GDSII stream reading
AREFS are the same as SREFS except the entire array lattice is reflected:


  STRANS [1A01]     Bit array: contains two bytes of bit flags for SREF,
  AFREF, and text transformation. Bit 0 (leftmost) specifies reflecton.
  If it is set, then reflection about the X axis is applied before
  angular rotation. For AREFs, the entire array lattice is reflected,
  with the individual array elements riidly attached. Bit 13 flags
  absolute magnification. Bit 14 flags absolute angle. Bit 15
  (rightmost) and all remaining bits are reserved for future use and
  must be cleared. If this record is omitted, then the element is
  assumed to have no reflection and its magnification and angle are
  assumed to be non-absolute.  


Source http://www.artwork.com/gdsii/gdsii/page5.htm

See also this link in the SPIE Handbook