SUBROUTINE DERIVE_TREE_OFFSETS ( LOOKUP_QUANT )
C----------------------------------------------------------------------
C-
C-   Purpose and Methods : Builds the global tree offset by summing the
C-                         individual tower offsets over the whole detector.
C-
C-   Inputs  :          quantity type, cf. parameters in level1_lookup.params
C-                      common block level1_lookup.inc
C-   Outputs :          tree_offset, in level1_lookup.inc
C-
C-   Created   6-AUG-1990 MICHIGAN STATE UNIVERSITY, TRIGGER CONTROL SOFTWARE
C-
C----------------------------------------------------------------------
      IMPLICIT     NONE 
C      
      INCLUDE     'D0$LEVEL1:LEVEL1_LOOKUP.PARAMS'
      INCLUDE     'D0$LEVEL1:LEVEL1_LOOKUP.INC'
C
      INTEGER      LOOKUP_QUANT
      INTEGER      SIGN_ETA, MAGN_ETA, PHI
C
C----------------------------------------------------------------------
C
      TREE_OFFSET ( LOOKUP_QUANT ) = 0
C
      DO PHI = PHI_MIN, PHI_MAX
       DO MAGN_ETA = ETA_MIN, ETA_MAX
        DO SIGN_ETA = POS_ETA, NEG_ETA
C
C          increment tree offset
          TREE_OFFSET (LOOKUP_QUANT) = TREE_OFFSET (LOOKUP_QUANT) 
     &          + LOOKUP_ZERESP (SIGN_ETA,MAGN_ETA,PHI,LOOKUP_QUANT) 
C
        END DO
       END DO
      END DO
C
C----------------------------------------------------------------------
  999 RETURN
      END
C