GRDVECTOR(1) Generic Mapping Tools GRDVECTOR(1)NAMEgrdvector - Plot vector fields from grid files
SYNOPSISgrdvector 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 ]
DESCRIPTIONgrdvector reads two 2-D grid files which represents the x- and y-compo‐
nents 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 dimen‐
sion, or min dimension, append h, +, or - to the width, respec‐
tively.
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 paral‐
lel)
-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 sys‐
tem].
-P Selects Portrait plotting mode [Default is Landscape, see gmtde‐
faults 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 lati‐
tude). 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 delim‐
iters 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 measure‐
ment 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 geo‐
graphical 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 (abso‐
lute 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 poly‐
gons. 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 back‐
ground colors (use color = - for transparency). See GMT Cook‐
book & Technical Reference Appendix E for information on indi‐
vidual 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 hexa‐
decimal color code (#rrggbb, as used in HTML). See the gmtcol‐
ors 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 ALSOGMT(1), gmtcolors(5), grdcontour(1), psxy(1)GMT 4.5.14 1 Nov 2015 GRDVECTOR(1)
