1.  NAME

  btnav2 - Comparison of NAV and BT velocities

  2.  SYNOPSIS

  databtnav2(year_base, data_file, ps_file, plot_title, note )

  3.  DESCRIPTION

  This Matlab function makes a plot of NAV anf BT velocities for
  comparions.  The input ASCII file can be generated with the xtract(1)
  utility and must have the following columns:

  1. Time in decimal days

  2. Longitude in degrees

  3. Latitude in degrees

  4. U ship from ACCESS_VARIABLES

  5. V ship from ACCESS_VARIABLES

  6. Longitude from NAVIGATION

  7. Latitude from NAVIGATION

  8. Speed (in m/s) from NAVIGATION

  9. Direction from NAVIGATION

  10.
     U from BOTTOM_TRACK

  11.
     V from BOTTOM_TRACK

  12.
     Depth from BOTTOM_TRACK

  The return value data is an array with the data from the input file,
  with the additionnal columns:

  1. Ship speed

  2. Ship direction

  3. NAV eastward velocity

  4. NAV northward velocity

  5. BT speed

  6. BT direction

  4.  PARAMETERS

     year_base
        Base year corresponding to the times in the input file.

     data_file
        Name of input data file.

     ps_file
        Name for output postscript file.

     plot_title
        Title for plot.

     note
        Additionnal string to be printed on the plot.

  5.  RETURNS

  This function returns an array with the data from the input data file
  an the addiionnal columns described above.

  6.  AUTHORS

  Pierre Jaccard, Geophysical Institute, University of Bergen, 1999