1GRDVECTOR(1) GMT GRDVECTOR(1)
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6 grdvector - Plot vector field from two component grids
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9 grdvector compx.nc compy.nc -Jparameters [ -A ] [ -B[p|s]parameters ]
10 [ -Ccpt ] [ -Gfill ] [ -I[x]dx[/dy] ] [ -K ] [ -N ] [ -O ] [ -P
11 ] [ -Qparameters ] [ -Rregion ] [ -S[i|l]scale ] [ -T ] [
12 -U[stamp] ] [ -Wpen ] [ -Xx_offset ] [ -Yy_offset ] [ -Z ] [
13 -fflags ] [ -pflags ] [ -ttransp ]
14 Note: No space is allowed between the option flag and the associated
16 arguments.
17
19 grdvector reads two 2-D grid files which represents the x- and y-compo‐
20 nents of a vector field and produces a vector field plot by drawing
21 vectors with orientation and length according to the information in the
22 files. Alternatively, polar coordinate r, theta grids may be given
23 instead.
24
26 compx.nc
27 Contains the x-components of the vector field.
28 compy.nc
30 Contains the y-components of the vector field. (See GRID FILE
31 FORMATS below.)
32 -Jparameters (more ...)
34 Select map projection.
35
37 -A The grid files contain polar (r, theta) components instead of
38 Cartesian (x, y) [Default is Cartesian components].
39 -B[p|s]parameters (more ...)
41 Set map boundary frame and axes attributes.
42 -C[cpt]
44 Use cpt to assign colors based on vector length. Alternatively,
45 supply the name of a GMT color master dynamic CPT [rainbow] to
46 automatically determine a continuous CPT from the grid's
47 z-range. If the dynamic CPT has a default range then that range
48 will be imposed instead. Yet another option is to specify
49 -Ccolor1,color2[,color3,...] to build a linear continuous cpt
50 from those colors automatically. In this case colorn can be a
51 r/g/b triplet, a color name, or an HTML hexadecimal color (e.g.
52 #aabbcc ).
53 -Gfill Sets color or shade for vector interiors [Default is no fill].
55 -I[x]dx[/dy]
57 Only plot vectors at nodes every x_inc, y_inc apart (must be
58 multiples of original grid spacing). Append m for arc minutes or
59 s for arc seconds. Alternatively, use -Ix to specify the multi‐
60 ples multx[/multy] directly [Default plots every node].
61 -K (more ...)
63 Do not finalize the PostScript plot.
64 -N Do NOT clip vectors at map boundaries [Default will clip].
66 -O (more ...)
68 Append to existing PostScript plot.
69 -P (more ...)
71 Select "Portrait" plot orientation.
72 -Qparameters
74 Modify vector parameters. For vector heads, append vector head
75 size [Default is 0, i.e., stick-plot]. See VECTOR ATTRIBUTES for
76 specifying additional attributes.
77 -Rxmin/xmax/ymin/ymax[+r][+uunit] (more ...)
79 Specify the region of interest. Specify a subset of the grid.
80 -S[i|l]scale
82 Sets scale for Cartesian vector length in data units per dis‐
83 tance measurement unit [1]. Append c, i, or p to indicate the
84 measurement unit (cm, inch,or point). Prepend l to indicate a
85 fixed length for all vectors. For Geographic data, give scale
86 in data units per km. Use -Si if it is simpler to give the
87 reciprocal scale in measurement unit per data unit or km per
88 data unit.
89 -T Means the azimuths of Cartesian data sets should be adjusted
91 according to the signs of the scales in the x- and y-directions
92 [Leave alone]. This option can be used to convert vector
93 azimuths in cases when a negative scale is used in one of both
94 directions (e.g., positive down).
95 -U[[just]/dx/dy/][c|label] (more ...)
97 Draw GMT time stamp logo on plot.
98 -V[level] (more ...)
100 Select verbosity level [c].
101 -Wpen Set pen attributes used for vector outlines [Default: width =
103 default, color = black, style = solid].
104 -X[a|c|f|r][x-shift[u]]
106 -Y[a|c|f|r][y-shift[u]] (more ...)
108 Shift plot origin.
109 -Z The theta grid provided contains azimuths rather than directions
111 (implies -A).
112 -f[i|o]colinfo (more ...)
114 Specify data types of input and/or output columns.
115 -p[x|y|z]azim[/elev[/zlevel]][+wlon0/lat0[/z0]][+vx0/y0] (more ...)
117 Select perspective view.
118 -t[transp] (more ...)
120 Set PDF transparency level in percent.
121 -^ or just -
123 Print a short message about the syntax of the command, then
124 exits (NOTE: on Windows just use -).
125 -+ or just +
127 Print an extensive usage (help) message, including the explana‐
128 tion of any module-specific option (but not the GMT common
129 options), then exits.
130 -? or no arguments
132 Print a complete usage (help) message, including the explanation
133 of all options, then exits.
134
136 By default GMT writes out grid as single precision floats in a
137 COARDS-complaint netCDF file format. However, GMT is able to produce
138 grid files in many other commonly used grid file formats and also
139 facilitates so called "packing" of grids, writing out floating point
140 data as 1- or 2-byte integers. (more ...)
141
143 Several modifiers may be appended to the vector-producing options to
144 specify the placement of vector heads, their shapes, and the justifica‐
145 tion of the vector. Below, left and right refers to the side of the
146 vector line when viewed from the start point to the end point of the
147 segment:
148 +aangle sets the angle of the vector head apex [30].
149 +b places a vector head at the beginning of the vector path [none].
151 Optionally, append t for a terminal line, c for a circle, a for
152 arrow [Default], i for tail, A for plain arrow, and I for plain
153 tail. Further append l|r to only draw the left or right side of
154 this head [both sides].
155 +e places a vector head at the end of the vector path [none].
157 Optionally, append t for a terminal line, c for a circle, a for
158 arrow [Default], i for tail, A for plain arrow, and I for plain
159 tail. Further append l|r to only draw the left or right side of
160 this head [both sides].
161 +g-|fill turns off vector head fill (if -) or sets the vector head
163 fill [Default fill is used, which may be no fill].
164 +hshape sets the shape of the vector head (range -2/2). Default is
166 controlled by MAP_VECTOR_SHAPE [0].
167 +l draws half-arrows, using only the left side of specified heads
169 [both sides].
170 +m places a vector head at the mid-point the vector path [none].
172 Append f or r for forward or reverse direction of the vector [for‐
173 ward]. Optionally, append t for a terminal line, c for a circle, or
174 a for arrow head [Default]. Further append l|r to only draw the
175 left or right side of this head [both sides]. Cannot be combined
176 with +b or +e.
177 +nnorm scales down vector attributes (pen thickness, head size) with
179 decreasing length, where vectors shorter than norm will have their
180 attributes scaled by length/norm [arrow attributes remains invariant
181 to length].
182 +oplon/plat specifies the oblique pole for the great or small cir‐
184 cles. Only needed for great circles if +q is given.
185 +p[-][pen] sets the vector pen attributes. If pen has a leading -
187 then the head outline is not drawn. [Default pen is used, and head
188 outline is drawn]
189 +q means the input angle, length data instead represent the start
191 and stop opening angles of the arc segment relative to the given
192 point.
193 +r draws half-arrows, using only the right side of specified heads
195 [both sides].
196 +t[b|e]trim will shift the beginning or end point (or both) along
198 the vector segment by the given trim; append suitable unit. If the
199 modifiers b|e are not used then trim may be two values separated by
200 a slash, which is used to specify different trims for the two ends.
201 Positive trims will shorted the vector while negative trims will
202 lengthen it [no trim].
203 In addition, all but circular vectors may take these modifiers:
205 +jjust determines how the input x,y point relates to the vector.
206 Choose from beginning [default], end, or center.
207 +s means the input angle, length are instead the x, y coordinates of
209 the vector end point.
210 Finally, Cartesian vectors may take these modifiers:
212 +zscale[unit] expects input dx,dy vector components and uses the
213 scale to convert to polar coordinates with length in given unit.
214
216 To draw the vector field given by the files r.nc and theta.nc on a lin‐
217 ear plot with scale 5 cm per data unit, using vector rather than stick
218 plot, scale vector magnitudes so that 10 units equal 1 inch, and center
219 vectors on the node locations, run
220 gmt grdvector r.nc theta.nc -Jx5c -A -Q0.1i+e+jc -S10i > gradient.ps
222 To plot a geographic data sets given the files com_x.nc and comp_y.nc,
224 using a scale of 200 km per data unit and only plot every 3rd node in
225 either direction, try
226 gmt grdvector comp_x.nc comp_y.nc -Ix3 -JH0/20c -Q0.1i+e+jc -S200 > globe.ps
228
230 gmt, gmtcolors, grdcontour, psxy
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233 2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
2345.4.5 Feb 24, 2019 GRDVECTOR(1)