ADAS Subroutine linfit

       SUBROUTINE LINFIT(X,XSA,Y,YSA,ICT)                               
C
       IMPLICIT REAL*8(A-H,O-Z)                                         
C-----------------------------------------------------------------------
C
C  ****************** FORTRAN77 SUBROUTINE: LINFIT *********************
C
C PURPOSE:
C  SUBROUTINE TO PERFORM LINEAR INTERPOLATION                           
C
C
C  INPUT
C      X     = REQUIRED X-VALUE
C      XSA(I)= X-VALUES
C      YSA(I)= Y-VALUES
C      ICT   = NUMBER OF VALUES
C  OUTPUT
C      Y     = RETURNED Y-VALUE
C
C NOTES: THIS ROUTINE IS NOT YET PROPERLY ANNOTATED
C
C UNIX-IDL PORT:
C
C VERSION: 1.1                          DATE: 06-03-96
C MODIFIED: TIM HAMMOND (TESSELLA SUPPORT SERVICES PLC)
C               - PUT UNDER S.C.C.S. CONTROL
C
C-----------------------------------------------------------------------
C
      INTEGER             ICT
      REAL*8              X,           XSA(10),     Y,           YSA(10)