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U.S. Geological Survey Data Series 346

Navigation Data and Maps


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Trackline Maps

Trackline maps were created with ESRI ArcGIS 9.2 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 (see fig. 1). For more information about the GIS project, refer to the Software page.

The trackline maps contain links to interactive 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 interactive and printable profiles.

The navigation data written to the "Source coordinates" trace headers (bytes 73 - 80) were used to create the trackline maps; however, these data are only accurate within 1 s of arc, or 32 m. Additional navigation data were recorded more accurately to the "Unassigned" trace headers (bytes 181 - 240) by the acquisition software (Delph Seismic); these data are provided below under the Raw Shotpoint Navigation section. Please see the SEG-Y Format page for a detailed description of the SEG-Y data format including byte number assignments and header value descriptions.

NOTE: No navigation data were written to the SEG-Y headers for shots 1 - 157 of line WR896_1; therefore, the line navigation map and interactive profile for this line were not created, and only a link to the printable profile is provided on the Lake Mabel map.

Location Map


Processed Shotpoint Navigation

Shotpoint navigation files and 500-shot-interval location files were extracted from the trace headers of each line using Seismic Unix software. These files were then processed with PROJ.4 software (http://www.remotesensing.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 offset between the shotpoint and GPS antenna (see fig. 1).

The processed shotpoint navigation and 500-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 17)
Field 2: UTM Y (Zone 17)
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 (21-KB ASCII text file)

Processed 500-Shot-Interval Location Navigation (5-KB ASCII text file)


Raw Shotpoint Navigation

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 (see fig. 1). 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)

The navigation data extracted from the "unassigned" trace headers by Delph Seismic can be found in the DELPHNAV folder.


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