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grdvector(1)                          GMT                         grdvector(1)




NAME

       grdvector - Plot vector field from two component grids


SYNOPSIS

       grdvector compx.nc compy.nc -Jparameters [  -A ] [  -B[p|s]parameters ]
       [  -Ccpt ] [  -Gfill ] [  -I[x]dx[/dy] ] [  -K ] [  -N ] [  -O ] [   -P
       ]  [   -Qparameters  ]  [   -Rregion  ]  [   -S[i|l]scale  ]  [  -T ] [
       -U[stamp] ] [  -Wpen ] [  -Xx_offset ]  [   -Yy_offset  ]  [   -Z  ]  [
       -fflags ] [ -pflags ] [ -ttransp ]

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


DESCRIPTION

       grdvector reads two 2-D grid files which represents the x- and y-compo-
       nents  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  r,  theta grids may be given
       instead.


REQUIRED ARGUMENTS

       compx.nc
              Contains the x-components of the vector field.

       compy.nc
              Contains the y-components of the vector field.  (See  GRID  FILE
              FORMATS below.)

       -Jparameters (more a|)
              Select map projection.


OPTIONAL ARGUMENTS

       -A     The  grid  files  contain polar (r, theta) components instead of
              Cartesian (x, y) [Default is Cartesian components].

       -B[p|s]parameters (more a|)
              Set map boundary frame and axes attributes.

       -C[cpt]
              Use cpt to assign colors based on vector length.  Alternatively,
              supply  the  name of a GMT color master dynamic CPT [rainbow] to
              automatically  determine  a  continuous  CPT  from  the   gridas
              z-range.  If the dynamic CPT has a default range then that range
              will be imposed instead.   Yet  another  option  is  to  specify
              -Ccolor1,color2[,color3,a|]  to  build  a  linear continuous cpt
              from those colors automatically.  In this case colorn can  be  a
              r/g/b  triplet, a color name, or an HTML hexadecimal color (e.g.
              #aabbcc ).

       -Gfill Sets color or shade for vector interiors [Default is no fill].

       -I[x]dx[/dy]
              Only plot vectors at nodes every x_inc,  y_inc  apart  (must  be
              multiples of original grid spacing). Append m for arc minutes or
              s for arc seconds.  Alternatively, use -Ix to specify the multi-
              ples multx[/multy] directly [Default plots every node].

       -K (more a|)
              Do not finalize the PostScript plot.

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

       -O (more a|)
              Append to existing PostScript plot.

       -P (more a|)
              Select aPortraita plot orientation.

       -Qparameters
              Modify  vector  parameters. For vector heads, append vector head
              size [Default is 0, i.e., stick-plot]. See VECTOR ATTRIBUTES for
              specifying additional attributes.

       -Rxmin/xmax/ymin/ymax[+r][+uunit] (more a|)
              Specify the region of interest. Specify a subset of the grid.

       -S[i|l]scale
              Sets  scale  for  Cartesian vector length in data units per dis-
              tance measurement unit [1]. Append c, i, or p  to  indicate  the
              measurement  unit  (cm,  inch,or point). Prepend l to indicate a
              fixed length for all vectors.  For Geographic data,  give  scale
              in  data  units  per  km.  Use  -Si if it is simpler to give the
              reciprocal scale in measurement unit per data  unit  or  km  per
              data unit.

       -T     Means  the  azimuths  of  Cartesian data sets should be adjusted
              according to the signs of the scales in the x- and  y-directions
              [Leave  alone].   This  option  can  be  used  to convert vector
              azimuths in cases when a negative scale is used in one  of  both
              directions (e.g., positive down).

       -U[[just]/dx/dy/][c|label] (more a|)
              Draw GMT time stamp logo on plot.

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

       -Wpen  Set  pen  attributes  used for vector outlines [Default: width =
              default, color = black, style = solid].

       -X[a|c|f|r][x-shift[u]]

       -Y[a|c|f|r][y-shift[u]] (more a|)
              Shift plot origin.

       -Z     The theta grid provided contains azimuths rather than directions
              (implies -A).

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

       -p[x|y|z]azim[/elev[/zlevel]][+wlon0/lat0[/z0]][+vx0/y0] (more a|)
              Select perspective view.

       -t[transp] (more a|)
              Set PDF transparency level in percent.

       -^ 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.


GRID FILE FORMATS

       By  default  GMT  writes  out  grid  as  single  precision  floats in a
       COARDS-complaint netCDF file format. However, GMT is  able  to  produce
       grid  files  in  many  other  commonly  used grid file formats and also
       facilitates so called apackinga of grids, writing  out  floating  point
       data as 1- or 2-byte integers. (more a|)


VECTOR ATTRIBUTES

       Several  modifiers  may  be appended to the vector-producing options to
       specify the placement of vector heads, their shapes, and the justifica-
       tion  of  the  vector.  Below, left and right refers to the side of the
       vector line when viewed from the start point to the end  point  of  the
       segment:
          +aangle sets the angle of the vector head apex [30].

          +b  places a vector head at the beginning of the vector path [none].
          Optionally, append t for a terminal line, c  for  a  circle,  a  for
          arrow  [Default],  i  for  tail,  A for plain arrow, and I for plain
          tail.  Further append l|r to only draw the left  or  right  side  of
          this head [both sides].

          +e  places  a  vector  head  at  the  end of the vector path [none].
          Optionally, append t for a terminal line, c  for  a  circle,  a  for
          arrow  [Default],  i  for  tail,  A for plain arrow, and I for plain
          tail.  Further append l|r to only draw the left  or  right  side  of
          this head [both sides].

          +g-|fill  turns  off vector head fill (if -) or sets the vector head
          fill [Default fill is used, which may be no fill].

          +hshape sets the shape of the vector head (range -2/2).  Default  is
          controlled by MAP_VECTOR_SHAPE [0].

          +l  draws  half-arrows,  using only the left side of specified heads
          [both sides].

          +m places a vector head at the mid-point  the  vector  path  [none].
          Append  f  or r for forward or reverse direction of the vector [for-
          ward].  Optionally, append t for a terminal line, c for a circle, or
          a  for  arrow  head  [Default].  Further append l|r to only draw the
          left or right side of this head [both sides].   Cannot  be  combined
          with +b or +e.

          +nnorm scales down vector attributes (pen thickness, head size) with
          decreasing length, where vectors shorter than norm will  have  their
          attributes scaled by length/norm [arrow attributes remains invariant
          to length].

          +oplon/plat specifies the oblique pole for the great or  small  cir-
          cles.  Only needed for great circles if +q is given.

          +p[-][pen]  sets  the  vector pen attributes. If pen has a leading -
          then the head outline is not drawn. [Default pen is used,  and  head
          outline is drawn]

          +q  means  the  input angle, length data instead represent the start
          and stop opening angles of the arc segment  relative  to  the  given
          point.

          +r  draws  half-arrows, using only the right side of specified heads
          [both sides].

          +t[b|e]trim will shift the beginning or end point  (or  both)  along
          the  vector  segment by the given trim; append suitable unit. If the
          modifiers b|e are not used then trim may be two values separated  by
          a  slash, which is used to specify different trims for the two ends.
          Positive trims will shorted the vector  while  negative  trims  will
          lengthen it [no trim].

       In addition, all but circular vectors may take these modifiers:
          +jjust  determines  how  the  input x,y point relates to the vector.
          Choose from beginning [default], end, or center.

          +s means the input angle, length are instead the x, y coordinates of
          the vector end point.

       Finally, Cartesian vectors may take these modifiers:
          +zscale[unit]  expects  input  dx,dy  vector components and uses the
          scale to convert to polar coordinates with length in given unit.


EXAMPLES

       To draw the vector field given by the files r.nc and theta.nc on a lin-
       ear  plot with scale 5 cm per data unit, using vector rather than stick
       plot, scale vector magnitudes so that 10 units equal 1 inch, and center
       vectors on the node locations, run

              gmt grdvector r.nc theta.nc -Jx5c -A -Q0.1i+e+jc -S10i > gradient.ps

       To  plot a geographic data sets given the files com_x.nc and comp_y.nc,
       using a scale of 200 km per data unit and only plot every 3rd  node  in
       either direction, try

              gmt grdvector comp_x.nc comp_y.nc -Ix3 -JH0/20c -Q0.1i+e+jc -S200 > globe.ps


SEE ALSO

       gmt(1), gmtcolors(5), grdcontour(1), psxy(1)


COPYRIGHT

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



5.4.2                            Jun 24, 2017                     grdvector(1)

gmt5 5.4.2 - Generated Thu Jun 29 08:31:47 CDT 2017
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