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][n] ]


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.  Projec-
       tions  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 coor-
       dinate system is created which has its equator along that path, and the
       zero  meridian through the Center.  Then the oblique longitude (p) cor-
       responds 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  pro-
       jection 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 designa-
       tors 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  col-
              umns  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 corre-
              sponding 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  coordi-
              nate).   -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)].  Applies to
              geographic coordinates only.

       -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].

       -O     Selects Overlay plot mode [Default initializes a new  plot  sys-
              tem].


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  grd-
       track, 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  coordi-
       nates  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(l), gmt(l), mapproject(l), grdproject(l)



VERSION                              DATE                           PROJECT(l)

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