U.S. Geological Survey Data Series 620
Trackline maps were created with ESRI ArcGIS 9.3 software, exported to Adobe Illustrator for further editing, and saved in JPEG format. These images can be accessed through the links provided below or from within the cruisenav folder. The navigation data used to create these maps have not been corrected for the offset between the shotpoint and GPS antenna (fig. 1). For more information about the GIS project, refer to the Software page.
The trackline maps contain links to the geospatial profiles, printable profiles, and line navigation maps. The line navigation maps, which have been corrected for the GPS offset, were created with CTI SonarWeb software and are stored in the linenav folder. Refer to the Profiles page for more information about the geospatial and printable profiles.
In addition to shotpoint navigation files, 1,000-shot-interval files were generated to help locate shot locations on the map with features identified on the profiles. Both shotpoint navigation files and 1000-shot-interval location files were extracted from the trace headers of each line using Seismic Unix software via the readll_chirp script. These files were then processed with PROJ.4 software (http://trac.osgeo.org/proj/) to generate UTM coordinates from latitude and longitude coordinates and reformatted for use with ESRI GIS software. The processed navigation data have not been corrected for the offsets between the shotpoint and GPS antenna (fig. 1).
The processed shotpoint navigation and 1,000-shot-interval location files can be accessed through the links provided below or from within the nav folder. Each ASCII text file contains eight fields separated by commas and defined as follows:
Field 1: UTM X (Zone 16)
Field 2: UTM Y (Zone 16)
Field 3: Trackline Number
Field 4: Shotpoint Number
Field 5: Longitude (decimal degrees)
Field 6: Latitude (decimal degrees)
Field 7: Year
Field 8: Day of Year:Hour:Minute:Second (UTC)
Processed Shotpoint Navigation (14.7-MB ASCII text file)
Processed 1,000-Shot-Interval Location Navigation (53.2-KB ASCII text file)
Shotpoint navigation files were extracted from the trace headers of each line using Seismic Unix software. Unprocessed navigation files are stored as ASCII text files in the rawnav folder by trackline number. These navigation data have not been corrected for the offset between the shotpoint and GPS antenna. Each file contains six fields separated by a space and defined as follows:
Field 1: Trackline Number
Field 2: Shotpoint Number
Field 3: Longitude (decimal degrees)
Field 4: Latitude (decimal degrees)
Field 5: Year
Field 6: Day of Year:Hour:Minute:Second (UTC)
NOTE: During data collection of lines 08i71 - 08i79, the navigation system failed; consequently, only one latitude and longitude fix (-88.936298 30.204590, the first shot of 08i71) was recorded. This single navigation fix was subsequently assigned to all the preceding lines in both the raw and processed shotpoint navigation files.