CALL SEQUENCE...
       zxdlatf  ZXIN ZXOUT OUTPUT
 
 
      AUTHOR  - J.D.Henderson, NOV  7/80.
      LAST REVISION: $Header: /home/cvs/RMNLIB/utils/rdiag/lspgm/zxdlatf.ptn,v 4.10 2014/09/25 20:20:57 dugas Exp $
 
 
      PURPOSE - READS 'G', 'A' OR 'B' GRID CROSS-SECTIONS FROM FILE ZXIN,
                COMPUTES THE LATITUDE DERIVATIVE OF THE CROSS SECTIONS
                USING FINITE DIFFERENCES AND PUTS THE RESULT ON FILE
                ZXOUT. TYPE 'G' (GAUSSIAN) IS ASSUMED FOR CCRN FILES.
 
      NOTE    - MAX LATITUDES/LEVELS IS 999.
 
 
      INPUT FILE...
       ZXIN  = GLOBAL OR HEMISPHERIC CROSS-SECTIONS.
 
      OUTPUT FILE...
       ZXOUT = LAT DERIVATIVES
 
 
      EXIT CONDITIONS...
        0 NO PROBLEMS
        1 TOO MANY OR NOT ENOUGH LEVELS IN ZXIN
        2 FOUND UNSUPPORTED DATA TYPE IN ZXIN
        3 ABORT ERROR READING ZXIN