NAME

       grdedit - Modify header or content of a grid

SYNOPSIS

       grdedit         grid         [          -A         ]        [         -C        ]        [
       -D[+xxname][+yyname][+zzname][+sscale][+ooffset][+ninvalid][+ttitle][+rremark]     ]     [
       -E[a|h|l|r|t|v]  ]  [   -Goutgrid ] [  -Jparameters ] [  -Ntable ] [  -Rregion ] [  -S ] [
       -T ] [  -V[level] ] [ -bibinary ] [ -dinodata ] [ -eregexp ] [ -fflags ] [ -:[i|o] ]

       Note: No space is allowed between the option flag and the associated arguments.

DESCRIPTION

       grdedit reads the  header  information  in  a  binary  2-D  grid  file  and  replaces  the
       information  with  values  provided  on  the  command line [if any]. As an option, global,
       geographical grids (with 360 degrees longitude range) can  be  rotated  in  the  east-west
       direction,  and  individual  nodal  values can be replaced from a table of x, y, z values.
       grdedit only operates on files containing a grid header.  Note:  If  it  is  important  to
       retain the original data you should use -G to save the modified grid to a new file.

REQUIRED ARGUMENTS

       grid   Name of the 2-D grid file to modify. (See GRID FILE FORMATS below).

OPTIONAL ARGUMENTS

       -A     If necessary, adjust the file’s x_inc, y_inc to be compatible with its domain (or a
              new domain set with -R). Older grid files (i.e., created prior to  GMT  3.1)  often
              had  excessive slop in x_inc, y_inc and an adjustment is necessary. Newer files are
              created correctly.

       -C     Clear the command history from the grid header.

       -D[+xxname][+yyname][+zzname][+sscale][+ooffset][+ninvalid][+ttitle][+rremark]
              Give one or more combinations for values xname, yname, zname  (give  the  names  of
              those  variables  and  in square bracket their units, e.g., “distance [km]”), scale
              (to multiply grid values after read [normally 1]), offset (to  add  to  grid  after
              scaling  [normally  0]),  invalid  (a value to represent missing data [NaN]), title
              (anything you like), and remark (anything you like). Items not listed  will  remain
              untouched.   Give a blank name to completely reset a particular string.  Use quotes
              to group texts with more than one word.  Note that for geographic grids (-fg) xname
              and yname are set automatically.

       -E[a|h|l|r|t|v]
              Transform  the  grid  in  one  of  six ways and (for l|r|t) interchange the x and y
              information: -Ea will rotate the grid around 180 degrees, -Eh will  flip  the  grid
              horizontally (left-to-right), -El will rotate the grid 90 degrees counter-clockwise
              (left), -Er will rotate the grid 90 degrees clockwise (right), -Et  will  transpose
              the   grid   [Default],   -Ev   will  flip  the  grid  vertically  (top-to-bottom).
              Incompatible with the other options (except -G).

       -Goutgrid
              Normally, grdedit will overwrite the existing grid with the modified grid.  Use  -G
              to write the modified grid to the file outgrid instead.

       -Jparameters (more …)
              Select  map  projection.  Use the -J syntax to save the georeferencing info as CF-1
              compliant metadata in netCDF grids. This metadata will be recognized by GDAL.

       -Ntable
              Read the ASCII (or binary; see -bi) file table and replace the corresponding  nodal
              values in the grid with these x,y,z values.

       -Rxmin/xmax/ymin/ymax[+r][+uunit] (more …)
              Specify  the  region  of interest. The new w/e/s/n values will replace those in the
              grid, and the x_inc, y_inc values are adjusted, if necessary.

       -S     For global, geographical grids only. Grid values  will  be  shifted  longitudinally
              according to the new borders given in -R.

       -T     Make  necessary  changes  in  the header to convert a gridline-registered grid to a
              pixel-registered grid, or vice-versa.  Basically,  gridline-registered  grids  will
              have their domain extended by half the x- and y-increments whereas pixel-registered
              grids will have their domain shrunk by the same amount.

       -V[level] (more …)
              Select verbosity level [c].

       -bi[ncols][t] (more …)
              Select native binary input. [Default is 3 input columns].

       -dinodata (more …)
              Replace input columns that equal nodata with NaN.

       -e[~]”pattern” | -e[~]/regexp/[i] (more …)
              Only accept data records that match the given pattern.

       -f[i|o]colinfo (more …)
              Specify data types of input and/or output columns.

       -h[i|o][n][+c][+d][+rremark][+rtitle] (more …)
              Skip or produce header record(s).

       -^ or just -
              Print a short message about the syntax of the command, then exits (NOTE: on Windows
              just use -).

       -+ or just +
              Print  an  extensive  usage  (help)  message,  including  the  explanation  of  any
              module-specific option (but not the GMT common options), then exits.

       -? or no arguments
              Print a complete usage (help) message, including the explanation  of  all  options,
              then exits.

GRID FILE FORMATS

       By  default  GMT  writes  out grid as single precision floats in a COARDS-complaint netCDF
       file format. However, GMT is able to produce grid files in many other commonly  used  grid
       file formats and also facilitates so called “packing” of grids, writing out floating point
       data as 1- or 2-byte integers. (more …)

GEOGRAPHICAL AND TIME COORDINATES

       When the output grid  type  is  netCDF,  the  coordinates  will  be  labeled  “longitude”,
       “latitude”, or “time” based on the attributes of the input data or grid (if any) or on the
       -f or -R options. For example, both  -f0x  -f1t  and  -R90w/90e/0t/3t  will  result  in  a
       longitude/time grid. When the x, y, or z coordinate is time, it will be stored in the grid
       as relative time since epoch as specified by TIME_UNIT and TIME_EPOCH in the gmt.conf file
       or on the command line. In addition, the unit attribute of the time variable will indicate
       both this unit and epoch.

EXAMPLES

       Let us assume the file data.nc covers the  area  300/310/10/30.  We  want  to  change  the
       boundaries  from  geodetic  longitudes to geographic and put a new title in the header. We
       accomplish this by

              gmt grdedit data.nc -R-60/-50/10/30 -D+t"Gravity Anomalies"

       The grid world.nc has the limits 0/360/-72/72. To shift the data so that the limits  would
       be -180/180/-72/72, use

              gmt grdedit world.nc -R-180/180/-72/72 -S

       The  file  junk.nc  was created prior to GMT 3.1 with incompatible -R and -I arguments. To
       reset the x- and y-increments we run

              gmt grdedit junk.nc -A

       The file junk.nc was created prior  to  GMT  4.1.3  and  does  not  contain  the  required
       information to indicate that the grid is geographic. To add this information, run

              gmt grdedit junk.nc -fg

       To  rotate the grid oblique.nc 90 degrees counter-clockwise and write out the rotated grid
       to a new file, run

              gmt grdedit oblique.nc -El -Goblique_rot.nc

SEE ALSO

       gmt, grd2xyz, grdinfo xyz2grd

COPYRIGHT

       2018, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe