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       grdvector - Plot vector fields from grdfiles


       grdvector  compx.grd  compy.grd  -Jparameters [ -A ] [ -Btickinfo ] [ -Ccptfile ] [ -E ] [
       -Gfill] [ -Ix_inc[m|c][/y_inc[m|c]] ] [ -K ] [ -N ] [ -O ] [  -P  ]  [  -Qparameters  ]  [
       -Rwest/east/south/north[r]  ]  [  -S[l]scale  ]  [  -T  ]  [ -U[/dx/dy/][label] ] [ -V ] [
       -Wcontourpen ] [ -Xx-shift ] [ -Yy-shift ] [ -Z ] [ -ccopies ]


       grdvector reads two 2-D gridded files which represents the x- and y-components of a vector
       field  and  produces  a  vector  field plot by drawing vectors with orientation and length
       according to the information in the files. Alternatively, polar coordinate components  may
       be  used (r, theta).  grdvector is basically a short-hand for using 2 calls to grd2xyz and
       pasting the output through psxy -SV.

              Contains the x-component of the vector field.

              Contains the y-component of the vector field.

       -J     Selects the map projection. Scale is UNIT/degree, 1:xxxxx, or width in UNIT  (upper
              case  modifier).   UNIT is cm, inch, or m, depending on the MEASURE_UNIT setting in
              .gmtdefaults, but this can be overridden on the command line by appending the c, i,
              or m to the scale/width value.


              -Jclon0/lat0/scale (Cassini)
              -Jjlon0/scale (Miller)
              -Jmscale (Mercator - Greenwich and Equator as origin)
              -Jmlon0/lat0/scale (Mercator - Give meridian and standard parallel)
              -Joalon0/lat0/azimuth/scale (Oblique Mercator - point and azimuth)
              -Joblon0/lat0/lon1/lat1/scale (Oblique Mercator - two points)
              -Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point and pole)
              -Jqlon0/scale (Equidistant Cylindrical Projection (Plate Carree))
              -Jtlon0/scale (TM - Transverse Mercator, with Equator as y = 0)
              -Jtlon0/lat0/scale (TM - Transverse Mercator, set origin)
              -Juzone/scale (UTM - Universal Transverse Mercator)
              -Jylon0/lats/scale (Basic Cylindrical Projection)


              -Jalon0/lat0/scale (Lambert).
              -Jelon0/lat0/scale (Equidistant).
              -Jflon0/lat0/horizon/scale (Gnomonic).
              -Jglon0/lat0/scale (Orthographic).
              -Jslon0/lat0/[slat/]scale (General Stereographic)

              CONIC PROJECTIONS:

              -Jblon0/lat0/lat1/lat2/scale (Albers)
              -Jdlon0/lat0/lat1/lat2/scale (Equidistant)
              -Jllon0/lat0/lat1/lat2/scale (Lambert)


              -Jhlon0/scale (Hammer)
              -Jilon0/scale (Sinusoidal)
              -Jk[f|s]lon0/scale (Eckert IV (f) and VI (s))
              -Jnlon0/scale (Robinson)
              -Jrlon0/scale (Winkel Tripel)
              -Jvlon0/scale (Van der Grinten)
              -Jwlon0/scale (Mollweide)


              -Jp[a]scale[/origin]  (polar  (theta,r)  coordinates,  optional  a for azimuths and
              offset theta [0])
              -Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log, and power scaling)
              More details can be found in the psbasemap manpages.


       No space between the option flag and the associated arguments.

       -A     Means grdfiles have polar (r, theta) components instead of Cartesian (x, y).

       -B     Sets map boundary tickmark intervals. See psbasemap for details.

       -C     Use cptfile to assign colors based on vector length.

       -E     Center vectors on grid nodes [Default draws from grid node].

       -G     Sets color or shade for vector interiors [Default is no fill].  Specify  the  shade
              (0-255) or color (r/g/b, each in 0-255).

       -I     Only  plot vectors at nodes every x_inc, y_inc apart (must be multiples of original
              grid spacing). Append m for minutes or c for seconds. [Default plots every node].

       -K     More PostScript code will be appended later [Default terminates the plot system].

       -N     Do NOT clip vectors at map boundaries [Default will clip].

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

       -P     Selects Portrait plotting mode [GMT Default is Landscape, see gmtdefaults to change

       -Q     Select  vector  plot  [Default is stick-plot]. Optionally, specify parameters which
              are   arrowwidth/headlength/headwidth    [Default    is    0.075c/0.3c/0.25c    (or
              0.03i/0.12i/0.1i)]. Append nsize which will cause vectors shorter than size to have
              their appearence scaled by length/size.

       -R     west, east, south, and north specify the Region of interest. To specify  boundaries
              in  degrees and minutes [and seconds], use the dd:mm[:ss] format. Append r if lower
              left and upper right map coordinates are given instead of wesn.  Specify  a  subset
              of the grid.

       -S     Sets  scale  for  vector  length  in  data units per distance measurement unit [1].
              Append c, i, m, p to indicate the measurement unit (cm, inch, m, point). Prepend  l
              to indicate a fixed length for all vectors.

       -T     Means azimuth should be converted to angles based on the selected map projection.

       -U     Draw  Unix  System time stamp on plot. User may specify where the lower left corner
              of the stamp should fall on the  page  relative  to  lower  left  corner  of  plot.
              Optionally,  append  a  label,  or c (which will plot the command string.). The GMT
              parameters  UNIX_TIME  and  UNIX_TIME_POS  can  affect  the  appearance;  see   the
              gmtdefaults man page for details.

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

       -W     Set pen attributes used for vector outlines [Default: width =  1,  color  =  0/0/0,
              texture = solid].

       -X -Y  Shift origin of plot by (x-shift,y-shift).  Prepend a for absolute coordinates; the
              default (r) will reset plot origin.

       -Z     Means the angles provided are azimuths rather than direction (requires -A).

       -c     Specifies the number of plot copies. [Default is 1]


       To draw the vector field given by the files r.grd and theta.grd  on  a  linear  plot  with
       scale 5 cm per data unit, using vector rather than stick plot, and scale vector magnitudes
       so that 10 units equal 1 inch, try

       grdvector r.grd theta.grd -Jx5c -Q -S10i >


       gmt(1gmt), grdcontour(1gmt), psxy(1gmt)

                                            1 Jan 2004                               GRDVECTOR(l)