Provided by: gmt-common_5.4.3+dfsg-1_all bug


       grdvector - Plot vector field from two component grids


       grdvector  -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.


       grdvector reads two 2-D grid 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 r, theta  grids
       may be given instead.

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

       -Jparameters (more …)
              Select map projection.


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

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

              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 grid’s 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,…] 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].

              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 multiples multx[/multy] directly [Default plots every node].

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

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

       -O (more …)
              Append to existing PostScript plot.

       -P (more …)
              Select “Portrait” plot orientation.

              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 …)
              Specify the region of interest. Specify a subset of the grid.

              Sets  scale for Cartesian vector length in data units per distance 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 …)
              Draw GMT time stamp logo on plot.

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

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


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

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

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

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

       -t[transp] (more …)
              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  explanation  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.


       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 “packing” of grids, writing out floating point
       data as 1- or 2-byte integers. (more …)


       Several modifiers may be appended to the vector-producing options to specify the placement
       of vector heads, their shapes, and the justification 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 [forward].  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 circles.  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

       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.


       To draw the vector field given by the files and on a linear 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 -Jx5c -A -Q0.1i+e+jc -S10i >

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

              gmt grdvector -Ix3 -JH0/20c -Q0.1i+e+jc -S200 >


       gmt, gmtcolors, grdcontour, psxy


       2018, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe