grdproject

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

SYNOPSIS

       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 ]

DESCRIPTION

       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  associ­
       ated  arguments.  Use  upper case for the option flags and
       lower case for modifiers.

       in_grdfile
              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  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/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.

       -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.

OPTIONS

       -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).


       -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 -A.

       -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 "silently"].

EXAMPLES

       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  parame­
       ters.
       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

RESTRICTIONS

       (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.

SEE ALSO

       gmt(l), gmtdefaults(l), mapproject(l)