FTN4,L
C 
C 
C 
C 
C 
C 
CC************************************************************
C (C) COPYRIGHT HEWLETT-PACKARD COMPANY 1978.  ALL RIGHTS    *
C RESERVED.  NO PART OF THIS PROGRAM MAY BE PHOTOCOPIED, RE- *
C PRODUCED, OR TRANSLATED TO ANOTHER PROGRAM LANGUAGE WITH-  *
C OUT THE PRIOR WRITTEN CONSENT OF HEWLETT-PACKARD COMPANY.  *
CC************************************************************
C 
C 
C 
C      NAME: GANG4
C      SOURCE: 92840 - 18163
C      RELOC:  92840 - 16021
C 
C 
C 
CC*********************************************************** 
      SUBROUTINE GANG4(IGCB,AMU,ANDC,BUFR)
     +,92840-16021 REV.2013 791129
C************************************************************** 
C GANG4 CONVERTS AN MU ANGLE INTO AN NDC ANGLE. 
C 
C AMU  = ANGLE IN MACHINE UNIT RADIANS. 
C ANDC= ANGLE IN NDC COORDINATE RADIANS. (RETURNED) 
C BUFR = MINIMUM 8-WORD UTILITY BUFFER. 
C************************************************************** 
      INTEGER IGCB(1) 
      REAL AMU,AMU,BUFR(1)
      REAL PI 
      INTEGER IREAD 
      DATA PI/3.14159/
      DATA IREAD/1/ 
C*************************************************************
C CALCULATE THE ANGLE IN NDC COORDINATES. THE ALGORITHM 
C IS AS FOLLOWS:
C 
      XMU=COS(AMU)
      YMU=SIN(AMU)
C***********************************************************
C GET THE CONVERSION FACTORS. 
C 
20    CONTINUE
      CALL GCBIM(11,1,BUFR,0,IREAD) 
C**************************************************************** 
C CONVERT TO NDC UNITS. 
C 
      XNDC=XMU/BUFR(1)
      YNDC=YMU/BUFR(3)
C**************************************************************** 
C TAKE THE ARCTAN TO GET THE MU ANGLE.
C CORRECT THE NDC ANGLE TO BE IN THE SAME QUADRANT AS THE MU ANGLE. 
C 
      ANDC=ATAN2(YNDC,XNDC) 
      RETURN
      END 
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