grdedit - Modifying the header in a 2-D grdfile


       grdedit  grdfile [ -A ] [ -Dxunit/yunit/zunit/scale/offset/title/remark
       ] [ -Nxyzfile ] [ -Rwest/east/south/north[r] ] [ -S ] [ -V ]
        [ -: ] [ -bi[s][n] ] [ -f[i|o]colinfo ]


       grdedit reads the header  information  in  a  binary  2-D  grdfile  and
       replaces  the  information with values provided on the command line [if
       any]. As an option, global, geographical grids (with 360 degrees longi-
       tude  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 grdheader.
               No  space between the option flag and the associated arguments.
       Use upper case for the option flags and lower case for modifiers.

              Name of the 2-D grdfile to modify


       -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 gridfiles
              (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.

       -D     Give new values for xunit, yunit, zunit, scale,  offset,  title,
              and remark.  To leave some of the values untouched, specify = as
              the new value.

       -H     Input file(s) has Header record(s). Number of header records can
              be  changed  by  editing  your  .gmtdefaults4 file. If used, GMT
              default is 1 header record. Use -Hi if only  input  data  should
              have  header  records  [Default will write out header records if
              the input data have them].

       -N     Read the ascii (or binary; see -bi) file xyzfile and replace the
              corresponding nodal values in the grid with these z values.

       -R     xmin,  xmax,  ymin, and ymax specify the Region of interest. For
              geographic regions,  these  limits  correspond  to  west,  east,
              south,  and north and you may specify them in decimal degrees or
              in [+-]dd:mm[][W|E|S|N] format. Append r  if  lower  left
              and  upper  right map coordinates are given instead of wesn. The
              two shorthands  -Rg  -Rd  stand  for  global  domain  (0/360  or
              -180/+180  in longitude respectively, with -90/+90 in latitude).
              For calendar time coordinates you may either give relative  time
              (relative  to  the  selected  TIME_EPOCH  and  in  the  selected
              TIME_UNIT; append t to -JX|x), or  absolute  time  of  the  form
              [date]T[clock]  (append  T  to  -JX|x). At least one of date and
              clock must be present; the T is always required. The date string
              must  be  of  the form [-]yyyy[-mm[-dd]] (Gregorian calendar) or
              yyyy[-Www[-d]] (ISO week calendar), while the clock string  must
              be  of  the form hh:mm:ss[.xxx]. The use of delimiters and their
              type and positions must be as indicated  (however,  input/output
              and plotting formats are flexible).  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
              laterally according to the new borders given in -R.

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

       -bi    Selects  binary input. Append s for single precision [Default is
              double].  Append n for the  number  of  columns  in  the  binary
              [Default is 3 input columns].

       -f     Special  formatting  of  input  and output columns (time or geo-
              graphical data) Specify i(nput) or  o(utput)  [Default  is  both
              input  and output].  Give one or more columns (or column ranges)
              separated by commas.  Append T (Absolute calendar time), t (time
              relative  to  chosen TIME_EPOCH), x (longitude), y (latitude), g
              (geographic coordinate), or f (floating point) to each column or
              column range item.


       Let  us assume the file data.grd 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

       grdedit data.grd -R-60/-50/10/30 -D=/=/=/=/=/"Gravity Anomalies"/=

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

       grdedit world.grd -R-180/180/-72/72 -S

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

       grdedit junk.grd -A


       gmt(l), grd2xyz(l), xyz2grd(l)

GMT4.0                            1 Oct 2004                        GRDEDIT(l)

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