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 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 -
              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)
              -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
              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.

       -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"].

       -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 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)



                            1 Mar 2002                GRDIMAGE(l)

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