USGS Home
Contact USGS
Search USGS

Navigation Data and Maps

Two versions of navigation maps are provided in this Data Series. The first set consists of trackline maps, which represent vessel position during the survey, since the navigation data used to create these maps have not been corrected for the offset between the GPS antenna and the towfish (figure 1).  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. For more information about the GIS project, refer to the Software page. The second set of included navigation maps is line navigation maps. With these maps, the GPS offset has been applied, and therefore the maps show the location of the towfish.

Trackline Maps

The trackline maps also contain links to the geospatial profiles.

Full Survey Area Location Map

• 10CCT01 Location Map
• 10CCT02 Location Map
  • Area 1
  • Area 2
  • Area 3
  • Area 4
• 10CCT03 Location Map
  • Area 1
  • Area 2

Line Navigation Maps

The line navigation maps, which have been corrected for the GPS offset mentioned above, 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.

Processed Shotpoint Navigation

In addition to shotpoint navigation files, 1,000-shot-interval files were generated to help correlate shot locations on the map with evenly spaced 1,000-shot index markers along the top of the printable profile images. Both 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 readll_chirp script. Shotpoint coordinates were then projected from latitude and longitude coordinates to 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. 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
10cct01 (20.1MB ASCII text file)
10cct02(129 MB ASCII text file)
10cct03 (38.2 MB ASCII text file)

Processed 1,000-Shot-Interval Location Navigation
s10cct01 (19.7 KB ASCII text file)
s10cct02 (131 KB ASCII text file)
s10cct03 (38.0 MB 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. 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)