NAME

     grdsample - Resample a grd file onto a new grid

SYNOPSIS

     grdsample  in_grdfile  - Gout_grdfile   [   -  F   ]   [   -
     Idx[m|c][/dy[m|c]]  ]  [  - L  ]  [  - Nnx/ny  ]  [ -Q ] [ -
     Rwest/east/south/north[r] ] [ -T ] [ -V ]

DESCRIPTION

     grdsample reads a 2-D binary grd file and resamples it on  a
     new  grid specified by either a new number of nodes or a new
     grid-spacing.  A sub-region may also be selected.  A bicubic
     [Default]  or  bilinear  interpolation is used to sample the
     grid.  Free boundary conditions are assumed  (curvature  and
     3rd normal derivative is zero).  grdsample is mostly used to
     resample a grid onto a finer grid.  Going the other way will
     introduce  aliasing  and  is  better  done  using  grdfft or
     grdfilter.

     in_grdfile
          The name of the input 2-D binary grd file.

     -G    The name of the output grd file.

OPTIONS

     No space between the option flag and  the  associated  argu-
     ments.

     -F    Force pixel registration.  [Default is grid  registra-
          tion].

     -I    x_inc [and optionally  y_inc]  is  the  grid  spacing.
          Append m to indicate minutes or c to indicate seconds.

     -L    Indicates that the input  grdfile  is  a  geographical
          grid.

     -Q    Quick mode, use bilinear rather than bicubic  interpo-
          lation.

     -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.

     -T    Translates between  pixel  registration  and  gridline
          registration.   If  input  data is gridline registered,
          then output will be a pixel grid, and vice versa.   The
          input file's -R and -I are used so no other options are
          necessary (except possibly -Q).

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

EXAMPLES

     To resample the 5 x 5 minute  grid  in  hawaii_5by5_topo.grd
     onto a 1 minute grid, try

     grdsample hawaii_5by5_topo.grd -I1m -Ghawaii_1by1_topo.grd

     To translate the  gridline-registered  file  surface.grd  to
     pixel registration, try

     grdsample surface.grd -T -Gpixel.grd

SEE ALSO

     gmt, grdfft, grdfilter

REFERENCES

     Wessel, P., and W. H. F. Smith, 1995,  The  Generic  Mapping
     Tools  (GMT)  version  3.0  Technical  Reference & Cookbook,
     SOEST/NOAA.
     Wessel, P., and W. H. F. Smith, 1995,  New  Version  of  the
     Generic Mapping Tools Released, EOS Trans. AGU, 76, p. 329.
     Wessel, P., and W. H. F. Smith, 1995,  New  Version  of  the
     Generic           Mapping           Tools          Released,
     http://www.agu.org/eos_elec/95154e.html, Copyright  1995  by
     the American Geophysical Union.
     Wessel, P., and W. H. F. Smith, 1991,  Free  Software  Helps
     Map and Display Data, EOS Trans. AGU, 72, p. 441.