grdimage
grdimage - Create grayshaded or colored image from a 2-D
netCDF grd file
SYNOPSIS
grdimage grdfile -Ccptfile -Jparameters [ -Btickinfo ] [
-Edpi ] [ -G[f|b]rgb ] [ -Iintensfile] [ -K ] [ -M ] [ -O
] [ -P ] [ -Rwest/east/south/north[r] ] [ -Ssearch_radius
] [ -T[s] ] [ -U[/dx/dy/][label] ] [ -V ] [ -Xx-shift ] [
-Yy-shift ] [ -ccopies ]
DESCRIPTION
grdimage reads a 2-D gridded file and produces a gray-
shaded (or colored) map by assigning each contour interval
a gray-shade (or color). Optionally, illumination may be
added by providing a file with intensities in the (-1,+1)
range. Values outside this range will be clipped. Such
intensity files can be created from the grdfile using grd
gradient and modified by grdmath or grdhisteq. Each grid-
node in the grdfile is represented as a shaded (or col
ored) rectangle centered on the grid node. When using map
projections, the grid is first resampled on a new rectan
gular grid (This can be a time-consuming process for large
grid files; but see -T). A 24-bit true color PostScript
file is output. The region option can be used to select a
map region larger or smaller than that implied by the
extent of the grdfile.
grdfile
2-D gridded data set to be imaged
-C name of the color palette table
-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 -
(Plate Carree))
-Jtlon0/scale (TM - Transverse Mercator, with Equa
tor as y = 0)
-Jtlon0/lat0/scale (TM - Transverse Mercator, set
origin)
-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/[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.
-B Sets map boundary tickmark intervals. See psbasemap
for details.
-E Sets the resolution of the projected grid that will
be created if a map projection other than Linear or
Mercator was selected. By default, the projected
grid will be of the same size (rows and columns) as
otherwise would consist of only two colors: black
(0) and white (255). If so, this option will
instead use the image as a transparent mask and
point the mask (or its inverse, with -Gb) with the
given color combination.
-I Gives the name of a grdfile with intensities in the
(-1,+1) range. [Default is no illumination].
-K More PostScript code will be appended later
[Default terminates the plot system].
-M Force conversion to monochrome image using the
(television) YIQ transformation.
-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].
-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. You may ask for a
larger w/e/s/n region to have more room between the
image and the axes. A smaller region than speci
fied in the grdfile will result in a subset of the
grid [Default is region given by the grdfile].
-S Set the search radius for the averaging procedure
[Default avoids aliasing].
-T Plot image without any interpolation. This involves
converting each node-centered bin into a polygon
which is then painted separately. Append s to skip
nodes with z = NaN. This option is useful for cate
gorical data where interpolating between values is
meaningless.
-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
plot the command string.). The GMT parameters
UNIX_TIME and UNIX_TIME_POS can affect the appear
ance; see the gmtdefaults man page for details.
-V Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
reset plot origin.
-c Specifies the number of plot copies. [Default is 1]
EXAMPLES
To gray-shade the file hawaii_grav.grd with shades given
in shades.cpt on a Lambert map at 1.5 cm/degree along the
standard parallels 18 and 24, and using 1 degree tick
marks, try
grdimage hawaii_grav.grd -Jl18/24/1.5c -Cshades.cpt -B1 >
hawaii_grav_image.ps
To create an illuminated color PostScript plot of the
gridded data set image.grd, using the intensities provided
by the file intens.grd, and color levels in the file col
ors.cpt, with linear scaling at 10 inch/x-unit, tickmarks
every 5 units, try
grdimage image.grd -Jx10i -Ccolors.cpt -Iintens.grd -B5 >
image.ps
SEE ALSO
gmt(l), grdcontour(l), grdview(l), grdgradient(l), grdhis
teq(l)
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