconds (ms) shot rate with a 5 ms transit pulse length, logging 60 ms of data per trace. A swept frequency spectrum of 4-24 kHz was used for the entire survey, selectable via SonarWiz communicating with the EdgeTech 3100 topside controller. DGPS navigation was supplied by a Hemisphere receiver with the antenna mounted on the aft of the R/V Rafael's cabin just port of the centerline. Cable layback is 4 meters, depth below water line 0.5 meters. GPS offset from sheave: x=2.38m, y=0.62m, z=0. These values were entered into SonarWiz starting with line l8f2 (see note in horizontal position accuracy above). Seismic-reflection data were processed using SIOSEIS (2011) and Seismic Unix (Cohen and Stockwell, 2011).
Process_Step:
Process_Description:
SIOSEIS (version 2010.2.25) was used to read SEG-Y files, renumber shots starting from one, 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. This process step and all subsequent process steps were performed by the same person - Seth Ackerman, unless otherwise noted.
Process_Date: 201209
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Seth Ackerman
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: 508-548-8700 x2315
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: sackerman@usgs.gov
Process_Step:
Process_Description:
The script Read424 (using Seismic Unix version 4.2) was used to read 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). Geographic coordinates (WGS84) were converted to UTM zone 18 coordinates (WGS 84) using Proj (version 4.6.0). Header information from each SEG-Y file was saved to CSV text files after an AWK (no version) filter was used to maintain the first and last shots, shots at multiples of 500, and shots with unique navigation coordinates. End shots and shots at multiples of 500 may not have unique navigation coordinates. A 500 shot interval was chosen because it corresponds to the annotation interval provided along the top of the seismic-reflection profile PNG images. In the process of extracting the navigation from the SEG-Y files and saving it to the CSV files, a temporary plot is made to visually check the navigation fixes and identify if there are any issues or extreme outliers.
Process_Date: 201209
Process_Step:
Process_Description:
As noted in the Logical Consistency and Completeness Reports above; there was an acquisition error where no navigation was being written to the SEGY header for survey lines L1-L16 for the EdgeTech 424 system. The navigation for lines L1-L16 were manually processed to create unique and 500-shot point CSV files similar to those that were generated by the Read424 script for the rest of the EdgeTech 424 survey data as described in the previous process step. Data from the Read424 process described above provided the time, shot number and line name for each survey line (L1-L16). Then a series of ad hoc AWK scripts and some manually editing was used to:
1. parse and reformat the DEV 0 (Hemisphere DGPS) POS data messages from the HYPACK navigation files associated with L1-L16
2. join the HYPACK navigation data with the output from the Read424 script for lines L1-L16
3. convert the Easting/Northing coordinates to latitude/longitude (using Proj; version 4.6.0), reformat the data to match the other unique and 500-shot CSV files.
Process_Date: 20120922
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David Foster
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: 508-548-8700 x2271
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: dfoster@usgs.gov
Process_Step:
Process_Description:
A Python script 424intoSQL12024.py, originally written by Wayne Baldwin, is used to import the CSV text files containing navigation information into the SpatialLite (version 4.3.0a) enabled SQLite (version 3.7.9) database. The geographic locations for each shot point were used to create point and line feature geometries in the SQL database. Additional survey information is populated in the SQL database including identifiers for the survey name, vessel, and seismic equipment used.
Process_Date: 20161024
Process_Step:
Process_Description:
An Esri point shapefile for the 500-shotpoint intervals was exported directly from the SQLite database using spatialite_tools (ver. 4.1.1).
spatialite_tool -e -shp 2012-024-FA_SeismicShot500 -d ./2012-024-FA-SQLdb.sqlite -t SeisSht500_pt -g geom_500 -c CP1252 -s 4326 --type POINT
Process_Step:
Process_Description:
CSV files for the unique shot navigation data and the 500 interval shot navigation (including the beginning and end shot) were exported from the SQLite database using Geospatial Data Library (GDAL 2.0.1) ogr2ogr executable with the Spatialite option and an SQL query.
ogr2ogr -f "CSV" 2012-024-FA_424_shotunique.csv 2012-024-FA-SQLdb.sqlite -dsco SPATIALITE=yes -sql "SELECT * FROM SeisUnique_pt"
ogr2ogr -f "CSV" 2012-024-FA_424_shot500.csv 2012-024-FA-SQLdb.sqlite -dsco SPATIALITE=yes -sql "SELECT * FROM SeisSht500_pt"
The file '2012-024-FA_424_shotunique.csv', which is provided in the zip-compressed package of the 500-shot shapefile '2012-024-FA_SeismicShot500.zip', contains the unique navigation. The file '2012-024-FA_424_shot500.csv, in the same zip file, contains the beginning, ending, and 500 shot interval positions.
Process_Step:
Process_Description:
XTools Pro (version 12.0) for ArcGIS desktop was used (Table Operations - Table Restructure) to clean up the attribute headings in the polyline shapefile's attribute table. The ImageName field was updated to reflect the renamed seismic image names with the field activity prepended to the line name. The ImageName fields in both of the CSV files (2012-024-FA_424_shotunique.csv and 2012-024-FA_SeismicShot500) were updated as well.
Process_Date: 201709
Process_Step:
Process_Description:
Added keywords section with USGS persistent identifier as theme keyword.
Process_Date: 20200908
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: VeeAnn A. Cross
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: 508-548-8700 x2251
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: vatnipp@usgs.gov
