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       grdproject - Forward and Inverse map transformation of 2-D grd files


       grdproject in_grdfile -Jparameters -Rwest/east/south/north[r] [ -A[k|m|n|i|c|p] ] [ -C ] [
       -Ddx[m|c][/dy[m|c]] ] [ -Edpi ] [ -F ] [ -Gout_grdfile ] [ -I ] [ -Mc|i|m|p ] [ -Nnx/ny  ]
       [ -Ssearch_radius ] [ -V ]


       grdproject  will  do  one of two things depending whether -I has been set. If set, it will
       transform a gridded data set from a rectangular  coordinate  system  onto  a  geographical
       system  by  resampling  the  surface  at  the  new  nodes.  If  not set, it will project a
       geographical gridded data set onto a rectangular grid. The new nodes are filled based on a
       simple weighted average of nearby points. Aliasing is avoided by using sensible values for
       the search_radius.  The new node spacing may be determined  in  one  of  several  ways  by
       specifying  the  grid  spacing,  number  of nodes, or resolution. Nodes not constrained by
       input data are set to NaN.
               No space between the option flag and the associated arguments. Use upper case  for
       the option flags and lower case for modifiers.

              2-D binary grd file to be transformed.

       -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.


              -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)


              -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)


              -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)


              -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.

       -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.


       -A     Force  1:1  scaling,  i.e.,  output (or input, see -I) data are in actual projected
              meters. To specify other units, append  k  (km),  m  (mile),n  (nautical  mile),  i
              (inch),  c  (cm),  or p (points).  Without -A, the output (or input, see -I) are in
              the units specified by MEASURE_UNIT (but see -M).

       -C     Let projected coordinates be relative to projection center [Default is relative  to
              lower left corner].

       -D     Set the grid spacing for the new grid. Append m for minutes, c for seconds.

       -E     Set the resolution for the new grid in dots pr inch.

       -F     Toggle between pixel and gridline registration [Default is same as input].

       -G     Specify the name of the output netCDF grd file.

       -I     Do the Inverse transformation, from rectangular to geographical.

       -M     Append  c,  i,  or  m  to  indicate that cm, inch, or meter should be the projected
              measure unit [Default is set by MEASURE_UNIT in .gmtdefaults]. Cannot be used  with

       -N     Set the number of grid nodes in the new grid.

       -S     Set the search radius for the averaging procedure [Default avoids aliasing].

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


       To transform the geographical grid dbdb5.grd onto a pixel Mercator grid at 300 dpi, run

       grdproject dbdb5.grd -R20/50/12/25 -Jm0.25i -E300 -F -Gdbdb5_merc.grd

       To inversely transform the file topo_tm.grd back onto a geographical grid try

       grdproject topo_tm.grd -R-80/-70/20/40 -Jt-75/1:500000 -I -D5m -V -Gtopo.grd

       This assumes, of course, that the coordinates in topo_tm.grd were created  with  the  same
       projection parameters.
       To  inversely  transform  the  file  topo_utm.grd  (which  is  in  UTM meters) back onto a
       geographical grid we specify a one-to-one mapping with meter as the measure unit:

       grdproject topo_utm.grd -R203/205/60/65 -Ju5/1:1 -I -Mm -V -Gtopo.grd


       The boundaries of a projected (rectangular) data set will not necessarily give rectangular
       geographical  boundaries  (Mercator  is  one  exception). In those cases some nodes may be
       unconstrained (set to NaN).  To get a full grid back, your input grid may have to cover  a
       larger area than you are interrested in.


       gmt(1gmt), gmtdefaults(1gmt), mapproject(1gmt)

                                            1 Jan 2004                              GRDPROJECT(l)