OCLOOK(1)

NAME
oclook - provides information from an ocean-tide file

SYNOPSIS
oclook modelfile lat long d | o [polyfile]

oclook modelfile slat nlat wlong elong g [polyfile]

oclook modelfile slat nlat wlong elong r | i | a | p [polyfile]

DESCRIPTION

Oclook is writes to the standard output information about what the ocean-tide value is for a given ocean-tide file, whose name is given on the command line as modelfile. A file which excludes or includes regions through predefined polygons may also be included, as the last argument.

If a single position is given (as north latitude and east longitude), the output may be in one of two forms:

d   In this case the program writes out complete information about the tidal data for this location. The first line of output looks like (for the M2 Schwiderski model, at 33°N, 120°W):

         s are   241   57 (  20761) with fractional locations  -.500  .500

    which gives the cell of the model, indexed both as a matrix (by column and row), and as a 1-d vector. The ``fractional location'' is the coordinates within the cell, relative to the center, with the cell dimensions being 1 by 1. The next lines give the tidal amplitudes in several forms:

              -.3800     .2350
          [     .4468  148.2665 ]
         ne-grid (interpolated) amps (R&I,[amp&ph]) are     -.3973     .2105
          [     .4496  152.0813 ]

    where the first of each pair of lines gives the real and imaginary part, and the second the amplitude (in meters) and Greenwich phase. NOTE that in this, alone amongst these programs, the phase is for a lag, thus corresponding to the phase convention usually used for ocean tides: this is thus, in the usual notation, G. The amplitude is given first for the value in the cell, and secondly for the result of bilinear interpolation to the point given.

o   In this case the program writes out information in the style of a ``load file'' produced by nloadf, but with the only ``load'' being the tidal height in meters; for the example given above this line of output would be

                     .4496 -152.0813

    Note that the phase is now given in the other convention (lags negative), and that this is the interpolated value.

If a range of latitudes and longitudes are given the program lists parameters related to the cells which fall within the specified range. The options are:

g   Write to standard output the coordinates of the corners of the cells (ordered as longitude and latitude), with each set of corner coordinates (five in all) separated by a geographically impossible value. When plotted, these values will thus draw the grid of cells. This output is quite lengthy and should be sent to a file.

r   Write to standard output the coordinates of the centers of the cells, each with the real value of the tide (in meters) for that point.

i   Write to standard output the coordinates of the centers of the cells, each with the imaginary value of the tide for that point (in meters, Greenwich phase, lag positive).

a   Write to standard output the coordinates of the centers of the cells, each with the amplitude of the tide (in meters) for that point.

p   Write to standard output the coordinates of the centers of the cells, each with the phase of the tide for that point (in degrees, Greenwich phase, lag positive).

For example, running the program with option p, and the range being from 32°N to 34°N, -122°E to -120°E, for the Schwiderski M2 model, gives:

      -121.5000   33.5000   165.141
      -121.5000   32.5000   159.497
      -121.5000   31.5000   153.919
      -120.5000   33.5000   159.507
      -120.5000   32.5000   150.027
      -120.5000   31.5000   149.477
      -119.5000   33.5000   151.013
      -119.5000   32.5000   148.267
      -119.5000   31.5000   142.160

The next to last line gives the phase shown for the d option above.

The next two lines show the commands used to generate the model grids shown in Figures 1a and 1b of the supplementary documentation.

oclook m2.csr3tr 20 32 -117 -105 g

oclook m2.cortez 20 32 -117 -105 g

AUTHOR
D. C. Agnew