LONXLATE
Name
LONXLATE
Purpose
This function translates an array (or atomic element) of
longitudes from one grid to another. A grid is either Eastern or
Western longitude, and from 0 to 360 or -180 to 180
Category
Mapping
Calling Sequence
Result = LONXLATE( Longitudes, /from_xxx, /to_xxx )
Inputs
Longitudes: An array (or a atomic element (scalar)) of
longitudes. These must be valid regarding the /FROM_xxx grid
system.
Keyword Parameters
FROM_180E: A keyword specifying that the longitude(s) range
between -180 and 180, and increase to the East.
FROM_180W: A keyword specifying that the longitude(s) range
between -180 and 180, and increase to the West.
FROM_360E: A keyword specifying that the longitude(s) range
between 0 and 360, and increase to the East.
FROM_360W: A keyword specifying that the longitude(s) range
between 0 and 360, and increase to the West.
TO_180E: A keyword specifying that the output longitude(s) range
should be between -180 and 180, and increase to the East.
TO_180W: A keyword specifying that the output longitude(s) range
should be between -180 and 180, and increase to the West.
TO_360E: A keyword specifying that the output longitude(s) range
should be between 0 and 360, and increase to the East.
TO_360W: A keyword specifying that the output longitude(s) range
should be between 0 and 360, and increase to the West.
Outputs
This function returns the input longitude array, translated from
the grid specified by the /FROM_xxx keyword, onto the grid
specified by the /TO_xxx keyword.
Side Effects
None that I know of yet... Email me if you find any.
Restrictions
The input array must be valid on the grid specified by the
/FROM_xxx keyword. No error checking is done. Use CIRRANGE and/or
RANGECIR before calling this to fix your lons for you (they are in
the astronomy library)
Procedure
* read the code
* Most of the work is done in the /to_180e section. All other
/TO_xxx keywords use that chunk of code, pass in the /FROM_xxx
keyword, and then do only a little bit of work to translate from
/to_180e to the actual requested /TO_xxx.
Example
lon_0 = [ -135, -45, 45, 135 ]
lon_1 = lonxlate( lon_0, /from_180e, /to_180w )
lon_2 = lonxlate( lon_1, /from_180w, /to_360e )
Modification History
Written by: Ken Mankoff (mankoff@lasp.colorado.edu), 2002-04-03
2002-05-22; KDM; Added documentation.