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project(1)                            GMT                           project(1)




NAME

       project  -  Project  table  data  onto lines or great circles, generate
       tracks, or translate coordinates


SYNOPSIS

       project [ table ]  -Ccx/cy [  -Aazimuth ] [  -Ebx/by ] [  -Fflags  ]  [
       -Gdist[/colat][+h]  ] [  -L[w][l_min/l_max] ] [  -N ] [  -Q ] [  -S ] [
       -Tpx/py ] [  -V[level] ] [  -Ww_min/w_max ] [ -bbinary ] [ -dnodata ] [
       -eregexp ] [ -fflags ] [ -ggaps ] [ -hheaders ] [ -iflags ] [ -sflags ]
       [ -:[i|o] ]

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


DESCRIPTION

       project reads arbitrary (x, y[,z]) data from standard input [or table ]
       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 posi-
       tion 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 coor-
       dinate system is created which has its equator along that path, and the
       zero meridian through the Center. Then the oblique longitude (p) corre-
       sponds  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.

       Calculations of specific great-circle and  geodesic  distances  or  for
       back-azimuths or azimuths are better done using mapproject.

       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.


REQUIRED ARGUMENTS

       -Ccx/cy
              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.  The cx/cy is not required to be 90 degrees from the pole.


OPTIONAL ARGUMENTS

       table  One  or  more ASCII (or binary, see -bi[ncols][type]) data table
              file(s) holding a number of data columns. If no tables are given
              then we read from standard input.

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

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

       -Fflags
              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, see -bo) columns of values cor-
              responding  to  xyzpqrs  [Default]. 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.

       -Gdist[/colat][+h]
              Generate  mode. No input is read. Create (r, s, p) output points
              every dist units of p.  See  -Q  option.  Alternatively,  append
              /colat  for  a  small circle instead [Default is a colatitude of
              90, i.e., a great circle]. Use -C and -E to  generate  a  circle
              that  goes  through the center and end point. Note, in this case
              the center and end point cannot be farther apart than 2*|colat|.
              Finally, if you append +h the we will report the position of the
              pole as part of the segment header [no header].

       -L[w][l_min/l_max]
              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.

       -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 to be in the same units.

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

       -Tpx/py
              px/py sets the position of the rotation pole of the  projection.
              (Definition 3).

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

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

       -bi[ncols][t] (more a|)
              Select native binary input. [Default is 2 input columns].

       -bo[ncols][type] (more a|)
              Select native binary output. [Default is given by -F or -G].

       -d[i|o]nodata (more a|)
              Replace input columns that equal nodata  with  NaN  and  do  the
              reverse on output.

       -e[~]^<i>apattern^<i>a | -e[~]/regexp/[i] (more a|)
              Only accept data records that match the given pattern.

       -f[i|o]colinfo (more a|)
              Specify data types of input and/or output columns.

       -g[a]x|y|d|X|Y|D|[col]z[+|-]gap[u] (more a|)
              Determine data gaps and line breaks.

       -h[i|o][n][+c][+d][+rremark][+rtitle] (more a|)
              Skip or produce header record(s).

       -icols[+l][+sscale][+ooffset][,^<i>a|] (more a|)
              Select input columns and transformations (0 is first column).

       -s[cols][a|r] (more a|)
              Set handling of NaN records.

       -:[i|o] (more a|)
              Swap 1st and 2nd column on input and/or output.

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

       -+ or just +
              Print an extensive usage (help) message, including the  explana-
              tion  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 all options, then exits.


ASCII FORMAT PRECISION

       The ASCII output formats of numerical data are controlled by parameters
       in your gmt.conf file. Longitude and latitude are  formatted  according
       to   FORMAT_GEO_OUT,  absolute  time  is  under  the  control  of  FOR-
       MAT_DATE_OUT and FORMAT_CLOCK_OUT, whereas general floating point  val-
       ues are formatted according to FORMAT_FLOAT_OUT. Be aware that the for-
       mat in effect can lead to loss of precision in ASCII output, which  can
       lead  to  various  problems  downstream.  If you find the output is not
       written with enough precision, consider switching to binary output (-bo
       if  available) or specify more decimals using the FORMAT_FLOAT_OUT set-
       ting.


EXAMPLES

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

              gmt 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 generate points every 1 degree along a  great  circle  from  30N,10W
       with azimuth 30 and covering a full 360, try:

              gmt project -C10W/30N -A30 -G1 -L-180/180 > great_circle.txt

       To  generate  points  every  10km along a small circle of colatitude 60
       from 10N,50W to 30N,10W:

              gmt project -C-50/10 -E-10/30 -G10/60 -Q > small_circle_points.xyp

       To create a partial small circle of  colatitude  80  about  a  pole  at
       40E,85N,  with  extent  of  45  degrees  to either side of the meridian
       defined by the great circle from the pole to a point 15E,15N, try

              gmt project -C15/15 -T40/85 -G1/80 -L-45/45 > some_circle.xyp

       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, run:

              gmt 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, use:

              gmt 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, run:

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

       Suppose that pacific_topo.nc is a grid file of bathymetry, and you want
       to make a file of flowlines in the hotspot reference frame. If you run:

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

       then flow.nc is a file in the same area as  pacific_topo.nc,  but  flow
       contains  the  latitudes  about the pole of the projection. You now can
       use grdcontour on flow.nc 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(1), gmt(1), gmtvector(1), grdtrack(1), mapproject(1),
       grdproject(1), grdtrack(1)


COPYRIGHT

       2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe



5.4.2                            Jun 24, 2017                       project(1)

gmt5 5.4.2 - Generated Thu Jun 29 15:01:04 CDT 2017
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