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Data Series 924


Navigation Data and Maps


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The trackline map shown below represents the vessel position during the survey; the navigation data used to create this map were not corrected for the offset between the Global Positioning System (GPS) antenna and the chirp's towfish (fig. 2).  The trackline map was created with Environmental Systems Research Institute (ESRI) ArcGIS 10.1 software, exported to Adobe Illustrator for further editing, and saved in Joint Photographic Experts Group (JPEG) format. This image can be accessed through the links provided below or from within the maps folder. For more information about the GIS project, refer to the Software page.

Trackline Maps

13CCT04 Location Map (fig. 3)

Processed Shotpoint Navigation

In addition to shotpoint navigation files, 1,000-shot-interval location files were generated to correlate shot locations on the map with evenly spaced 1,000-shot index markers along the top of the printable profile images. The shotpoint navigation files and 1,000-shot-interval location files were extracted from the trace headers of each line using Seismic Unix software via the readlljsfnew script (located in chirp.tar (52-KB PDF), which can be found in the su folder). Shotpoint coordinates were projected from latitude and longitude coordinates to Universal Transverse Mercator (UTM) northings and eastings (WGS84, Zone 16, meters) using PROJ.4 software (http://trac.osgeo.org/proj/) and reformatted for use with ESRI GIS software. A file containing the location of the start of each line was created for use on the trackline maps. The processed navigation data were not corrected for offsets between the shotpoint and the GPS antenna (fig. 2).

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 (Coordinated Universal Time (UTC))

13cct04.txt - Processed Shotpoint Navigation (87-Megabyte (MB) ASCII text file)

s13cct04.txt - Processed 1,000-Shot-Interval Location Navigation (86-KB ASCII text file)


Raw Shotpoint Navigation

Shotpoint navigation files, consisting of unique navigation fixes, 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 were not corrected for offsets between the shotpoint and the 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)


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