NAME
grdedit - Modifying the header in a 2-D grdfile
SYNOPSIS
grdedit grdfile [ -A ] [
-Dxunit/yunit/zunit/scale/offset/title/remark ] [
-Rwest/east/south/north[r] ] [ -S ]
DESCRIPTION
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 longitude range) can be rotated in
the east-west direction. 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.
grdfile
Name of the 2-D grdfile to modify
OPTIONS
-A If necessary, adjust the file's x_inc, y_inc to be com-
patible 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.
-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. 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.
EXAMPLES
Let us assume the file data.grd covers the area
300/310/10/30. We want to change the boundaries from geo-
detic 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 incompa-
tible -R and -I arguments. To reset the x- and y-increments
we run
grdedit junk.grd -A
SEE ALSO
gmt(l), grd2xyz(l), xyz2grd(l)