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
-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[:ss.xxx][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)
Man(1) output converted with