SUBROUTINE UNDEF(Z,NX,NY)
      DIMENSION Z(NX,NY)
      DO 1000   IX=1,NX
      DO 1000   IY=1,NY
      IF(Z(IX,IY).GE.1.0E30)   Z(IX,IY)=999.999
 1000 CONTINUE
      RETURN
      END