	SUBROUTINE GRID_WORLD_EXTREMES ( lo, hi, grid, idim )

*
*
*  This software was developed by the Thermal Modeling and Analysis
*  Project(TMAP) of the National Oceanographic and Atmospheric
*  Administration's (NOAA) Pacific Marine Environmental Lab(PMEL),
*  hereafter referred to as NOAA/PMEL/TMAP.
*
*  Access and use of this software shall impose the following
*  obligations and understandings on the user. The user is granted the
*  right, without any fee or cost, to use, copy, modify, alter, enhance
*  and distribute this software, and any derivative works thereof, and
*  its supporting documentation for any purpose whatsoever, provided
*  that this entire notice appears in all copies of the software,
*  derivative works and supporting documentation.  Further, the user
*  agrees to credit NOAA/PMEL/TMAP in any publications that result from
*  the use of this software or in any product that includes this
*  software. The names TMAP, NOAA and/or PMEL, however, may not be used
*  in any advertising or publicity to endorse or promote any products
*  or commercial entity unless specific written permission is obtained
*  from NOAA/PMEL/TMAP. The user also understands that NOAA/PMEL/TMAP
*  is not obligated to provide the user with any support, consulting,
*  training or assistance of any kind with regard to the use, operation
*  and performance of this software nor to provide the user with any
*  updates, revisions, new versions or "bug fixes".
*
*  THIS SOFTWARE IS PROVIDED BY NOAA/PMEL/TMAP "AS IS" AND ANY EXPRESS
*  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
*  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
*  ARE DISCLAIMED. IN NO EVENT SHALL NOAA/PMEL/TMAP BE LIABLE FOR ANY SPECIAL,
*  INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
*  RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
*  CONTRACT, NEGLIGENCE OR OTHER TORTUOUS ACTION, ARISING OUT OF OR IN
*  CONNECTION WITH THE ACCESS, USE OR PERFORMANCE OF THIS SOFTWARE. 
*
*
* find the extreme bounds of the indicated grid on the indicated axis
* in WORLD coordinates
* programmer - steve hankin
* NOAA/PMEL, Seattle, WA - Tropical Modeling and Analysis Program
* written for VAX computer under VMS operating system
*
* revision 0.0 - 10/16/86
* revision 1.0 - 3/10/87  - changed to axis data stored in COMMON/~VARIABLES/
*			    and changed time axis dependence
* revision 1.1 - 2/18/88  - incorporated "regular" axes
* revision 1.2 - 20/12/88 - incorporated new TM IO library (no box sizes)
* revision 1.3 - 2/6/89   - added modulo axes of arbitrary length
* Unix/RISC port - 7/91   - eliminated unneeded *variables common
* V4.20 - 10/95 - remove references to line_mem to permit recursive line defs
*       *acm* 3/12 cleanup ifdefs and unnecessary include files
* V72   11/16 *acm* Ticket 2158: working with true monthly time axes.

	include 'tmap_dims.parm'
	include	'xtm_grid.cmn_text'
	external xgt_grid_data
	include	'ferret.parm'

* calling argument declarations
	INTEGER	grid, idim
	REAL*8	lo,hi

* local variable declarations
	LOGICAL ITSA_TRUEMONTH_AXIS
	INTEGER line_num, line_len
	REAL*8	TM_WORLD

	line_num = grid_line( idim, grid )
	line_len = line_dim( line_num )

	IF     ( line_num .EQ. mnormal  ) THEN

	   lo = unspecified_val8
	   hi = unspecified_val8

	ELSEIF ( line_num .EQ. munknown ) THEN

	   lo = arbitrary_small_val8
	   hi = arbitrary_large_val8

	ELSEIF ( line_modulo(line_num) ) THEN

	   lo = arbitrary_small_val8
	   hi = arbitrary_large_val8

	ELSE

	   IF ( line_regular( line_num ) .AND. .NOT.ITSA_TRUEMONTH_AXIS (line_num)) THEN
	      lo = line_start( line_num ) - line_delta( line_num )/2.
	      hi = lo + line_delta( line_num ) * line_dim( line_num )

	   ELSE
* ... lo limit of bottom box; hi limit of top box
	      lo = TM_WORLD(       1, grid, idim, box_lo_lim)
	      hi = TM_WORLD(line_len, grid, idim, box_hi_lim)

	   ENDIF

	ENDIF

	RETURN
	END

