NAME

      project - project data along a line or great circle, generate a
      profile track, or translate coordinates.

SYNOPSIS

      project [ infile ] -Fflags -Ccx/cy [ -Aazimuth ] [ -Dd|g ] [ -Ebx/by ]
      [ -Gdist ] [ -H[nrec] ] [ -L[w][l_min/l_max] ] [ -M[flag] ] [ -N ] [ -Q
      ] [ -S ] [ -Tpx/py ] [ -V ] [ -Ww_min/w_max ] [ -: ] [ -bi[s][n] ] [
      -bo[s] ]

DESCRIPTION

      project reads arbitrary (x, y[, z]) data from standard input [or
      infile ] and writes to standard output any combination of (x, y, z, p,
      q, r, s), where (p, q) are the coordinates in the projection, (r, s)
      is the position in the (x, y) coordinate system of the point on the
      profile (q = 0 path) closest to (x, y), and z is all remaining columns
      in the input (beyond the required x and y columns).  Alternatively,
      project may be used to generate (r, s, p) triples at equal increments
      dist along a profile.  In this case ( -G option), no input is read.
      Projections are defined in any (but only) one of three ways:
      (Definition 1)  By a Center -C and an Azimuth -A in degrees clockwise
      from North.  (Definition 2)  By a Center -C and end point E of the
      projection path -E.  (Definition 3)  By a Center -C and a roTation
      pole position -T.  To spherically project data along a great circle
      path, an oblique coordinate system is created which has its equator
      along that path, and the zero meridian through the Center.  Then the
      oblique longitude (p) corresponds to the distance from the Center
      along the great circle, and the oblique latitude (q) corresponds to
      the distance perpendicular to the great circle path.  When moving in
      the increasing (p) direction, (toward B or in the azimuth direction),
      the positive (q) direction is to your left.  If a Pole has been
      specified, then the positive (q) direction is toward the pole.  To
      specify an oblique projection, use the -T option to set the Pole.
      Then the equator of the projection is already determined and the -C
      option is used to locate the p = 0 meridian.  The Center cx/cy will be
      taken as a point through which the p = 0 meridian passes.  If you do
      not care to choose a particular point, use the South pole (ox = 0, oy
      = -90).  Data can be selectively windowed by using the -L and -W
      options.  If -W is used, the projection Width is set to use only
      points with w_min < q < w_max.  If -L is set, then the Length is set
      to use only those points with l_min < p < l_max.  If the -E option has
      been used to define the projection, then -Lw may be selected to window
      the length of the projection to exactly the span from O to B.  Flat
      earth (cartesian) coordinate transformations can also be made.  Set -N
      and remember that azimuth is clockwise from North (the y axis), NOT
      the usual cartesian theta, which is counterclockwise from the x axis.
      azimuth = 90 - theta.  No assumptions are made regarding the units for
      x, y, r, s, p, q, dist, l_min,l _max, w_min, w_max.  If -Q is
      selected, map units are assumed and x, y, r, s must be in degrees and
      p, q, dist, l_min, l_max, w_min, w_max will be in km.  project is CASE
      SENSITIVE.  Use UPPER CASE for all one-letter designators which begin
      optional arguments.  Use lower case for the xyzpqrs letters in -flags.


      -C   cx/cy sets the origin of the projection, in Definition 1 or 2.
           If Definition 3 is used (-T), then cx/cy are the coordinates of a
           point through which the oblique zero meridian (p = 0) should
           pass.

OPTIONS

      infile
           name of ASCII (or binary, see -bi) file(s) with 2 or more columns
           holding (x,y,[z]) data values.  If no filenames are given,
           project will read from standard input.  If the -G option is
           selected, no input data are read.

      -F   Specify your desired output using any combination of xyzpqrs, in
           any order.  Do not space between the letters.  Use lower case.
           The output will be ASCII (or binary) columns of values
           corresponding to xyzpqrs.  If both input and output are using
           ASCII format then the z data are treated as textstring(s).  If
           the -G option is selected, the output will be rsp.

      -A   azimuth defines the azimuth of the projection (Definition 1).

      -D   Set the location of the Discontinuity in longitude (r
           coordinate).  -Dd will place the discontinuity at the Dateline,
           (-180 < r < 180); -Dg will place it at Greenwich, (0 < r < 360).
           Default usually falls at dateline due to atan2 calls.

      -E   bx/by defines the end point of the projection path (Definition
           2).

      -G   dist Generate mode.  No input is read.  Create (r, s, p) output
           points every dist units of p.  See -Q option.

      -H   Input file(s) has Header record(s).  Number of header records can
           be changed by editing your .gmtdefaults file.  If used, GMT
           default is 1 header record.

      -L   Length controls.  Project only those points whose p coordinate is
           within l_min < p < l_max.  If -E has been set, then you may use
           -Lw to stay within the distance from C to E.

      -M   Multiple segment file(s).  Segments are separated by a special
           record.  For ASCII files the first character must be flag
           [Default is '>'].  For binary files all fields must be NaN.

      -N   Flat earth.  Make a cartesian coordinate transformation in the
           plane.  [Default uses spherical trigonometry.]


      -Q   Map type units, i.e., project assumes x, y, r, s are in degrees
           while p, q, dist, l_min,l _max, w_min, w_max are in km.  If -Q is
           not set, then all these are assumed in same units.

      -S   Sort the output into increasing p order.  Useful when projecting
           random data into a sequential profile.

      -T   px/py sets the position of the roTation pole of the projection.
           (Definition 3).

      -V   Selects verbose mode, which will send progress reports to stderr
           [Default runs "silently"].

      -W   Width controls.  Project only those points whose q coordinate is
           within w_min < q < w_max.

      -:   Toggles between (longitude,latitude) and (latitude,longitude)
           input/output.  [Default is (longitude,latitude)].

      -bi  Selects binary input.  Append s for single precision [Default is
           double].  Append n for the number of columns in the binary
           file(s).  [Default is 2 input columns].

      -bo  Selects binary output.  Append s for single precision [Default is
           double].

EXAMPLES

      To generate points every 10km along a great circle from 10N,50W to
      30N,10W, try:

      project -C-50/10 -E-10/30 -G10 -Q > great_circle_points.xyp

      (Note that great_circle_points.xyp could now be used as input for
      grdtrack, etc. ).

      To project the shiptrack gravity, magnetics, and bathymetry in
      c2610.xygmb along a great circle through an origin at 30S, 30W, the
      great circle having an azimuth of N20W at the origin, keeping only the
      data from NE of the profile and within +/- 500 km of the origin, try:

      project c2610.xygmb -C-30/-30 -A-20 -W-10000/0 -L-500/500 -Fpz -Q >
      c2610_projected.pgmb

      (Note in this example that -W-10000/0 is used to admit any value with
      a large negative q coordinate.  This will take those points which are
      on our right as we walk along the great circle path, or to the NE in
      this example.)

      To make a cartesian coordinate transformation of mydata.xy so that the
      new origin is at 5,3 and the new x axis (p) makes an angle of 20
      degrees with the old x axis, try:
      project mydata.xy -C5/3 -A70 -Fpq > mydata.pq

      To take data in the file pacific.lonlat and transform it into oblique
      coordinates using a pole from the hotspot reference frame and placing
      the oblique zero meridian (p = 0 line) through Tahiti, try:

      project pacific.lonlat -T-75/68 -C-149:26/-17:37 -Fpq > pacific.pq

      Suppose that pacific_topo.grd is a grdfile of bathymetry, and you want
      to make a file of flowlines in the hotspot reference frame.  If you
      try:

      grd2xyz pacific_topo.grd | project -T-75/68 -C0/-90 -Fxyq | xyz2grd
      -Retc -Ietc -Cflow.grd

      then flow.grd is a file in the same area as pacific_topo.grd, but flow
      contains the latitudes about the pole of the projection.  You now can
      use grdcontour on flow.grd to draw lines of constant oblique latitude,
      which are flow lines in the hotspot frame.

      If you have an arbitrarily rotation pole px/py and you would like to
      draw an oblique small circle on a map, you will first need to make a
      file with the oblique coordinates for the small circle (i.e., lon =
      0-360, lat is constant), then create a file with two records: the
      north pole (0/90) and the origin (0/0), and find what their oblique
      coordinates are using your rotation pole.  Now, use the projected
      North pole and origin coordinates as the rotation pole and center,
      respectively, and project your file as in the pacific example above.
      This gives coordinates for an oblique small circle.

SEE ALSO

      fitcircle, gmt, mapproject, grdproject