CALL SEQUENCE...
       subarea  XIN XOUT INPUT OUTPUT (TAPE45=pltinfo)
               [ -dlat1 VAL1  -dlon1  VAL2  -dlat2 VAL3  -dlon2 VAL4
                 -dgrw  VAL5  -lx     VAL6  -nhem  VAL7  -kind  VAL8
                -nintyp VAL9  -noutyp VAL10 ]
 
 
      DESCRIPTION...
       subarea - CONVERTS A GLOBAL OR HEMISPHERIC CARTESIAN GRID
                 TO A SMALLER AREA
  
 
      AUTHORS - M.Sutcliffe, R.Daley AND M.Lazare  AUG 10/87.
      LAST REVISION: $Header: /home/cvs/RMNLIB/utils/rdiag/lspgm/subarea.ptn,v 4.12 2014/09/25 20:20:54 dugas Exp $
 
  
      PURPOSE - CONVERTS A FILE OF GAUSSIAN OR LAT-LON GRIDS TO A FILE OF POLAR
                STEREOGRAPHIC, GAUSSIAN OR LAT-LON GRIDS REPRESENTATIVE OF A 
                SUB-AREA OF THE GLOBE, BY LINEAR OR CUBIC INTERPOLATION. 
 
      NOTE (which applies only to CCCma files...)
              - IN ADDITION TO XOUT AND THE OUTPUT FILE, SUBAREA ALSO 
                WRITES CO-ORDINATE INFORMATION TO "pltinfo" FILE 
                (UNIT 45) TO BE SUBSEQUENTLY USED BY GGPLOT. THIS
                NAME CANNOT BE REASSIGNED AND WILL RESIDE ON CURRENT
                DIRECTORY.
 
           ***  THE USER SHOULD CALL GGPLOT IMMEDIATELY AFTER SUBAREA 
                AND BEFORE CALLING SUBAREA AGAIN, (EXCEPT WHEN PLOTTIN 
                MULTIPLE FIELDS WITH A SINGLE CALL TO GGPLOT). 
 
  
      INPUT FILE...
       XIN  = FILE CONTAINING GAUSSIAN-GRID OR LAT-LONG FIELDS. 
  
 
      OUTPUT FILE...
       XOUT = FILE CONTAINING POLAR-STEREOGRAPHIC OR CARTESIAN FIELDS 
              REPRESENTING A SUB-AREA OF THE GLOBE. 
 
 
      PARAMETERS... 
  
       DLAT1,DLON1 = CARTESIAN COORDINATE IN DEGREES OF LOWER LEFT CORNER
                     OF PLOT. LATITUDES RANGE FROM -90 TO +90, FOR THE 
                     SOUTH AND NORTH POLES RESPECTIVELY. LONGITUDES RANGING
                     FROM -180 TO +180, WITH GREENWHICH MERIDIAN AT 0. 
       DLAT2,DLON2 = CARTESIAN COORDINATE IN DEGREES OF UPPER RIGHT CORNER
                     OF PLOT. COORDINATES NOT USED FOR DEFAULT P-S OUTPUT
       DGRW        = ANGLE OF GREENWHICH MERIDIAN OFF HORIZONTAL, 
                     NON-DEFAULT P-S OUTPUT ONLY. 
       LX          > 0, THE RESOLUTION OF THE INTERPOLATED P-S OUTPUT FILE
                        LX GRID POINTS ARE USED ALONG THE X-AXIS, WITH THE
                        SAME RESOLUTION USED ALONG Y-AXIS. 
                        VALUES OF 30 TO 110 ARE SUGGESTED. 
                   <=0, CHOOSES ONE OF THE DEFAULT P-S PROJECTIONS BELOW 
                   = 0, STANDARD POLAR STEREOGRAPHIC PROJECTION OVER N OR
                        S POLE BASED ON CHOICE FOR NHEM. 
                   =-1, DEFAULT NORTH AMERICAN      P-S SUB-AREA. 
                   =-2, DEFAULT ASIAN               P-S SUB-AREA. 
                   =-3, DEFAULT EUROPEAN            P-S SUB-AREA. 
                   =-4, DEFAULT AUSTRALIAN          P-S SUB-AREA. 
                   =-5, DEFAULT ARCTIC OR ANTARCTIC P-S SUB-AREA, BASED 
                        CHOICE FOR NHEM. 
                   USED ONLY FOR P-S GRID OUTPUT. 
       NHEM        =0,1 PLOT NORTH HEMISPHERE. 
                   = 2  PLOT SOUTH HEMISPHERE. 
                   USED FOR NON-DEFAULT P-S OUTPUT, AND WHEN LX= 0 OR -5 
                   IF XIN CONTAINS HEMISPHERIC DATA, THE DEFAULT NHEM
                   VALUE IS THEN THAT OF THE FIRST GRID IN XIN
       KIND        = 1,       USE LINEAR INTERPOLATION, 
                     2,       USE NEAREST NEIGHBORS (RPN/CMC FILES ONLY)
                   OTHERWISE, USE CUBIC INTERPOLATION (DEFAULT).
                   THIS PARAMETRE IS USED ONLY FOR P-S OUTPUT. 
       NINTYP      = 0,       INPUT FILE IS GAUSSIAN GRID, 
                   = 1,       INPUT FILE IS "B" LAT-LON  GRID,
                   = 2,       INPUT FILE IS "A" LAT-LON  GRID.
                   THIS PARAMETRE IS IGNORED FOR RPN/CMC FILES.
       NOUTYP      = 0, OUTPUT FILE IS ON A SUBSET OF THE INPUT CARTESIAN
                        GRID. CHOSEN COORDINATES ARE ADJUSTED TO THE 
                        NEAREST COORDINATES ON THE INPUT GRID. THE
                        OUTPUT THEN IS KNOWN AS A L-TYPE GRID.
                   OTHERWISE, OUTPUT FILE IS INTERPOLATED TO A P-S 
                        PROJECTION WITH RESOLUTION LX. 
  
      READ(5,5010) DLAT1,DLON1,DLAT2,DLON2,DGRW,LX,NHEM,KIND, 
     1             NINTYP,NOUTYP 
 5010 FORMAT(10X,5E10.0,3I5,1X,2I2) 
 
 
      EXAMPLE OF INPUT CARD... 
  
  SUBAREA.      -80.        5.       80.      179.      -10.    0    1 
 
         0123456789012345678901234567890123456789012345678901234567890
         1         2         3         4         5         6         7
 
 
      EXIT CONDITIONS...
        0 NO PROBLEMS
        1 ERROR READING FIRST ARRAY IN XIN
        2 MISMATCH BETWEEN NHEM AND IBUF(7)
        3 ENCOUNTERED ILLEGAL NEGATIVE LX VALUE
        4 BAD POLAR STEREOGRAPHIC GRID SPECIFICATION
        5 BAD LATITUDE-LONGITUDE GRID SPECIFICATION
        6 ERROR READING INPUT PARAMETERS
        7 PROBLEMS READING FILE PLTINFO
        8 MORE THAN ONE SIZE IN XIN
        9 UNSUPPORTED INPUT ARRAY