1GRDVECTOR(1) Generic Mapping Tools GRDVECTOR(1)
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6 grdvector - Plot vector fields from grid files
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9 grdvector compx.grd compy.grd -Jparameters [ -A ] [ -B[p|s]parameters ]
10 [ -Ccptfile ] [ -E ] [ -Gfill] [ -Ixinc[unit][=|+][/yinc[unit][=|+]] ]
11 [ -K ] [ -N ] [ -O ] [ -P ] [ -Qparameters ] [
12 -Rwest/east/south/north[r] ] [ -S[l]scale ] [ -T ] [
13 -U[just/dx/dy/][c|label] ] [ -V ] [ -Wpen ] [ -X[a|c|r][x-shift[u]] ] [
14 -Y[a|c|r][y-shift[u]] ] [ -Z ] [ -ccopies ] [ -f[i|o]colinfo ]
15
17 grdvector reads two 2-D gridded files which represents the x- and y-
18 components of a vector field and produces a vector field plot by draw‐
19 ing vectors with orientation and length according to the information in
20 the files. Alternatively, polar coordinate components may be used (r,
21 theta). grdvector is basically a short-hand for using 2 calls to
22 grd2xyz and pasting the output through psxy -SV.
23 compx.grd
25 Contains the x-component of the vector field.
26 compy.grd
28 Contains the y-component of the vector field. (See GRID FILE
29 FORMATS below.)
30 -J Selects the map projection. Scale is UNIT/degree, 1:xxxxx, or
32 width in UNIT (upper case modifier). UNIT is cm, inch, or m,
33 depending on the MEASURE_UNIT setting in .gmtdefaults4, but this
34 can be overridden on the command line by appending c, i, or m to
35 the scale/width value. When central meridian is optional,
36 default is center of longitude range on -R option. Default
37 standard parallel is the equator. For map height, max dimen‐
38 sion, or min dimension, append h, +, or - to the width, respec‐
39 tively.
40 More details can be found in the psbasemap man pages.
41 CYLINDRICAL PROJECTIONS:
43 -Jclon0/lat0/scale (Cassini)
45 -Jcyl_stere/[lon0/[lat0/]]scale (Cylindrical Stereographic)
46 -Jj[lon0/]scale (Miller)
47 -Jm[lon0/[lat0/]]scale (Mercator)
48 -Jmlon0/lat0/scale (Mercator - Give meridian and standard paral‐
49 lel)
50 -Jo[a]lon0/lat0/azimuth/scale (Oblique Mercator - point and
51 azimuth)
52 -Jo[b]lon0/lat0/lon1/lat1/scale (Oblique Mercator - two points)
53 -Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point and
54 pole)
55 -Jq[lon0/[lat0/]]scale (Cylindrical Equidistant)
56 -Jtlon0/[lat0/]scale (TM - Transverse Mercator)
57 -Juzone/scale (UTM - Universal Transverse Mercator)
58 -Jy[lon0/[lat0/]]scale (Cylindrical Equal-Area)
59 CONIC PROJECTIONS:
61 -Jblon0/lat0/lat1/lat2/scale (Albers)
63 -Jdlon0/lat0/lat1/lat2/scale (Conic Equidistant)
64 -Jllon0/lat0/lat1/lat2/scale (Lambert Conic Conformal)
65 AZIMUTHAL PROJECTIONS:
67 -Jalon0/lat0[/horizon]/scale (Lambert Azimuthal Equal-Area)
69 -Jelon0/lat0[/horizon]/scale (Azimuthal Equidistant)
70 -Jflon0/lat0[/horizon]/scale (Gnomonic)
71 -Jglon0/lat0[/horizon]/scale (Orthographic)
72 -Jglon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale
73 (General Perspective).
74 -Jslon0/lat0[/horizon][/slat]/scale (General Stereographic)
75 MISCELLANEOUS PROJECTIONS:
77 -Jh[lon0/]scale (Hammer)
79 -Ji[lon0/]scale (Sinusoidal)
80 -Jkf[lon0/]scale (Eckert IV)
81 -Jk[s][lon0/]scale (Eckert IV)
82 -Jn[lon0/]scale (Robinson)
83 -Jr[lon0/]scale (Winkel Tripel)
84 -Jv[lon0/]scale (Van der Grinten)
85 -Jw[lon0/]scale (Mollweide)
86 NON-GEOGRAPHICAL PROJECTIONS:
88 -Jp[a]scale[/origin][r|z] (Polar coordinates (theta,r))
90 -Jxx-scale[d|l|ppow|t|T][/y-scale[d|l|ppow|t|T]] (Linear, log,
91 and power scaling)
92
94 No space between the option flag and the associated arguments.
95 -A Means grid files have polar (r, theta) components instead of
97 Cartesian (x, y).
98 -B Sets map boundary annotation and tickmark intervals; see the
100 psbasemap man page for all the details.
101 -C Use cptfile to assign colors based on vector length.
103 -E Center vectors on grid nodes [Default draws from grid node].
105 -G Sets color or shade for vector interiors [Default is no fill].
107 (See SPECIFYING FILL below).
108 -I Only plot vectors at nodes every x_inc, y_inc apart (must be
110 multiples of original grid spacing). Append m for minutes or c
111 for seconds. [Default plots every node].
112 -K More PostScript code will be appended later [Default terminates
114 the plot system].
115 -N Do NOT clip vectors at map boundaries [Default will clip].
117 -O Selects Overlay plot mode [Default initializes a new plot sys‐
119 tem].
120 -P Selects Portrait plotting mode [Default is Landscape, see gmtde‐
122 faults to change this].
123 -Q Select vector plot [Default is stick-plot]. Optionally, specify
125 parameters which are arrowwidth/headlength/headwidth [Default is
126 0.075c/0.3c/0.25c (or 0.03i/0.12i/0.1i)]. Append nsize which
127 will cause vectors shorter than size to have their appearance
128 scaled by length/size.
129 -R xmin, xmax, ymin, and ymax specify the Region of interest. For
131 geographic regions, these limits correspond to west, east,
132 south, and north and you may specify them in decimal degrees or
133 in [+-]dd:mm[:ss.xxx][W|E|S|N] format. Append r if lower left
134 and upper right map coordinates are given instead of w/e/s/n.
135 The two shorthands -Rg and -Rd stand for global domain (0/360
136 and -180/+180 in longitude respectively, with -90/+90 in lati‐
137 tude). For calendar time coordinates you may either give (a)
138 relative time (relative to the selected TIME_EPOCH and in the
139 selected TIME_UNIT; append t to -JX|x), or (b) absolute time of
140 the form [date]T[clock] (append T to -JX|x). At least one of
141 date and clock must be present; the T is always required. The
142 date string must be of the form [-]yyyy[-mm[-dd]] (Gregorian
143 calendar) or yyyy[-Www[-d]] (ISO week calendar), while the clock
144 string must be of the form hh:mm:ss[.xxx]. The use of delim‐
145 iters and their type and positions must be exactly as indicated
146 (however, input, output and plot formats are customizable; see
147 gmtdefaults). Specify a subset of the grid.
148 -S Sets scale for vector length in data units per distance measure‐
150 ment unit [1]. Append c, i, m, p to indicate the measurement
151 unit (cm, inch, m, point). Prepend l to indicate a fixed length
152 for all vectors.
153 -T Means azimuth should be converted to angles based on the
155 selected map projection.
156 -U Draw Unix System time stamp on plot. By adding just/dx/dy/, the
158 user may specify the justification of the stamp and where the
159 stamp should fall on the page relative to lower left corner of
160 the plot. For example, BL/0/0 will align the lower left corner
161 of the time stamp with the lower left corner of the plot.
162 Optionally, append a label, or c (which will plot the command
163 string.). The GMT parameters UNIX_TIME, UNIX_TIME_POS, and
164 UNIX_TIME_FORMAT can affect the appearance; see the gmtdefaults
165 man page for details. The time string will be in the locale set
166 by the environment variable TZ (generally local time).
167 -V Selects verbose mode, which will send progress reports to stderr
169 [Default runs "silently"].
170 -W Set pen attributes used for vector outlines [Default: width = 1,
172 color = black, texture = solid]. (See SPECIFYING PENS below).
173 -X -Y Shift plot origin relative to the current origin by (x-shift,y-
175 shift) and optionally append the length unit (c, i, m, p). You
176 can prepend a to shift the origin back to the original position
177 after plotting, or prepend r [Default] to reset the current
178 origin to the new location. If -O is used then the default (x-
179 shift,y-shift) is (0,0), otherwise it is (r1i, r1i) or (r2.5c,
180 r2.5c). Alternatively, give c to align the center coordinate (x
181 or y) of the plot with the center of the page based on current
182 page size.
183 -Z Means the angles provided are azimuths rather than direction
185 (requires -A).
186 -c Specifies the number of plot copies. [Default is 1].
188 -f Special formatting of input and/or output columns (time or geo‐
190 graphical data). Specify i or o to make this apply only to
191 input or output [Default applies to both]. Give one or more
192 columns (or column ranges) separated by commas. Append T (abso‐
193 lute calendar time), t (relative time in chosen TIME_UNIT since
194 TIME_EPOCH), x (longitude), y (latitude), or f (floating point)
195 to each column or column range item. Shorthand -f[i|o]g means
196 -f[i|o]0x,1y (geographic coordinates).
197 SPECIFYING PENS
199 pen The attributes of lines and symbol outlines as defined by pen is
200 a comma delimetered list of width, color and texture, each of
201 which is optional. width can be indicated as a measure (points,
202 centimeters, inches) or as faint, thin[ner|nest], thick[er|est],
203 fat[ter|test], or obese. color specifies a grey shade or color
204 (see SPECIFYING COLOR below). texture is a combination of
205 dashes `-' and dots `.'.
206 SPECIFYING FILL
208 fill The attribute fill specifies the solid shade or solid color (see
209 SPECIFYING COLOR below) or the pattern used for filling poly‐
210 gons. Patterns are specified as pdpi/pattern, where pattern
211 gives the number of the built-in pattern (1-90) or the name of a
212 Sun 1-, 8-, or 24-bit raster file. The dpi sets the resolution
213 of the image. For 1-bit rasters: use Pdpi/pattern for inverse
214 video, or append :Fcolor[B[color]] to specify fore- and back‐
215 ground colors (use color = - for transparency). See GMT Cook‐
216 book & Technical Reference Appendix E for information on indi‐
217 vidual patterns.
218 SPECIFYING COLOR
220 color The color of lines, areas and patterns can be specified by a
221 valid color name; by a grey shade (in the range 0-255); by a
222 decimal color code (r/g/b, each in range 0-255; h-s-v, ranges
223 0-360, 0-1, 0-1; or c/m/y/k, each in range 0-1); or by a hexa‐
224 decimal color code (#rrggbb, as used in HTML). See the gmtcol‐
225 ors manpage for more information and a full list of color names.
226
228 GMT is able to recognize many of the commonly used grid file formats,
229 as well as the precision, scale and offset of the values contained in
230 the grid file. When GMT needs a little help with that, you can add the
231 suffix =id[/scale/offset[/nan]], where id is a two-letter identifier of
232 the grid type and precision, and scale and offset are optional scale
233 factor and offset to be applied to all grid values, and nan is the
234 value used to indicate missing data. See grdreformat(1) and Section
235 4.17 of the GMT Technical Reference and Cookbook for more information.
236 When reading a netCDF file that contains multiple grids, GMT will read,
238 by default, the first 2-dimensional grid that can find in that file. To
239 coax GMT into reading another multi-dimensional variable in the grid
240 file, append ?varname to the file name, where varname is the name of
241 the variable. Note that you may need to escape the special meaning of ?
242 in your shell program by putting a backslash in front of it, or by
243 placing the filename and suffix between quotes or double quotes. See
244 grdreformat(1) and Section 4.18 of the GMT Technical Reference and
245 Cookbook for more information, particularly on how to read splices of
246 3-, 4-, or 5-dimensional grids.
247
249 To draw the vector field given by the files r.grd and theta.grd on a
250 linear plot with scale 5 cm per data unit, using vector rather than
251 stick plot, and scale vector magnitudes so that 10 units equal 1 inch,
252 run
253 grdvector r.grd theta.grd -Jx5c -A -Q -S10i > gradient.ps
255
258 GMT(1), grdcontour(1), psxy(1)
259GMT 4.3.1 15 May 2008 GRDVECTOR(1)