.TH GRDEDIT l "1 Jan 2004"
.SH NAME
grdedit \- Modifying the header in a 2-D grdfile
.SH SYNOPSIS
\fBgrdedit\fP \fIgrdfile\fP [ \fB\-A\fP ] [ \fB\-D\fP\fIxunit/yunit/zunit/scale/offset/title/remark\fP ]
[ \fB\-R\fP\fIwest/east/south/north\fP[\fBr\fP] ] [ \fB\-S\fP ] [ \fB\-V\fP ]
.SH DESCRIPTION
\fBgrdedit\fP 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 longitude range) can be rotated in
the east-west direction. \fBgrdedit\fP only operates on files containing a grdheader.
.br
        No space between the option flag and the associated arguments. Use upper case for the
option flags and lower case for modifiers.
.TP
\fIgrdfile\fP
Name of the 2-D grdfile to modify
.sp
.SH OPTIONS
.TP
.B \-A
If necessary, adjust the file's \fIx_inc, y_inc\fP to be compatible with its domain (or a new domain set with \fB\-R\fP).  Older gridfiles (i.e., created prior to GMT 3.1) often had excessive slop in'
\fIx_inc, y_inc\fP and an adjustment is necessary. Newer files are created correctly.
.TP
.B \-D
Give new values for \fIxunit, yunit, zunit, scale, offset, title,\fP and \fIremark\fP.
To leave some of the values untouched, specify = as the new value.
.TP
.B \-R
\fIwest, east, south,\fP and \fInorth\fP specify the Region of interest. To specify boundaries
in degrees and minutes [and seconds], use the dd:mm[:ss] format. Append \fBr\fP if lower left and upper right
map coordinates are given instead of wesn.
The new w/e/s/n values will replace those in the grid, and the \fIx_inc, y_inc\fP
values are adjusted, if necessary.
.TP
.B \-S
For global, geographical grids only. Grid values will be shifted laterally according to
the new borders given in \fB\-R\fP.
.TP
.B \-V
Selects verbose mode, which will send progress reports to stderr [Default runs "silently"].
.SH EXAMPLES
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
.br
.sp
grdedit data.grd \fB\-R\fP-60/-50/10/30 \fB\-D\fP=/=/=/=/=/"Gravity Anomalies"/=
.br
.sp
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
.br
.sp
grdedit world.grd \fB\-R\fP-180/180/-72/72 \fB\-S\fP
.br
.sp
The file junk.grd was created prior to GMT 3.1 with incompatible
\fB\-R\fP and \fB\-I\fP arguments. To reset the x- and y-increments
we run
.br
.sp
grdedit junk.grd \fB\-A\fP
.SH "SEE ALSO"
.IR gmt (1gmt),
.IR grd2xyz (1gmt),
.IR xyz2grd (1gmt)