C
C***********************************************************************
C                 COPYRIGHT ATLANTIC RICHFIELD COMPANY 1991            *
C***********************************************************************
CTITLESAPHZFT -- DETERMINE THE PHASE INTERCEPT                          00010001
CA    AUTHOR       B. S. BOK                                            00030001
CA    DESIGNER     B. S. BOK                                            00040001
CA    LANGUAGE     FORTRAN                                              00050001
CA    SYSTEM       IBM / CRAY                                           00060004
CA    WRITTEN      AUGUST, 1990                                         00070001
C     REVISED      12-21-91 JJC - MODIFIED TO MEET EDP STANDARDS.
C
CA                                                                      00150001
CA    CALL SAPHZFT (AMP, PHZ, NYQ, CUT, ICODE, PHI, DLAY, WRK)          00160004
CA                                                                      00180000
CA         INPUT   AMP    = AMPLITUDE SPECTRUM (LENGTH OF NYQ)      R4  00190003
CA         INPUT   PHZ    = PHASE UNWRAPPED SPECTRUM (SIZE OF NYQ)  R4  00200003
CA         INPUT   NYQ    = NYQUIST NO. OF SAMPLES                  I4  00210003
CA         INPUT   CUT    = CUT LEVEL OF AMPLITUDE TO BE USED       R4  00200003
CA         INPUT   ICODE  = 0 => AMPLITUDE WEIGHTING                I4  00210003
CA                        .NE. 0 => POWER WEIGHTING
CA         OUTPUT  PHI    = PHASE INTERCEPT DETERMINED              R4  00260007
CA         OUTPUT  DLAY   = TIME DELAY OR SLOPE OF TANGENTIAL LINE  R4  00270004
CA                          (TIME SAMPLES); IF NYQ IS NOT NYQ
CA                          FREQUENCY, MULTIPLY (1-NYQF) / (1-NYQ)
CA         OUTPUT  WRK    = WORK ARRAY OF SIZE AT LEAST NYQ         R4
CA                                                                      00340000
CA                                                                      00350000
CA    THIS ROUTINE DETERMINE THE PHASE INTERCEPT OF TANGENTIAL LINE AT  00360001
CA    PHASE SPECTRUM                                                    00370001
CA                                                                      00510000
C**************************************************************
C                                                             *
C SUBROUTINES AND FUNCTIONS CALLED FROM THIS ROUTINE          *
C                                                             *
C SATAYL2                                                     *
C                                                             *
C**************************************************************
C
      SUBROUTINE SAPHZFT (AMP,PHZ,NPT,CUT,ICODE,PHI,SLPE,WRK)
C
      IMPLICIT INTEGER (A-Z)
C
      REAL   AMP
      REAL   CUT
      REAL   F
      REAL   HOLD
      REAL   PHI
      REAL   PHZ
      REAL   SLPE
      REAL   WRK
C
      DIMENSION AMP(NPT), PHZ(NPT), WRK(NPT), F(10)
C
C     RANGE OF FREQUENCY TO BE USED
C
      MIN = 1
      MAX = NPT
      IF (CUT .GT. 0.) THEN
         HOLD = 0.
         DO 100 N = 1, NPT
            IF (HOLD .LT. AMP(N)) THEN
               HOLD = AMP(N)
               MAX = N
            ENDIF
 100     CONTINUE
         HOLD = HOLD * CUT
         DO 120 N = 1, MAX
            IF (AMP(MAX - N + 1) .LE. HOLD) GO TO 140
 120     CONTINUE
         N = MAX
 140     CONTINUE
         MIN = MAX - N + 1
         DO 160 N = MAX, NPT
            IF (AMP(N) .LE. HOLD) GO TO 180
 160     CONTINUE
         N = NPT
 180     CONTINUE
         MAX = N
      ENDIF
C
C     PHASE CURVE BY AMPLITUDE OR POWER WEIGHTING
C
      DO 200 N = MIN, MAX
         WRK(N) = N - 1
 200  CONTINUE
      MAX = MAX - MIN + 1
      CALL SATAYL2( WRK(MIN), PHZ(MIN), AMP(MIN), MAX, ICODE, 2, F, WRK(
     1   NPT + 1) )
      PHI = F(1)
      SLPE = F(2)
C
C
      RETURN
      END