PROJECT(l)																PROJECT(l)

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 pro-
       file (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 posi-
       tion -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 pos-
       itive (q) direction is toward the pole.	To specify an oblique projection, use the -T option to set the Pole. Then the equator of the  pro-
       jection	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  projec-
       tion,  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)].  Applies to geo-
	      graphic 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].

       -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(1gmt), gmt(1gmt), mapproject(1gmt), grdproject(1gmt)

								    1 Jan 2004								PROJECT(l)