NAME

       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 grdgradient and modified by grdmath or grdhisteq. Each grid-node in the
       grdfile is represented as a shaded (or colored) rectangle centered on  the  grid  node.  When  using  map
       projections,  the grid is first resampled on a new rectangular 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 MEASURE_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 origin)
              -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 Equator 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 manpages.

OPTIONS

       No space between the option flag and the associated arguments.

       -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 the input file.

       -G     This option only applies when the resulting image 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.

       -bo    Selects binary output. Append s for single precision [Default is double].

       -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
              minutes [and seconds], use the dd:mm[:ss] format. Append r if  lower  left  and  upper  right  map
              coordinates  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 specified 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 categorical data where interpolating between values is meaningless.

       -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.). The GMT parameters UNIX_TIME and UNIX_TIME_POS can affect
              the appearance; see the gmtdefaults man page for details.

       -V     Selects verbose mode, which will send progress reports to stderr [Default runs "silently"].

       -X -Y  Shift origin of plot by (x-shift,y-shift).  Prepend a for absolute coordinates;  the  default  (r)
              will 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 tickmarks, 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 colors.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(1gmt), grdcontour(1gmt), grdview(1gmt), grdgradient(1gmt), grdhisteq(1gmt)

                                                   1 Jan 2004                                        GRDIMAGE(l)