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 grid files which represents the x- and y-compo‐
18 nents of a vector field and produces a vector field plot by drawing
19 vectors with orientation and length according to the information in the
20 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 -Jpoly/[lon0/[lat0/]]scale ((American) Polyconic)
66 AZIMUTHAL PROJECTIONS:
68 -Jalon0/lat0[/horizon]/scale (Lambert Azimuthal Equal-Area)
70 -Jelon0/lat0[/horizon]/scale (Azimuthal Equidistant)
71 -Jflon0/lat0[/horizon]/scale (Gnomonic)
72 -Jglon0/lat0[/horizon]/scale (Orthographic)
73 -Jglon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale
74 (General Perspective).
75 -Jslon0/lat0[/horizon]/scale (General Stereographic)
76 MISCELLANEOUS PROJECTIONS:
78 -Jh[lon0/]scale (Hammer)
80 -Ji[lon0/]scale (Sinusoidal)
81 -Jkf[lon0/]scale (Eckert IV)
82 -Jk[s][lon0/]scale (Eckert VI)
83 -Jn[lon0/]scale (Robinson)
84 -Jr[lon0/]scale (Winkel Tripel)
85 -Jv[lon0/]scale (Van der Grinten)
86 -Jw[lon0/]scale (Mollweide)
87 NON-GEOGRAPHICAL PROJECTIONS:
89 -Jp[a]scale[/origin][r|z] (Polar coordinates (theta,r))
91 -Jxx-scale[d|l|ppow|t|T][/y-scale[d|l|ppow|t|T]] (Linear, log,
92 and power scaling)
93
95 No space between the option flag and the associated arguments.
96 -A Means grid files have polar (r, theta) components instead of
98 Cartesian (x, y).
99 -B Sets map boundary annotation and tickmark intervals; see the
101 psbasemap man page for all the details.
102 -C Use cptfile to assign colors based on vector length.
104 -E Center vectors on grid nodes [Default draws from grid node].
106 -G Sets color or shade for vector interiors [Default is no fill].
108 (See SPECIFYING FILL below).
109 -I Only plot vectors at nodes every x_inc, y_inc apart (must be
111 multiples of original grid spacing). Append m for minutes or c
112 for seconds. [Default plots every node].
113 -K More PostScript code will be appended later [Default terminates
115 the plot system].
116 -N Do NOT clip vectors at map boundaries [Default will clip].
118 -O Selects Overlay plot mode [Default initializes a new plot sys‐
120 tem].
121 -P Selects Portrait plotting mode [Default is Landscape, see gmtde‐
123 faults to change this].
124 -Q Select vector plot [Default is stick-plot]. Optionally, specify
126 parameters which are arrowwidth/headlength/headwidth [Default is
127 0.075c/0.3c/0.25c (or 0.03i/0.12i/0.1i)]. Append nsize which
128 will cause vectors shorter than size to have their appearance
129 scaled by length/size.
130 -R xmin, xmax, ymin, and ymax specify the Region of interest. For
132 geographic regions, these limits correspond to west, east,
133 south, and north and you may specify them in decimal degrees or
134 in [+-]dd:mm[:ss.xxx][W|E|S|N] format. Append r if lower left
135 and upper right map coordinates are given instead of w/e/s/n.
136 The two shorthands -Rg and -Rd stand for global domain (0/360
137 and -180/+180 in longitude respectively, with -90/+90 in lati‐
138 tude). Alternatively, specify the name of an existing grid file
139 and the -R settings (and grid spacing, if applicable) are copied
140 from the grid. For calendar time coordinates you may either
141 give (a) relative time (relative to the selected TIME_EPOCH and
142 in the selected TIME_UNIT; append t to -JX|x), or (b) absolute
143 time of the form [date]T[clock] (append T to -JX|x). At least
144 one of date and clock must be present; the T is always required.
145 The date string must be of the form [-]yyyy[-mm[-dd]] (Gregorian
146 calendar) or yyyy[-Www[-d]] (ISO week calendar), while the clock
147 string must be of the form hh:mm:ss[.xxx]. The use of delim‐
148 iters and their type and positions must be exactly as indicated
149 (however, input, output and plot formats are customizable; see
150 gmtdefaults). Specify a subset of the grid.
151 -S Sets scale for vector length in data units per distance measure‐
153 ment unit [1]. Append c, i, m, p to indicate the measurement
154 unit (cm, inch, m, point). Prepend l to indicate a fixed length
155 for all vectors.
156 -T Means azimuth should be converted to angles based on the
158 selected map projection.
159 -U Draw Unix System time stamp on plot. By adding just/dx/dy/, the
161 user may specify the justification of the stamp and where the
162 stamp should fall on the page relative to lower left corner of
163 the plot. For example, BL/0/0 will align the lower left corner
164 of the time stamp with the lower left corner of the plot.
165 Optionally, append a label, or c (which will plot the command
166 string.). The GMT parameters UNIX_TIME, UNIX_TIME_POS, and
167 UNIX_TIME_FORMAT can affect the appearance; see the gmtdefaults
168 man page for details. The time string will be in the locale set
169 by the environment variable TZ (generally local time).
170 -V Selects verbose mode, which will send progress reports to stderr
172 [Default runs "silently"].
173 -W Set pen attributes used for vector outlines [Default: width =
175 0.25p, color = black, texture = solid]. (See SPECIFYING PENS
176 below).
177 -X -Y Shift plot origin relative to the current origin by (x-shift,y-
179 shift) and optionally append the length unit (c, i, m, p). You
180 can prepend a to shift the origin back to the original position
181 after plotting, or prepend r [Default] to reset the current
182 origin to the new location. If -O is used then the default (x-
183 shift,y-shift) is (0,0), otherwise it is (r1i, r1i) or (r2.5c,
184 r2.5c). Alternatively, give c to align the center coordinate (x
185 or y) of the plot with the center of the page based on current
186 page size.
187 -Z Means the angles provided are azimuths rather than direction
189 (requires -A).
190 -c Specifies the number of plot copies. [Default is 1].
192 -f Special formatting of input and/or output columns (time or geo‐
194 graphical data). Specify i or o to make this apply only to
195 input or output [Default applies to both]. Give one or more
196 columns (or column ranges) separated by commas. Append T (abso‐
197 lute calendar time), t (relative time in chosen TIME_UNIT since
198 TIME_EPOCH), x (longitude), y (latitude), or f (floating point)
199 to each column or column range item. Shorthand -f[i|o]g means
200 -f[i|o]0x,1y (geographic coordinates).
201 SPECIFYING PENS
203 pen The attributes of lines and symbol outlines as defined by pen is
204 a comma delimetered list of width, color and texture, each of
205 which is optional. width can be indicated as a measure (points,
206 centimeters, inches) or as faint, thin[ner|nest], thick[er|est],
207 fat[ter|test], or obese. color specifies a gray shade or color
208 (see SPECIFYING COLOR below). texture is a combination of
209 dashes `-' and dots `.'.
210 SPECIFYING FILL
212 fill The attribute fill specifies the solid shade or solid color (see
213 SPECIFYING COLOR below) or the pattern used for filling poly‐
214 gons. Patterns are specified as pdpi/pattern, where pattern
215 gives the number of the built-in pattern (1-90) or the name of a
216 Sun 1-, 8-, or 24-bit raster file. The dpi sets the resolution
217 of the image. For 1-bit rasters: use Pdpi/pattern for inverse
218 video, or append :Fcolor[B[color]] to specify fore- and back‐
219 ground colors (use color = - for transparency). See GMT Cook‐
220 book & Technical Reference Appendix E for information on indi‐
221 vidual patterns.
222 SPECIFYING COLOR
224 color The color of lines, areas and patterns can be specified by a
225 valid color name; by a gray shade (in the range 0-255); by a
226 decimal color code (r/g/b, each in range 0-255; h-s-v, ranges
227 0-360, 0-1, 0-1; or c/m/y/k, each in range 0-1); or by a hexa‐
228 decimal color code (#rrggbb, as used in HTML). See the gmtcol‐
229 ors manpage for more information and a full list of color names.
230
232 GMT is able to recognize many of the commonly used grid file formats,
233 as well as the precision, scale and offset of the values contained in
234 the grid file. When GMT needs a little help with that, you can add the
235 suffix =id[/scale/offset[/nan]], where id is a two-letter identifier of
236 the grid type and precision, and scale and offset are optional scale
237 factor and offset to be applied to all grid values, and nan is the
238 value used to indicate missing data. See grdreformat(1) and Section
239 4.17 of the GMT Technical Reference and Cookbook for more information.
240 When reading a netCDF file that contains multiple grids, GMT will read,
242 by default, the first 2-dimensional grid that can find in that file. To
243 coax GMT into reading another multi-dimensional variable in the grid
244 file, append ?varname to the file name, where varname is the name of
245 the variable. Note that you may need to escape the special meaning of ?
246 in your shell program by putting a backslash in front of it, or by
247 placing the filename and suffix between quotes or double quotes. See
248 grdreformat(1) and Section 4.18 of the GMT Technical Reference and
249 Cookbook for more information, particularly on how to read splices of
250 3-, 4-, or 5-dimensional grids.
251
253 To draw the vector field given by the files r.grd and theta.grd on a
254 linear plot with scale 5 cm per data unit, using vector rather than
255 stick plot, and scale vector magnitudes so that 10 units equal 1 inch,
256 run
257 grdvector r.grd theta.grd -Jx5c -A -Q -S10i > gradient.ps
259
262 GMT(1), gmtcolors(5), grdcontour(1), psxy(1)
263GMT 4.5.6 10 Mar 2011 GRDVECTOR(1)