NAME
grdvector - Plot vector fields from grdfiles
SYNOPSIS
grdvector compx.grd compy.grd -Jparameters [ -A ] [ -Btick-
info ] [ -Ccptfile ] [ -E ] [ -Gfill] [
-Ix_inc[m|c][/y_inc[m|c]] ] [ -K ] [ -N ] [ -O ] [ -P ] [
-Qparameters ] [ -Rwest/east/south/north[r] ] [ -Sscale ] [
-T ] [ -U[/dx/dy/][label] ] [ -V ] [ -Wcontourpen ] [ -Xx-
shift ] [ -Yy-shift ] [ -Zzlevel ] [ -ccopies ]
DESCRIPTION
grdvector reads two 2-D gridded files which represents the
x- and y-components 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). grdvec-
tor 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 MEASURE_UNIT set-
ting 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 origin)
-Jmlon0/lat0/scale (Mercator - Give meridian and stan-
dard 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 Equator
as y = 0)
-Jtlon0/lat0/scale (TM - Transverse Mercator, set ori-
gin)
-Juzone/scale (UTM - Universal Transverse Mercator)
-Jylon0/lats/scale (Basic Cylindrical Projection)
AZIMUTHAL PROJECTIONS:
-Jalon0/lat0/scale (Lambert).
-Jelon0/lat0/scale (Equidistant).
-Jflon0/lat0/horizon/scale (Gnomonic).
-Jglon0/lat0/scale (Orthographic).
-Jslon0/lat0/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:
-Jpscale[/origin] (polar (theta,r) coordinates, option-
ally offset theta [0])
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log, and
power scaling)
More details can be found in the psbasemap manpages.
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 (r/g/b), or
-Gpdpi/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. 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 back-
ground 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 minutes
[and seconds], use the dd:mm[:ss] format. Append r if
lower left and upper right map coordinates are given
instead of wesn. Specify a subset of the grid.
-S Sets scale for vector length in data units per distance
measurement unit [1].
-T Means azimuth should be converted to angles based on
the selected map projection.
-U Draw Unix System time stamp on plot. User may specify
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 plot the
command string.)
-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 magni-
tudes so that 10 units equal 1 inch, try
grdvector r.grd theta.grd -Jx5c -Q -S0.1i > gradient.ps
SEE ALSO
gmt(l), grdcontour(l), psxy(l)