SUBROUTINE KVAVRG(Z1, VZ1, Z2, VZ2, Z3, VZ3, CHISQ)
C
C  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
C    Returns the weighted average of 2 vertices and the chisquare.
C    The vertices are assumed to be independent of each other.
C
C  Z1      real array (read)
C          (x,y,z) of first vertex
C
C  VZ1     real array (read)
C          3x3 covariance matrix of first vertex
C
C  Z2      real array (read)
C          (x,y,z) of second vertex
C
C  VZ2     real array (read)
C          3x3 covariance matrix of second vertex
C
C *Z3      real array (write)
C          (x,y,z) of averaged vertex
C
C *VZ3     real array (write)
C          3x3 covariance matrix of averaged vertex
C
C *CHISQ   real variable (write)
C          chisquare of combined vertex
C  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>