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                           NAVIGATION FIELD DATA

                                Description

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The directory rawnav located in directory nav contains the raw navigation
that was collected during the sidescan component of the field program using
a USGS differential GPS system (Ashtech). These files represent the data
that was originally recorded on floppy disk aboard ship. The data are in
NEMA format. WARNING: These data have not been checked for errors. Use with
caution.

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To aid viewing of the original raw navigation data, each data entry was
reformatted (removing the NEMA codes) by filtering the raw data files
through a UNIX awk script. (see README). Every navigation fix from the
original data has been preserved, however.

The navigation is stored in ASCII files using six fields separated by tabs,
with each file representing a separate julian day (i.e. jd179_web.txt).
Navigation fixes are at 10 second intervals. The start and end of each line
is marked within each reformatted navigation file. These files are located
in the NAV sub-directory.

   * Field 1: date and time (julian day:hour (GMT):minute:second)
   * Field 2: Latitude (ie. 32d59.375 = 32 Degrees 59.375' North)
   * Field 3: Longitude (ie. -79d96.875 = 79 Degrees 96.875' West)
   * Field 4: Speed (in knots, computed from the navigation)
   * Field 5: Heading (in degrees, computed from the navigation, i.e.
     course made good)
   * Field 6: Water Depth (derived from an Odem digital echo sounder).
     Depths are in meters, but have not been corrected for the depth of the
     transducer, which was about 2 m below the sea surface, nor for the
     tide (for tidal information and 6 minute tidal data, see NOAA's tide
     server).

[Image] Logbook Summary

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[Image] To Navigation Field data

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