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mgd77track - Plot track-line map of MGD77 cruises


mgd77track NGDC-ids region parameters [ [c][size][,spacing] ] [ [p|s]parameters ] [ f|g|e
] [ -Dastartdate ] [ bstopdate ] [ ] [ d|t|ngap ] [ ignore ] [ ] [ trackticks ] [
-o<flags> ] [ -p<flags> ] [ astartdist[u] ] [ bstopdist[u] ] [ T|t|dms,mc,mfs,mf,mfc ] [
[just/dx/dy/][c|label] ] [ [level] ] [ [-|+][pen] ] [ x_offset ] [ y_offset ] [ -ccopies ]
[ -p<flags> ] [ -t<transp> ]

Note: No space is allowed between the option flag and the associated arguments.


mgd77track reads NGDC MGD77 cruises and creates PostScript code that will plot one or more
ship tracks on a map using the specified projection. The PostScript code is written to
standard output.


Can be one or more of five kinds of specifiers:

1. 8-character NGDC IDs, e.g., 01010083, JA010010etc., etc.

2. 2-character <agency> codes which will return all cruises from each agency.

3. 4-character <agency><vessel> codes, which will return all cruises from those

4. =<list>, where <list> is a table with NGDC IDs, one per line.

5. If nothing is specified we return all cruises in the data base.

(See mgd77info -L for agency and vessel codes). The ".mgd77" or ".nc" extensions
will automatically be appended, if needed (use -I to ignore certain file types).
Cruise files will be looked for first in the current directory and second in all
directories listed in $MGD77_HOME/mgd77_paths.txt [If $MGD77_HOME is not set it
will default to $GMT_SHAREDIR/mgd77].

-Jparameters (more ...)
Select map projection.

west, east, south, and north specify the region of interest, and you may specify
them in decimal degrees or in [+-]dd:mm[:ss.xxx][W|E|S|N] format. Append r if lower
left and upper right map coordinates are given instead of w/e/s/n. The two
shorthands -Rg and -Rd stand for global domain (0/360 and -180/+180 in longitude
respectively, with -90/+90 in latitude). Alternatively for grid creation, give
Rcodelon/lat/nx/ny, where code is a 2-character combination of L, C, R (for left,
center, or right) and T, M, B for top, middle, or bottom. e.g., BL for lower left.
This indicates which point on a rectangular region the lon/lat coordinate refers
to, and the grid dimensions nx and ny with grid spacings via -I is used to create
the corresponding region. Alternatively, specify the name of an existing grid file
and the -R settings (and grid spacing, if applicable) are copied from the grid.
Using -Runit expects projected (Cartesian) coordinates compatible with chosen -J
and we inversely project to determine actual rectangular geographic region. For
perspective view (-p), optionally append /zmin/zmax. In case of perspective view
(-p), a z-range (zmin, zmax) can be appended to indicate the third dimension. This
needs to be done only when using the -Jz option, not when using only the -p option.
In the latter case a perspective view of the plane is plotted, with no third


Append c to annotate using the MGD77 cruise ID [Default uses the filename prefix].
Optional size is the font size in points. The leg annotation font is controlled by
FONT_LABEL. By default, each leg is annotated every time it enters the map region.
Alternatively, append ,spacing to place this label every spacing units apart along
the track. Append one of the units k (km), n (nautical mile), d (day), or h (hour).

-B[p|s]parameters (more ...)
Set map boundary intervals.


Select procedure for along-track distance calculation:
f Flat Earth distances. g Great circle distances [Default]. e Geodesic
distances on current GMT ellipsoid.

Do not plot data collected before startdate (yyyy-mm-ddT[hh:mm:ss]) [Default is
first day].

Do not plot data collected after stopdate (yyyy-mm-ddT[hh:mm:ss]). [Default is last

-F Do not apply the error bit flags if present in a MGD77+ file [Default will apply
these flags upon reading the data].

Let successive point separations exceeding dgap (km) or tgap (minutes) indicate a
break in the track where we should not draw a line [no gaps recognized]. Repeat to
use both types of gap checking. The nN form is used to plot only one every other N
points. This is useful to reduce plot file size bat cannot be used (will be
ignored) with the other two gap types.

Ignore certain data file formats from consideration. Append a|c|t to ignore MGD77
ASCII, MGD77+ netCDF, or plain table files, respectively. The option may be
repeated to ignore more than one format. [Default ignores none].

-K (more ...)
Do not finalize the PostScript plot.

To put time/distance log-marks on the track. E.g. a500ka24ht6h means (a)nnotate
every 500 km (k) and 24 h(ours), with (t)ickmarks every 500 km and 6 hours.
Alternatively you may use the modifiers d (days) and n (nautical miles).

-O (more ...)
Append to existing PostScript plot.

-P (more ...)
Select "Portrait" plot orientation.

Do not plot data that are less than startdist meter along track from port of
departure. Append k for km, m for miles, or n for nautical miles [Default is 0

Do not plot data that are more than stopdist meter along track from port of
departure. Append k for km, m for miles, or n for nautical miles [Default is end of

Controls the attributes of the three kinds of markers (T for the first time marker
in a new day, t for additional time markers in the same day, and d for distance
markers). For each of these you can specify the 5 comma-separated attributes
markersize, markercolor, markerfontsize, markerfont, and markerfontcolor. Repeat
the -T option for each marker type.

-U[just/dx/dy/][c|label] (more ...)
Draw GMT time stamp logo on plot.

Append pen used for the trackline. [Defaults: width = default, color = black, style
= solid]. A leading + will use the lookup color (via -C) for both symbol fill and
outline pen color, while a leading - will set outline pen color and turn off symbol


-Y[a|c|f|r][y-shift[u]] (more ...)
Shift plot origin.

-V[level] (more ...)
Select verbosity level [c].

-ccopies (more ...)
Specify number of plot copies [Default is 1].

-p[x|y|z]azim/elev[/zlevel][+wlon0/lat0[/z0]][+vx0/y0] (more ...)
Select perspective view.

-t[transp] (more ...)
Set PDF transparency level in percent.

-^ or just -
Print a short message about the syntax of the command, then exits (NOTE: on Windows
use just -).

-+ or just +
Print an extensive usage (help) message, including the explanation of any
module-specific option (but not the GMT common options), then exits.

-? or no arguments
Print a complete usage (help) message, including the explanation of options, then

Print GMT version and exit.

Print full path to GMT share directory and exit.


To generate a Mercator plot of the track of the cruise 01010007 in the area 70W to 20E,
40S to 20N, using a Mercator scale of 0.1inch/degree, label the tracks with 10 points
characters, annotate the boundaries every 10 degrees, draw gridlines every 5 degrees, and
mark the track every day and 1000 km, with ticks every 6 hours and 250 km, and send the
plot to the default printer, enter the following command:

gmt mgd77track 01010007 -R70W/20E/40S/20N -Jm0.1 -B10g5 -A10 \
-La1da1000kf6hf250k \| lpr

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