NAME

       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 coordi-
       nate 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 sensi-
       ble values for the search_radius.  The new node spacing may  be  deter-
       mined  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.

       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 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 paral-
              lel)
              -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 Car-
              ree))
              -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.

       -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.


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 spec-
              ified 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 -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  cre-
       ated 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


RESTRICTIONS

       The boundaries of a projected (rectangular) data set will not necessar-
       ily give rectangular geographical boundaries (Mercator  is  one  excep-
       tion). 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)



GMT3.4.6                          1 Jan 2005                     GRDPROJECT(l)

Man(1) output converted with man2html