.. index:: ! grdedit

*******
grdedit
*******

.. only:: not man

    grdedit - Modify header or content of a grid

Synopsis
--------

.. include:: common_SYN_OPTs.rst_

**grdedit** *grid* [ |-A| ] [ |-C| ]
[ |-D|\ [**+x**\ *xname*][**+y**\ *yname*][**+z**\ *zname*][**+s**\ *scale*][**+o**\ *offset*][**+n**\ *invalid*][**+t**\ *title*][**+r**\ *remark*] ]
[ |-E|\ [**a**\ \|\ **h**\ \|\ **l**\ \|\ **r**\ \|\ **t**\ \|\ **v**] ]
[ |-G|\ *outgrid* ]
[ |-J|\ *parameters* ]
[ |-N|\ *table* ]
[ |SYN_OPT-R| ]
[ |-S| ] [ |-T| ]
[ |SYN_OPT-V| ]
[ |SYN_OPT-bi| ]
[ |SYN_OPT-di| ]
[ |SYN_OPT-e| ]
[ |SYN_OPT-f| ]
[ |SYN_OPT-:| ]

|No-spaces|

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:

**-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:

**-C**
    Clear the command history from the grid header.

.. _-D:

.. include:: explain_-D_cap.rst_

.. _-E:

**-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**).

.. _-G:

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

.. _-J:

.. |Add_-J| replace:: Use the **-J** syntax to save the georeferencing info as CF-1 compliant
    metadata in netCDF grids. This metadata will be recognized by GDAL.
.. include:: explain_-J.rst_

.. _-N:

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

.. _-R:

.. |Add_-R| replace:: The new w/e/s/n values will
    replace those in the grid, and the *x_inc*, *y_inc* values are
    adjusted, if necessary.
.. include:: explain_-R.rst_

.. _-S:

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

.. _-T:

**-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:

.. |Add_-V| unicode:: 0x20 .. just an invisible code
.. include:: explain_-V.rst_

.. |Add_-bi| replace:: [Default is 3 input columns]. 
.. include:: explain_-bi.rst_

.. |Add_-di| unicode:: 0x20 .. just an invisible code
.. include:: explain_-di.rst_

.. |Add_-e| unicode:: 0x20 .. just an invisible code
.. include:: explain_-e.rst_

.. |Add_-f| unicode:: 0x20 .. just an invisible code
.. include:: explain_-f.rst_

.. |Add_-h| unicode:: 0x20 .. just an invisible code
.. include:: explain_-h.rst_

.. include:: explain_help.rst_

.. include:: explain_grd_inout_short.rst_

.. include:: explain_grd_coord.rst_

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
--------

:doc:`gmt`,
:doc:`grd2xyz`,
:doc:`grdinfo`
:doc:`xyz2grd`