Provided by: gmt_4.5.11-1build1_amd64 bug

NAME

       grdvector - Plot vector fields from grid files

SYNOPSIS

       grdvector compx.grd compy.grd -Jparameters [ -A ] [ -B[p|s]parameters ] [ -Ccptfile ] [ -E
       ] [ -Gfill ] [ -Ixinc[unit][=|+][/yinc[unit][=|+]] ] [ -K ] [ -N  ]  [  -O  ]  [  -P  ]  [
       -Qparameters   ]   [   -Rwest/east/south/north[r]   ]   [   -S[l]scale   ]   [   -T   ]  [
       -U[just/dx/dy/][c|label] ] [ -V ] [ -Wpen  ]  [  -X[a|c|r][x-shift[u]]  ]  [  -Y[a|c|r][y-
       shift[u]] ] [ -Z ] [ -ccopies ] [ -f[i|o]colinfo ]

DESCRIPTION

       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 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.

       compx.grd
              Contains the x-component of the vector field.

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

       -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
              .gmtdefaults4, but this can be overridden on the command line by appending c, i, or
              m to the scale/width value.  When central meridian is optional, default  is  center
              of  longitude  range  on -R option.  Default standard parallel is the equator.  For
              map height, max dimension, or min dimension, append  h,  +,  or  -  to  the  width,
              respectively.
              More details can be found in the psbasemap man pages.

              CYLINDRICAL PROJECTIONS:

              -Jclon0/lat0/scale (Cassini)
              -Jcyl_stere/[lon0/[lat0/]]scale (Cylindrical Stereographic)
              -Jj[lon0/]scale (Miller)
              -Jm[lon0/[lat0/]]scale (Mercator)
              -Jmlon0/lat0/scale (Mercator - Give meridian and standard parallel)
              -Jo[a]lon0/lat0/azimuth/scale (Oblique Mercator - point and azimuth)
              -Jo[b]lon0/lat0/lon1/lat1/scale (Oblique Mercator - two points)
              -Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point and pole)
              -Jq[lon0/[lat0/]]scale (Cylindrical Equidistant)
              -Jtlon0/[lat0/]scale (TM - Transverse Mercator)
              -Juzone/scale (UTM - Universal Transverse Mercator)
              -Jy[lon0/[lat0/]]scale (Cylindrical Equal-Area)

              CONIC PROJECTIONS:

              -Jblon0/lat0/lat1/lat2/scale (Albers)
              -Jdlon0/lat0/lat1/lat2/scale (Conic Equidistant)
              -Jllon0/lat0/lat1/lat2/scale (Lambert Conic Conformal)
              -Jpoly/[lon0/[lat0/]]scale ((American) Polyconic)

              AZIMUTHAL PROJECTIONS:

              -Jalon0/lat0[/horizon]/scale (Lambert Azimuthal Equal-Area)
              -Jelon0/lat0[/horizon]/scale (Azimuthal Equidistant)
              -Jflon0/lat0[/horizon]/scale (Gnomonic)
              -Jglon0/lat0[/horizon]/scale (Orthographic)
              -Jglon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale (General Perspective).
              -Jslon0/lat0[/horizon]/scale (General Stereographic)

              MISCELLANEOUS PROJECTIONS:

              -Jh[lon0/]scale (Hammer)
              -Ji[lon0/]scale (Sinusoidal)
              -Jkf[lon0/]scale (Eckert IV)
              -Jk[s][lon0/]scale (Eckert VI)
              -Jn[lon0/]scale (Robinson)
              -Jr[lon0/]scale (Winkel Tripel)
              -Jv[lon0/]scale (Van der Grinten)
              -Jw[lon0/]scale (Mollweide)

              NON-GEOGRAPHICAL PROJECTIONS:

              -Jp[a]scale[/origin][r|z] (Polar coordinates (theta,r))
              -Jxx-scale[d|l|ppow|t|T][/y-scale[d|l|ppow|t|T]] (Linear, log, and power scaling)

OPTIONS

       No space between the option flag and the associated arguments.

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

       -B     Sets map boundary annotation and tickmark intervals; see the psbasemap man page for
              all the 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].   (See  SPECIFYING
              FILL below).

       -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].

       -O     Selects Overlay plot mode [Default initializes a new plot system].

       -P     Selects Portrait plotting mode [Default is Landscape,  see  gmtdefaults  to  change
              this].

       -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 appearance scaled by length/size.

       -R     xmin, xmax, ymin, and ymax specify the Region of interest.  For geographic regions,
              these limits correspond to west, east, south, and north and you may specify them in
              decimal degrees or in [+-]dd:mm[:ss.xxx][W|E|S|N] format.  Append r if  lower  left
              and  upper  right map coordinates are given instead of w/e/s/n.  The two shorthands
              -Rg and -Rd stand for global domain (0/360 and -180/+180 in longitude respectively,
              with  -90/+90  in  latitude).   Alternatively, specify the name of an existing grid
              file and the -R settings (and grid spacing, if  applicable)  are  copied  from  the
              grid.   For  calendar  time  coordinates  you  may  either  give  (a) relative time
              (relative to the selected TIME_EPOCH and in the selected  TIME_UNIT;  append  t  to
              -JX|x),  or  (b)  absolute time of the form [date]T[clock] (append T to -JX|x).  At
              least one of date and clock must be present; the T is always  required.   The  date
              string must be of the form [-]yyyy[-mm[-dd]] (Gregorian calendar) or yyyy[-Www[-d]]
              (ISO week calendar), while the clock string must be  of  the  form  hh:mm:ss[.xxx].
              The  use  of  delimiters  and their type and positions must be exactly as indicated
              (however, input, output  and  plot  formats  are  customizable;  see  gmtdefaults).
              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.  By adding just/dx/dy/, the user may specify
              the justification of the stamp and where the stamp should fall on the page relative
              to  lower  left  corner of the plot.  For example, BL/0/0 will align the lower left
              corner of the time stamp with the lower  left  corner  of  the  plot.   Optionally,
              append  a  label,  or  c (which will plot the command string.).  The GMT parameters
              UNIX_TIME, UNIX_TIME_POS, and UNIX_TIME_FORMAT can affect the appearance;  see  the
              gmtdefaults man page for details.  The time string will be in the locale set by the
              environment variable TZ (generally local time).

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

       -W     Set pen attributes used for vector outlines [Default: width = 0.25p, color = black,
              texture = solid].  (See SPECIFYING PENS below).

       -X -Y  Shift  plot  origin  relative  to  the  current  origin  by  (x-shift,y-shift)  and
              optionally  append  the  length  unit (c, i, m, p).  You can prepend a to shift the
              origin back to the original position after plotting, or  prepend   r  [Default]  to
              reset  the  current origin to the new location.  If -O is used then the default (x-
              shift,y-shift)  is  (0,0),  otherwise  it  is  (r1i,  r1i)   or   (r2.5c,   r2.5c).
              Alternatively,  give c to align the center coordinate (x or y) of the plot with the
              center of the page based on current page size.

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

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

       -f     Special formatting of input and/or output  columns  (time  or  geographical  data).
              Specify  i  or  o  to  make  this apply only to input or output [Default applies to
              both].  Give one or more columns (or column ranges) separated by commas.  Append  T
              (absolute calendar time), t (relative time in chosen TIME_UNIT since TIME_EPOCH), x
              (longitude), y (latitude), or f (floating point) to each  column  or  column  range
              item.  Shorthand -f[i|o]g means -f[i|o]0x,1y (geographic coordinates).

   SPECIFYING PENS
       pen    The  attributes  of  lines  and  symbol  outlines  as  defined  by  pen  is a comma
              delimetered list of width, color and texture, each of which is optional.  width can
              be   indicated   as   a   measure   (points,  centimeters,  inches)  or  as  faint,
              thin[ner|nest], thick[er|est], fat[ter|test], or obese.   color  specifies  a  gray
              shade  or  color  (see SPECIFYING COLOR below).  texture is a combination of dashes
              `-' and dots `.'.

   SPECIFYING FILL
       fill   The attribute fill specifies the solid shade or solid color (see  SPECIFYING  COLOR
              below)  or  the  pattern  used  for  filling  polygons.   Patterns are specified as
              pdpi/pattern, where pattern gives the number of the built-in pattern (1-90) or  the
              name  of  a  Sun  1-, 8-, or 24-bit raster file. The dpi sets the resolution of the
              image.  For  1-bit  rasters:  use  Pdpi/pattern  for  inverse  video,   or   append
              :Fcolor[B[color]]  to  specify  fore-  and  background  colors  (use  color = - for
              transparency).  See GMT Cookbook & Technical Reference Appendix E  for  information
              on individual patterns.

   SPECIFYING COLOR
       color  The color of lines, areas and patterns can be specified by a valid color name; by a
              gray shade (in the range 0-255); by a decimal color  code  (r/g/b,  each  in  range
              0-255;  h-s-v,  ranges  0-360,  0-1,  0-1;  or c/m/y/k, each in range 0-1); or by a
              hexadecimal color code (#rrggbb, as used in HTML).  See the gmtcolors  manpage  for
              more information and a full list of color names.

GRID FILE FORMATS

       GMT  is  able  to  recognize  many  of the commonly used grid file formats, as well as the
       precision, scale and offset of the values contained in the grid file.  When  GMT  needs  a
       little help with that, you can add the suffix =id[/scale/offset[/nan]], where id is a two-
       letter identifier of the grid type and precision, and scale and offset are optional  scale
       factor  and offset to be applied to all grid values, and nan is the value used to indicate
       missing data.  See grdreformat(1) and Section 4.17 of  the  GMT  Technical  Reference  and
       Cookbook for more information.

       When  reading  a  netCDF file that contains multiple grids, GMT will read, by default, the
       first 2-dimensional grid that can find in that file. To  coax  GMT  into  reading  another
       multi-dimensional  variable  in  the  grid  file,  append ?varname to the file name, where
       varname is the name of the variable. Note that you may need to escape the special  meaning
       of  ?  in  your  shell  program  by  putting a backslash in front of it, or by placing the
       filename and suffix between quotes or double quotes.  See grdreformat(1) and Section  4.18
       of  the  GMT Technical Reference and Cookbook for more information, particularly on how to
       read splices of 3-, 4-, or 5-dimensional grids.

EXAMPLES

       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, run

       grdvector r.grd theta.grd -Jx 5c -A -Q -S 10i > gradient.ps

SEE ALSO

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