grdvector
grdvector - Plot vector fields from grdfiles
SYNOPSIS
grdvector compx.grd compy.grd -Jparameters [ -A ] [
-Btickinfo ] [ -Ccptfile ] [ -E ] [ -Gfill] [
-Ix_inc[m|c][/y_inc[m|c]] ] [ -K ] [ -N ] [ -O ] [ -P ] [
-Qparameters ] [ -Rwest/east/south/north[r] ] [ -S[l]scale
] [ -T ] [ -U[/dx/dy/][label] ] [ -V ] [ -Wcontourpen ] [
-Xx-shift ] [ -Yy-shift ] [ -Z ] [ -ccopies ]
DESCRIPTION
grdvector reads two 2-D gridded files which represents the
x- and y-components of a vector field and produces a vec
tor field plot by drawing vectors with orientation and
length according to the information in the files. Alterna
tively, 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.
-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 MEA
SURE_UNIT setting in .gmtdefaults, but this can be
overridden on the command line by appending the c,
i, or m to the scale/width value.
CYLINDRICAL PROJECTIONS:
-Jclon0/lat0/scale (Cassini)
-Jjlon0/scale (Miller)
-Jmscale (Mercator - Greenwich and Equator as ori
gin)
-Jmlon0/lat0/scale (Mercator - Give meridian and
standard parallel)
-Joalon0/lat0/azimuth/scale (Oblique Mercator -
point and azimuth)
-Joblon0/lat0/lon1/lat1/scale (Oblique Mercator -
two points)
-Joclon0/lat0/lonp/latp/scale (Oblique Mercator -
point and pole)
-Jqlon0/scale (Equidistant Cylindrical Projection
(Plate Carree))
-Jtlon0/scale (TM - Transverse Mercator, with Equa
tor as y = 0)
-Jtlon0/lat0/scale (TM - Transverse Mercator, set
origin)
AZIMUTHAL PROJECTIONS:
-Jalon0/lat0/scale (Lambert).
-Jelon0/lat0/scale (Equidistant).
-Jflon0/lat0/horizon/scale (Gnomonic).
-Jglon0/lat0/scale (Orthographic).
-Jslon0/lat0/[slat/]scale (General Stereographic)
CONIC PROJECTIONS:
-Jblon0/lat0/lat1/lat2/scale (Albers)
-Jdlon0/lat0/lat1/lat2/scale (Equidistant)
-Jllon0/lat0/lat1/lat2/scale (Lambert)
MISCELLANEOUS PROJECTIONS:
-Jhlon0/scale (Hammer)
-Jilon0/scale (Sinusoidal)
-Jk[f|s]lon0/scale (Eckert IV (f) and VI (s))
-Jnlon0/scale (Robinson)
-Jrlon0/scale (Winkel Tripel)
-Jvlon0/scale (Van der Grinten)
-Jwlon0/scale (Mollweide)
NON-GEOGRAPHICAL PROJECTIONS:
-Jp[a]scale[/origin] (polar (theta,r) coordinates,
optional a for azimuths and offset theta [0])
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log,
and power scaling)
More details can be found in the psbasemap man
pages.
OPTIONS
No space between the option flag and the associated argu
ments.
-A Means grdfiles have polar (r, theta) components
instead of Cartesian (x, y).
-B Sets map boundary tickmark intervals. See psbasemap
for 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]. Specify the shade (0-255) or color
of a Sun 1-, 8-, or 24-bit raster file. dpi sets
the resolution of the image. For 1-bit rasters: use
-GP for inverse video, or append :Fr/g/b[B[r/g/b]]
to specify fore- and background colors (use r/g/b =
- for transparency). See GMT Cookbook & Technical
Reference Appendix E for information on individual
patterns.
-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 [GMT Default is
Landscape, see gmtdefaults to change this].
-Q Select vector plot [Default is stick-plot]. Option
ally, 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 appearence scaled by length/size.
-R west, east, south, and north specify the Region of
interest. To specify boundaries in degrees and min
utes [and seconds], use the dd:mm[:ss] format.
Append r if lower left and upper right map coordi
nates are given instead of wesn. Specify a subset
of the grid.
-S Sets scale for vector length in data units per dis
tance 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 vec
tors.
-T Means azimuth should be converted to angles based
on the selected map projection.
-U Draw Unix System time stamp on plot. User may spec
ify where the lower left corner of the stamp should
fall on the page relative to lower left corner of
plot. Optionally, append a label, or c (which will
ance; see the gmtdefaults man page for details.
-V Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
-W Set pen attributes used for vector outlines
[Default: width = 1, color = 0/0/0, texture =
solid].
-X -Y Shift origin of plot by (x-shift,y-shift). Prepend
a for absolute coordinates; the default (r) will
reset plot origin.
-Z Means the angles provided are azimuths rather than
direction (requires -A).
-c Specifies the number of plot copies. [Default is 1]
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 mag
nitudes so that 10 units equal 1 inch, try
grdvector r.grd theta.grd -Jx5c -Q -S10i > gradient.ps
SEE ALSO
gmt(l), grdcontour(l), psxy(l)
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